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Research Article                                                                                                                                        Open Access

## A Danish study of One-session Treatment for Specific Phobias in Children and Adolescents

Mette Djernes Nielsen, Christina Linddahl Andreasen, Mikael Thastum*

Department of Psychology and Behavioural Sciences, Aarhus University, Denmark

*Corresponding author: mikael@psy.au.dk

## Abstract

Background: One-session treatment (OST) is a short-term massed exposure therapy for the treatment of specific phobias in children and adults. Systematic reviews have demonstrated the effectiveness of the treatment for children and adolescents across countries and age groups.

Objective: A single-group open trial design was used to examine the feasibility and preliminary efficacy of OST for youths with specific phobias in a Danish context.

Method: At the Anxiety Clinic of Aarhus University, 10 youths between the ages of 7 and 17 years who fulfilled the diagnostic criteria  for  specific  phobias  were  treated  in  accordance  with  the  OST  manual.  The  participants  were  assessed  via  semistructured diagnostic interviews, clinician severity ratings, a behavioral approach test, and self- and parent report measures. Feasibility was assessed with the use of patient- and parent-report measures. Assessments were completed at before and after treatment and at the 3-month follow-up appointment.

Results: All outcome measures changed significantly from the pretreatment period to the 3-month follow-up assessment. Four (40%) of the participants were free of the targeted specific phobia after treatment, and eight (80%) were free of the phobia at the 3-month follow-up. The families were moderately satisfied with the treatment, and no patients dropped out of the study.

Conclusion: On the basis of the results of this pilot study, it may be tentatively concluded that OST could be useful for the treatment of youths with specific phobias in Denmark.

Keywords: specific  phobias;  children  and  adolescents;  cognitive  behavioral  therapy;  one-session  treatment;  treatment outcome

## Introduction

Specific phobias are one of the most frequent mental disorders among children and adolescents (hereafter referred  to  as youths ),  with  a  lifetime  prevalence  of 12.5% and a mean age of onset of 7 to 9 years (1). As a result of the high prevalence of this condition and the fact that specific phobias may interfere with daily functioning, there is a need to develop and enhance efficacious treatments. Furthermore, phobias during childhood may be a significant predictor of anxiety disorders later in life (2), so it may be important to start treatment as soon as possible.

The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), categorizes specific  phobias  into  five  subtypes:  animal  type, natural environment type, blood-injection-injury type,  situational  type,  and  other  type  (e.g.,  loud noises)  (3).  The  most  frequently  occurring  phobia types in children and adolescents are the animal type and the natural environment type (4).

The most frequent comorbid anxiety disorders in youth with specific phobias are post-traumatic stress disorder, obsessive-compulsive disorder, and anxiety not  otherwise  specified;  however,  other  comorbid disorders are common as well (5). Fifty percent of youth with specific phobias suffer from at least one other specific phobia, and 25% suffer from another mental disorder (6).

One-session treatment (OST) is a 3-hour massed single-session graduated exposure variant of cognitive behavioral therapy (CBT) for the treatment of  specific  phobias  (7).  The  treatment  is  based  on evidence-based  methods such  as  in  vivo  exposure, cognitive restructuring, psychoeducation, participant modeling,  and  reinforced  practice.  OST  has  been used to treat adults with specific phobias, and it has demonstrated positive long-term results over a 7.5year period, with 65% of treated patients diagnosisfree and an additional 25% improved (7). Within the last decade, systematic reviews have also demonstrated  the  effectiveness  of  OST  for  the treatment of youth across different phobias, formats, countries, and age groups (8-10). Zlomke and Davis (8) found small to large uncontrolled effect sizes for OST from before to after treatment for the primary outcome measures of self-reports and observations of anxiety level. A systematic review by  Davis and colleagues (10) concluded that OST demonstrated a significantly better treatment effect as compared with alternative treatments (e.g., eye movement desensitization and reprocessing, psychological placebo). On the basis of a narrative review of eight studies supporting the well-established status of OST for  children  with  specific  phobias,  Ollendick  and Davis  (9)  concluded  that  OST  is  the  treatment  of choice  for  children  with  specific  phobias.  Nielsen (11)  investigated  the  effect  of  OST  and  found moderate  to  large  ( d =  0.6  to  3.26)  uncontrolled effect sizes for the primary outcome measures from before to after treatment. Furthermore, when OST was  compared  with  other  active  treatments,  the controlled effect sizes of the outcome measures were small to moderate ( d = 0.30 to 0.56), whereas small to  large  effect  sizes  ( d = 0.15 to 3.39) were found when  comparing  OST  with  waitlisting.  Fifty-four percent of the clients treated  with  OST  were diagnosis-free after treatment.

OST  has  been  found  to have an effect on comorbid  disorders  even  though  they  are  not  the target  of  the  treatment.  Ost  and  colleagues  (12) randomized  60  youths  to  three  conditions:  OST alone, OST with a parent present, or waitlisting. They found that the two OST  conditions produced significant  reductions  in  the  clinical  severity  rating (CSR)  of  the  comorbid  disorders.  Ollendick  and colleagues (13) used data from an existing randomized  controlled  trial  of  OST  to  examine whether  the  treatment  outcome  was  affected  by  a patient's comorbid disorders and whether the treatment of the specific phobia had an effect on the co-occurring  disorders.  Results  indicated  that  the presence  of  comorbid  phobias  and  other  anxiety disorders did not influence the treatment effect and that OST  reduced the clinical severity of the comorbid specific phobias and other anxiety disorders not targeted by the treatment.

Homework  in  the  form  of  rehearsing  the  skills acquired during therapy in the youth's natural environment is considered an important ingredient for maintaining or increasing treatment gains (14). A meta-analysis (15) found that the treatment of adults that included homework assignments yielded significantly better post-treatment outcomes as compared with treatment without homework, with a small controlled effect size ( d = 0.48). However, the few studies of these effects  in  youths  have  yielded mixed  results.  Hughes  and  Kendall  (16)  found  no significant associations between homework compliance  and treatment outcomes  when  treating youths  with  mixed  anxiety  disorders.  Arendt  and colleagues  (17)  investigated  different  associations between  homework  and  treatment  outcomes  and found no convincing evidence that  homework compliance was related to the treatment outcomes of a  CBT  program  for  youths  with  mixed  anxiety disorders.  Alternatively,  Park  and  colleagues  (18) found a  significant  association  between  homework compliance  and  outcome  in  a  CBT  program  for youths with a primary diagnosis of obsessivecompulsive disorder.

To  produce  better  treatment  outcomes,  some studies  have  investigated  the  effect  of  adding  a booster session to CBT. A recent meta-analysis of 53 studies that included a total of 1937 youths showed that CBT interventions that included booster sessions  were  more  effective  than  CBT  treatments without  booster  sessions  for  youths  with  anxiety disorders (19). Pretreatment and post-treatment studies  with  booster  sessions  showed  significantly larger  effect  sizes  ( r =  .58)  than  studies  without booster sessions ( r = .45). The researchers hypothesized  that  the expectation  of a  booster session  may  exert  an  anticipatory  effect  on  youth outcomes  before  the  start  of  the  actual  booster sessions. Similarly, pretreatment to follow-up studies that involved booster sessions showed a significantly larger  effect  size  ( r =  .64)  than  studies  without booster  sessions  ( r =  .48)  after controlling  for demographic factors, primary diagnosis, and intervention characteristics (e.g. treatment modality, number of sessions). The effect of adding a booster session to the OST manual has not been investigated yet.

## Method

Participants

The participants were 10 youths (nine girls, one boy) with specific phobias who were between seven and 17 years old (mean [M], 10.5 years; standard deviation [SD], 3.0 years). They were recruited from the waiting list  and  via  the  website  of  the  Anxiety  Clinic  for Children  and  Adolescents  at  Aarhus  University, Denmark, and  via  the  website  of  Angstforeningen

(The Danish Anxiety Society). The first 10 children and adolescents who applied for treatment and who met  the  DSM-IV  criteria  for  specific  phobia  were included  in  the  study.  The  inclusion  criteria  were being between seven and 17 years old and having a specific phobia diagnosis in accordance with DSMIV. The exclusion criteria were as follows: 1) having a  current  diagnosis  of  severe  behavioral  disorder, untreated attention-deficit/hyperactivity disorder, selective mutism, autism spectrum disorder, intellectual disability, psychotic disorder, eating disorder  requiring  treatment,  substance  abuse,  or depression; and 2) receiving other current treatment (psychotherapy or medical). The study was approved by the Ethical Committee of the local county and by the  Danish  Data  Protection  Agency.  All  parents signed  written  consent  forms  after  the  family  had been given oral and written information about the treatment and before the youths began the treatment. The treatment was offered for free and took place at the Anxiety Clinic for Children and Adolescents at the  Department  of  Psychology  and  Behavioural Sciences, Aarhus University, Denmark.

## Assessment

Assessment before treatment

Each  youth's  motivation  for  the  treatment  was assessed on the basis of a shortened version of the Nijmegen Motivation List (20), which was developed by Ollendick and colleagues (21). This version has 15 items that include statements such as ' I believe that this is the right treatment for me' and 'I'm certain that I will also practice at home the things I learn in treatment.' The statements are rated from 0 (not at all true) to 2 (mostly true). The results range from 0 to 30, and scores of less than 15 are considered to represent  youths  with  poor  motivation.  Ollendick and colleagues (21) found an internal consistency of 0.73.  In  the  present  study,  the  Cronbach's  alpha coefficient was 0.65.

The parent's credibility and expectations in relation to the treatment were assessed with the Credibility/Expectancy  Questionnaire  (22),  which consists of four questions regarding what the parent thinks about the treatment and two questions regarding what the parent feels about the treatment. The credibility  subscale  was  derived  from  the  first three  'think'  questions  (e.g.,  'At  this  point,  how successful  do  you  think  this  treatment  will  be  in reducing your child's anxiety symptoms?'), and the expectancy  subscale  was  derived  from  the  fourth 'think' question and the two 'feel' questions (e.g., 'How much do you think that your child's anxiety symptoms  will  have  improved  by  the  end  of  the therapy period?'). Four of the items were rated on scales that ranged from  1 (not at all logical/ useful/confident) to 9 (very logical/useful/

confident), and the other two were rated on an 11point scale from 0% to 100%. During the scoring of the  questionnaire,  the  11-point  scale  items  were recoded to make them comparable with the 9-point scale items. During the recoding process, values from 40% to 60% on the 11-point scale were merged into one value that corresponded with 5 on the 9-point scale.  This  way  of  scoring  the  questionnaire  is consistent  with  how  the  questionnaire  has  been scored in other studies (23). A total score between 3 and  27  for  each  subscale  was  calculated  for  the mothers  and  fathers,  with  higher  scores  indicating high credibility  and  positive  expectations  regarding the  treatment.  The  whole  scale  has  a  Cronbach's alpha coefficient between 0.84 and 0.85. The 1-week test-retest reliability was found to be good for both the expectancy ( r = 0.82) and the credibility ( r = 0.75) questionnaire  (22).  In  this  study,  the  Cronbach's alpha  coefficient  of  the  whole  scale  was  0.93  for mothers and 0.91 for fathers.

## Outcome measures

The Anxiety Disorders Interview Schedule for DSMIV, Child and Parent Versions (ADIS-IV-C/P) (24) is  a  semi-structured  diagnostic  interview  for  the assessment of anxiety, including specific phobia, in children and adolescents. Interviews are conducted separately for the youths and their parents. For the ADIS-IV-C/P, all diagnoses are given a CSR from 0 (no symptoms) to 8 (very severe), with a rating of 4 or higher suggesting a clinical level of interference by the  specific  phobia  or  other  assessed  disorders. Separate  CSRs  are  made  by  youth,  parents,  and clinicians; in this study, only the clinicians' CSRs are reported.

The ADIS-IV-C/P interviews were conducted by the first and second authors of this study, who were master's  students  at  the  clinic.  They  were  both trained in the use of the ADIS-IV-C/P. The training consisted of watching two gold standard interviews on video, observing two live interviews, and conducting one satisfactory ADIS-IV-C/P interview with  a  client  while  an  experienced  ADIS-IV-C/P assessor observed. Both authors had also conducted several ADIS-IV-C/P interviews before working on this  study. They conducted the pretreatment, posttreatment,  and  follow-up  ADIS-IV-C/P  interviews for  the  youths  that they  did  not  treat  with  therapy (each student was the therapist for 5 children). They received supervision during all of their interviews at all time points from a clinician at the clinic who did not take part in the treatment.

The ADIS-IV-C/P has shown acceptable 7- to 14day test-retest reliability for the children and parents combined  ( K =  0.62 to 1.00) (25). Inter-rater reliability has been found to be acceptable for parent interviews ( K = 0.77) (26). The diagnosis of specific phobia  with  the  ADIS-IV-C/P  is  convergent  with high scores on the Fear Survey Schedule for Children, Revised (27). To assess the reliability of the specific  phobia  diagnosis  for  which  a  youth  was receiving treatment, independent assessors reviewed the  videotaped  interviews.  There  was  agreement about diagnosis for nine (90%) of the 10 children, and the interclass correlation coefficient for the CSR of the specific phobia diagnosis was 0.65.

The Behavioral Approach Test (BAT) is a therapist-engineered  controlled  situation  in  which the participant has to approach the feared stimulus. The  BAT  can  be  used  as  an  objectively  observed measure of the avoidance of the feared stimulus (28); it was used for this purpose in earlier studies of the effectiveness  of  the  OST  (12,21).  Ollendick  and colleagues (21) found a test-retest reliability of 0.87 for the percentage of steps undertaken in the BAT.

A  specific  BAT  was  made  for  each  of  the  four specific phobias included in the study: dogs, darkness, heights,  and  being  alone.  Each  BAT consisted of 11  or 12  steps  during  which  the participants  were  gradually  exposed  to  the  feared stimulus. To provide a reliable measure of the degree of avoidance, the participants were instructed to go as far as they could. However, they were also told that they  could  stop  at  any  time  if  they  became  too anxious. The participants were further instructed to stay at the stopping point, where they were asked to rate their subjective units of distress. The therapist did not interfere during the BAT.

Because the number of steps varied from one BAT to  another,  the  percentage  of  completed steps  was used for analysis. This kind of analysis has been used in  other  studies  (12,21).  All  of  the  BATs  were performed in vivo, using live dogs or live situations (i.e.,  a  dark room, balconies at different levels, and being alone).

The Fear Thermometer is a scale that ranges from 0 (not at all) to 8 (very much) and that can be used to rate the individual's degree of fear at different time points  (29).  The  Fear  Thermometer  was  used  to measure the participant's subjective units of distress during  the  BAT:  before  entering  the  BAT,  at  the stopping  point,  and  10  minutes  after  the  BAT. Ollendick  and  colleagues  (21)  found  a  test-retest reliability of 0.92 for the Fear Thermometer.

The  Fear  Survey  Schedule  for  Children,  Revised (FSSC-R), is a self-report measure in which youths rate their fear of 80 different objects or situations on a  3-point  scale  ('none',  'some'  or  'a  lot').  High scores  on  the  FSSC-R  indicate  the  presence  of significant fear and the possible presence of specific phobia. Weems and colleagues (30) found that the FSSC-R is useful for differentiating among types of phobias. The internal reliability (α = 0.96) and the 1week test-retest reliability ( r = 0.90) for this measure are  high  (31).  In  addition,  the  FSSC-R  has  been found to be stable over time (32). In this study, the Cronbach's  alpha  coefficient  of  the  FSSC-R  was 0.97.

The Self-Efficacy Questionnaire for Children (SEQ-C)  contains  24  items  that  represent  three domains of self-efficacy: 1) social self-efficacy (perceived capability to be included in peer relationships);  2)  academic  self-efficacy  (perceived capability to master  academic  subjects); and  3) emotional self-efficacy (perceived capability to cope with negative emotions). Each item is scored on a 5point scale from 1 (not at all) to 5 (very well) (33). The internal consistency reliability of the total selfefficacy  score  is  satisfactory  (α  =  .88)  (33).  In  this study, the Cronbach's alpha coefficient was 0.78.

At  the  3-month  follow-up,  the  youth  and  the parents  were  asked  how  much  time  the  youth had spent practicing confronting the specific phobia on a daily  basis  since  the  completion  of  treatment.  The answer categories were 0, 5, 10, 20, 30, 40, 50, and 60 minutes and more than 60 minutes. The last category (more than 60 minutes) was not used by any raters. This questionnaire will hereafter be referred to as the Estimated Amount of Training (EAT).

The  youths  and  their parents were  asked  to complete  the  Experience  of  Service  Questionnaire developed by the Anxiety Clinic at Aarhus University and inspired by the work of Attride-Stirling (34). This questionnaire assesses both youth and parent satisfaction with the treatment after treatment completion. Both the youths and their parents were asked to rate nine statements regarding their experience with the treatment as 0 (not true), 1 (partly true),  or  2  (true).  They  were  also  asked  to  rate whether, in their opinions, the anxiety and avoidance of the youth changed from before to after treatment on  a  scale  from  1  (a  lot  worse/more)  to  7  (a  lot better/less). The parents were asked to quantify any improvement they saw in the anxiety symptoms of their children. In addition, the parents were asked if there was something that they liked or disliked about the treatment and if there was anything that could be improved.

## Procedure

Table 1 provides an overview of the measures used in the treatment process and the time points at which they were administered.

## Procedure before treatment

After  a  youth  had  been  referred  to  the  study,  a therapist performed a preliminary screening by phone  with  the  youth's  parents.  If  the  parents' description of the symptoms passed the screening, an appointment for the diagnostic interview was made, and information about the study was mailed to the family. At the first meeting, the child and the parents were separately interviewed using the ADIS-IV-C/P, and  the  family  signed  the  informed  consent  form. Electronically administered rating scales (i.e., ADIS-IV-C/P, Anxiety Disorder Interview Schedule for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition , Child and Parent versions; BAT, Behavioral Approach Test; CEQ, Credibility/Expectancy Questionnaire; CSR, Clinical Severity Rating; EAT, Estimated Amount of Training; ESQ, Experience of Service Questionnaire; FSSC-R, Fear Survey Schedule for Children, Revised; FT, Fear Thermometer; NML, Nijmegen Motivation List; SEQ-C, Self-Efficacy Questionnaire for Children

TABLE 1. Summary of the Study Measures

|           | Measure                   | Intake   | Before Treatment   | After Treatment   | 3-Month Follow-up   |
|-----------|---------------------------|----------|--------------------|-------------------|---------------------|
| Parent    | ADIS-IV-C/P about child   | X        |                    | X                 | X                   |
| Youth     | ADIS-IV-C/P about self    | X        |                    | X                 | X                   |
| Clinician | ADIS-IV-C/P (CSR)         | X        |                    | X                 | X                   |
| Youth     | NML                       | X        |                    |                   |                     |
| Parent    | CEQ                       | X        |                    |                   |                     |
| Youth     | BAT                       |          | X                  | X                 | X                   |
| Youth     | FT                        |          | X                  | X                 | X                   |
| Youth     | FSSC-R                    | X        |                    | X                 | X                   |
| Youth     | EAT                       |          |                    |                   | X                   |
| Parent    | EAT                       |          |                    |                   | X                   |
| Youth     | ESQ                       |          |                    | X                 |                     |
| Parent    | ESQ                       |          |                    | X                 |                     |
| Parent    | Demographic questionnaire | X        |                    |                   |                     |
| Youth     | SEQ-C                     | X        |                    | X                 | X                   |

## Procedure after treatment and at follow-up

One week after treatment and at the 3-month followup, the child and the parents were interviewed using a reduced version of the ADIS-IV-C/P that included only  sections  for which  the  youth  fulfilled the diagnostic criteria at the pretreatment screening. The families filled in the self-report forms after treatment and at the 3-month follow-up. After treatment, the family  was  asked  about  their  experience  with  the treatment using the Experience of Service Questionnaire. At the 3-month follow-up, the family was also asked to complete the EAT. The participants  who  did  not  respond to  the  treatment were offered additional group or individual treatment in the clinic.

## Therapists

The  first  and  second  authors  of  this  study  were therapists  and  master's  students  at  the  clinic.  They had attended a seminar on OST given by Lars-Goran Ost, but they had no prior experience treating youths with specific phobias using the OST  manual. However, as part of the master's program in psychology, the therapists had been providing supervised treatment to youths with specific phobias and other anxiety disorders for a year using the Cool Kids Program at the Anxiety Clinic, Aarhus University.

## Treatment

The  youths  were  treated  for  specific  phobias  of darkness (n = 4), dogs (n = 4), heights (n = 1), and being alone (n = 1). The treatment consisted of four parts: a pretreatment meeting, a treatment session, a post-treatment meeting, and a booster session. The first three parts followed the manual for OST (35), and the booster session was added for this study.

## Pretreatment

One week before the treatment session, the therapist and the youth met for a clinical interview that lasted 45 to 60 minutes. The pretreatment plan was based on the Functional Assessment Worksheet developed by Davis and colleagues (36). The  youth was encouraged  to describe his or her catastrophic cognitions, maintaining factors, previous exposures, and  stimulus  characteristics.  A  fear  hierarchy  was developed  in  collaboration  between  the  youth  and the therapist, and the rationale and the content of the treatment were explained to the youth. It was made clear that the treatment was a joint effort between the therapist  and  the  youth.  The  therapist  assured  the youth  that  he  or  she  would  not  be  exposed  to  a stimulus  without  prior  warning.  At  the  end  of  the session, the BAT was carried out.

Nijmegen  Motivation  List,  Credibility/Expectancy Questionnaire, FSSC-R, and SEQ-C) were e-mailed to  the  families  to  be  completed  before  their  first appearance at the clinic and at all assessment points.

## Treatment session

The outcome goal of the treatment session was that the youth would be able to handle situations that he or  she  could  not  cope  with  before  the  treatment because of the specific phobia. The OST was used to show the youth that the dreaded consequences that he or she expected to happen when exposed to the feared  stimulus  or  situation  actually  did  not  occur. This was done through controlled exposure of the youth to the feared stimulus or situation. The main element  of  the  treatment  was  the  massive  in  vivo exposure,  during  which  the  youth's  catastrophic cognitions were confronted in gradually more challenging behavioral experiments. The youth had to  stay  in  the  situation  until  his  or  her  anxiety decreased at least 50%  according to the Fear Thermometer  and  preferably  until  it  had  vanished completely. It was important that the youth not be pushed into unexpected exposures. Rather, the youth and therapist continuously worked together on the next step. If it was helpful for the youth, the therapist could perform a step before the youth did as part of the exposure. The treatment session was limited to three hours.

## Post-treatment

One week after the treatment session, the youth and therapist met again. The youth was asked to repeat the rationale of the treatment and to remember how the  rationale  was  connected  to  the  phobia.  The treatment session was summed up by looking back at what the youth's problem looked like before treatment  and  how  the  catastrophic  thoughts  had gradually changed during the session. Furthermore, the youth was told that it is important to continue working with the skills achieved during the treatment for the next 6 months to maintain treatment gains. At the end of the meeting, instructions for how to deal  with  potential  setbacks  were  given.  The  posttreatment session lasted 30 to 45 minutes.

## Booster session

Three months  after the treatment session, the therapist, the youth, and the parents met for the last time. The therapist asked the family how successful the training had  been  since the post-treatment session and if they had experienced any difficulties with  continuing  the  training.  If  the  family  had forgotten or did not understand specific elements of the treatment, these elements were explained again. The booster session is not a part  of  Ost's  original program (7), but it was included in the present study because it was hypothesized that a booster session would improve homework compliance and thereby increase treatment gains.

## Statistical analysis

Within-group changes in the primary outcome measures  and  the  SEQ-C  scores  from  the  three points in time were examined to evaluate treatment effects. Not all of the data were normally distributed. However, because the parametric paired samples t -test  yielded  results  similar  to  the  non-parametric alternative Wilcoxon signed-rank test, the results of the  parametric  test  are  reported.  Effect  sizes  were calculated with the use of Cohen's d (37) . Remission rates were examined using percentages.

Stepwise multiple regression analyses were conducted with the total ADIS-IV-C/P CSR scores at the 3-month follow-up as the criterion variables. The post-treatment total ADIS-IV-C/P CSR criterion variable was inserted as the first step, and EAT  was  inserted  as  the  second  step.  Separate analyses  were  conducted  on  the  basis  of  the  EAT reports  of  each  youth  and  his  or  her  mother  and father.  Analyses  were  based  on  all  10  participants. Because the mother of one of the youths (Patient ID no.  6)  reported  an  EAT  far  higher  than  either  the father or the youth, the mother's score was interpreted  as  an  error  and  replaced  by  the  same score  that  the  youth  had  reported.  All  statistical analyses  were  carried  out  using  Statistical  Product and Service Solutions software version 20.

## Results

All  participants  completed the treatment, including the  post-treatment  and  follow-up  sessions.  Thus, there were no dropouts from treatment.

At the pretreatment assessment, the youths had an average of 3.6 anxiety diagnoses (SD, 3.4). Six of the 10 participants had at least one additional disorder besides the specific phobia. Two of the youths had other specific phobias, and the other four had three or more comorbid anxiety disorders. The diagnoses included  other  specific  phobias  [14],  generalized anxiety disorder [4], social phobia [3], and separation anxiety  disorder  [2].  An  overview  of  the  specific disorders of each participant is presented in Table 2.

The  youths'  motivation  score  on  the  shortened version of the Nijmegen Motivation List had a mean of 22.5  (SD,  3.1;  range,  16  to  27)  out  of  the  possible maximum  of  30  points. Because none  of the participants' scores were less than 15, all participants were  considered  to  be  motivated  to  complete  the treatment (21).

The credibility of the treatment was relatively high for the mothers (M, 20.2; SD, 3.6) and the fathers (M, 19.6;  SD,  4.0),  with  a  maximum  score  of  27.  The expectancy score was moderate for the mothers (M, 16.0; SD, 5.0) and the fathers (M, 17.0; SD, 4.2), also with a maximum score of 27. One question-'How much  do  you  expect  that your child's anxiety symptoms  will  have  improved  by  the  end  of  the treatment?'-was  analyzed  separately  to  compare the expected improvement before treatment with a similar  question  asked  after  treatment,  when  the parents were asked about how large of an improvement they noticed in their children's anxiety symptoms after the end of treatment. Nineteen out of 20 parents answered the question, which was rated on  an  11-point  scale  from  0  to  100%.  All  parents expected  at  least  some  change  in  their  children's anxiety  symptoms.  Thirteen  (68.4%)  expected  that their children's anxiety symptoms would improve by 50% or more.

TABLE 2. Diagnoses and Clinical Severity Ratings before treatment, after treatment, and at 3-Month Follow-up

|   Patient ID No. | Diagnoses Before Treatment (CSR)   | Diagnoses After Treatment (CSR)   | Diagnoses at 3-Month Follow-up (CSR)   |
|------------------|------------------------------------|-----------------------------------|----------------------------------------|
|                1 | SP darkness (6)                    | SP darkness (5)                   | SP darkness (3)                        |
|                2 | SP darkness (7)                    | SP darkness (6)                   | -                                      |
|                  | GAD (7)                            | GAD (4)                           | GAD (4)                                |
|                  | SAD (6)                            | SAD (6)                           | SAD (4)                                |
|                  | SoP (4)                            | SoP (3)                           | SoP (7)                                |
|                  | SP throwing up (8)                 | SP throwing up (8)                | SP throwing up (7)                     |
|                  | SP elevators (5)                   | SP elevators (4)                  | SP elevators (2)                       |
|                  | SP flights (4)                     | SP flights (5)                    | -                                      |
|                  | SP spiders (4)                     | SP spiders (2)                    | -                                      |
|                  | SP dentists (7)                    | SP dentists (6)                   | -                                      |
|                  | SP ferry (4)                       | -                                 | -                                      |
|                3 | SP dogs (6)                        | SP dogs (7)                       | SP animals (7)                         |
|                  | GAD (7)                            | GAD (6)                           | GAD (7)                                |
|                  | SoP (4)                            | SoP (6)                           | -                                      |
|                  | SP darkness (4)                    | SP darkness (6)                   | -                                      |
|                  | SP needles (5)                     | SP needles (2)                    | -                                      |
|                  | SP blood (5)                       | SP blood (5)                      | -                                      |
|                  | SP elevators (5)                   | SP elevators (5)                  | SP elevators (6)                       |
|                  | SP dentists (4)                    | SP dentists (6)                   | SP dentists (4)                        |
|                  | SP roller coasters (4)             | SP roller coasters (1)            | -                                      |
|                4 | SP heights (4)                     | -                                 | -                                      |
|                  | SoP (5)                            | SoP (6)                           | SoP (6)                                |
|                  | GAD (7)                            | GAD (5)                           | GAD (3)                                |
|                  | SP insects (5)                     | SP insects (6)                    | SP insects (6)                         |
|                5 | SP darkness (5)                    | -                                 | -                                      |
|                  | SP loud noises (4)                 | SP loud noises (4)                | -                                      |
|                6 | SP darkness (5)                    | -                                 | -                                      |
|                7 | SP dogs (6)                        | SP dogs (4)                       | SP dogs (3)                            |
|                8 | SP being alone (7)                 | SP being alone (6)                | -                                      |
|                  | SAD (5)                            | SAD (5)                           | -                                      |
|                  | GAD (6)                            | GAD (4)                           | -                                      |
|                  | SP insects (7)                     | SP insects (2)                    | SP insects (3)                         |
|                  | SP darkness (6)                    | SP darkness (4)                   | -                                      |
|                9 | SP dogs (7)                        | SP dogs (6)                       | SP dogs (6)                            |
|                  | SP cats (6)                        | SP cats (6)                       | SP cats (6)                            |
|               10 | SP dogs (5)                        | -                                 | -                                      |

Note: CSR, Clinical Severity Rating; GAD, generalized anxiety disorder; SAD, separation anxiety disorder; SoP, social phobia; SP, specific phobia

More than half (55%) of the parents felt that their children's  anxiety  symptoms  improved  by  50%  or more.  Thus,  the  experienced  improvement  after treatment was less than the expected improvement before treatment. All parents noticed at least a small (10%)  improvement  in  their  children's  symptoms, but none of the parents felt that the symptoms had completely disappeared.

The CSR  scores decreased significantly from before to after treatment and from pretreatment to 3-month follow-up, with large effect sizes. There was no significant difference between post-treatment and 3-month  follow-up  scores,  but  the  effect  size  was moderate.  The  total  ADIS-IV-C/P  CSR  for  all diagnoses decreased significantly from before to after treatment, from pretreatment to 3-month follow-up, and from post-treatment to 3-month follow-up, with small to large effect sizes (Table 3).

After treatment, four participants (40%) were free of  the  specific  phobias  that  were  treated;  at  the  3month  follow-up,  eight  participants  (80%)  were. Furthermore,  at  both  the  post-treatment  and  3month  follow-up  evaluations reductions, in the severity  of  the  comorbid  disorders  were  found for five  (83.3%)  of  the  six  participants  with  comorbid disorders diagnosed before treatment. After treatment,  two  participants  (20%)  were  free  of  all diagnoses; at the 3-month follow-up, six participants (60%) were diagnosis-free. Table 2 shows an overview of the changes in the diagnoses over time for  the  10  participants.  The  specific  phobias  that were treated are highlighted.

The percentage of steps completed during the BAT increased significantly from before to after treatment and from pretreatment to 3-month follow-up, with large effect sizes. The difference between the posttreatment  and  3-month  follow-up  evaluations  was not  significant,  and  the  effect  size  was  small  (see Table 3).

The rating of subjective fear at the stopping point of  the  BAT  decreased  significantly  from  before  to after  treatment  and  from  pretreatment  to  3-month follow-up,  with  large  effect  sizes.  The  difference between post-treatment and 3-month follow-up was not  significant,  and  the  effect  size  was  small  (see Table 3).

TABLE 3. Pretreatment, Post-treatment and 3-Month Follow-up Primary Outcome Measures

| Outcome Measure                                      | Pre- treatment Mean (SD)   | Post- treatment Mean (SD)   | 3-Month Follow-up Mean (SD)   | t Value, Pre- treatment to Post- treatment (df)   | t Value, Pre- treatment to 3-Month Follow- up (df)   | t Value, Post- treatment to 3-Month Follow-up (df)   |   Pre- treatment to Post- treatment Effect Size |   Pre- treatment to 3-Month Follow- up Effect Size |   Post- treatment to 3-Month Follow- up Effect Size |
|------------------------------------------------------|----------------------------|-----------------------------|-------------------------------|---------------------------------------------------|------------------------------------------------------|------------------------------------------------------|-------------------------------------------------|----------------------------------------------------|-----------------------------------------------------|
| ADIS-IV-C/P CSR for the specific phobia treated with | 5.8 (1.0)                  | 3.4 (3.0)                   | 1.9 (2.7)                     | 3.5 (9)**                                         | 4.9 (9)***                                           | 1.9 (9)                                              |                                             1.1 |                                                1.9 |                                                 0.5 |
| Total ADIS- IV-C/P CSR for all                       | 19.6 (18.3)                | 15.1 (16.7)                 | 8.4 (9.7)                     | 3.6 (9)**                                         | 3.1 (9)*                                             | 2.4 (9)*                                             |                                             0.3 |                                                0.8 |                                                 0.5 |
| Percentage of BAT steps completed                    | 42.6 (31.3)                | 69.5 (36.5)                 | 80.0 (32.8)                   | -3.1 (9)*                                         | -3.8 (9)**                                           | -2.1 (9)                                             |                                             0.8 |                                                1.2 |                                                 0.3 |
| Subjective fear as measured by the FT at the         | 6.6 (1.0)                  | 2.6 (2.2)                   | 2.3 (1.9)                     | 4.7 (8)**                                         | 5.3 (8)***                                           | 1.0 (8)                                              |                                             2.3 |                                                2.8 |                                                 0.2 |
| FSSC-R score                                         | 144.9 (31.2)               | 129.8 (31.1)                | 120.4 (32.8)                  | 3.6 (9)**                                         | 5.5 (9)****                                          | 3.5 (9)**                                            |                                             0.5 |                                                0.8 |                                                 0.3 |
| SEQ-C score                                          | 79.6 (11.3)                | 83.7 (17.0)                 | 86.1 (17.8)                   | -1.1 (9)                                          | -2.1 (9)                                             | -0.7 (9)                                             |                                             0.3 |                                                0.4 |                                                 0.1 |

* p < .05; ** p < .01; *** p ≤ .001; ****p < .001

ADIS-IV-C/P, Anxiety Disorder Interview Schedule for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition , Child and Parent versions; BAT, Behavioral Approach Test; CSR, Clinical Severity Rating; DF, differential; FSSC-R, Fear Survey Schedule for Children, Revised; FT, Fear Thermometer; OST, onesession treatment; SD, standard deviation; SEQ-C, Self-Efficacy Questionnaire for Children

Twenty-eight  (93.3%)  of  the  youths  and  their parents  found  that  the  treatment  had  helped  the youths, at least partly; only one parent and one youth did  not  find  the  treatment  helpful.  Twenty-nine (96.7%)  of  the  youths  and  their  parents  would recommend  the  treatment  to  others  with  similar problems. Only one parent would not recommend the  treatment.  Except  for  one  youth,  one  mother, and  one  father  from  different  families,  all  families answered  'not  true'  to  the  following  statement: 'The  treatment  was  causing  me/my  child  to  feel worse.' The parents were also given an open-ended question: 'Was there something that you didn't like or that can be improved?' Only eight (40%) of the parents answered the question. Half of the responses were concerns about the shortness of the treatment. One parent  suggested  that  the  treatment  could  be improved by adding another exposure session.

Twelve (60%) of the parents answered the question, 'What was good about the treatment?' Two answers in particular appeared most often: that they felt that they were in safe hands with the therapists (n = 5) and that they found the development and implementation of the fear hierarchy to be helpful (n = 4).

The FSSC-R scores decreased significantly with all three  comparisons:  before  to  after  treatment,  with moderate  effect  sizes;  pretreatment  to  3-month follow-up, with large effect sizes; and post-treatment to  3-month  follow-up,  with  small  effect  sizes  (see Table 2).

No  significant  differences  in  self-efficacy  were found between the three time points. The effect size from post-treatment to 3-month follow-up was less than  small,  the  effect  size  from  before  to  after treatment was small, and the effect size  from pretreatment  to  3-month  follow-up  was  small  to moderate (see Table 3).

Table  4  shows  the  EAT  that  the  youth  had,  on average, spent on a daily basis confronting the phobia treated during the OST according to the youth, the mother,  and  the  father.  Youths  reported  having spent an average of 20.5 minutes (SD, 23.4 minutes) per day practicing confronting their specific phobias. Mothers reported that their children spent an average of  17.0  minutes  (SD,  14.9  minutes),  and  fathers reported  an  average  of  13.0  minutes  (SD,  15.1 minutes). At 3-month follow-up, the total ADIS-IVC/P CSRs after treatment and the EATs reported by the youths, the  mothers,  and  the  fathers  were significant with regard to their prediction of the total ADIS-IV-C/P  CSRs:  the  more  time  that  a  youth spent practicing, the lower the total ADIS-IV-C/P CSR.  Table  5  shows  the  results  of  the  multiple regression analyses at 3-month follow-up.

TABLE 4. Daily Number of Minutes Spent Confronting the Specific Phobia Between the Post-treatment and 3-Month Follow-up Evaluations

|   Patient ID No. |   Youth's Report | Mother's Report   |   Father's Report |
|------------------|------------------|-------------------|-------------------|
|                1 |                5 | 5                 |                10 |
|                2 |               40 | 30                |                10 |
|                3 |               60 | 30                |                30 |
|                4 |                5 | 5                 |                 5 |
|                5 |               10 | 10                |                 5 |
|                6 |               10 | 10*               |                 5 |
|                7 |                5 | 15                |                 5 |
|                8 |               60 | 50                |                50 |
|                9 |                5 | 10                |                 5 |
|               10 |                5 | 5                 |                 5 |

*This number was adjusted; see the Statistical Analysis section of the text

TABLE 5. Summary of Multiple Regression Analyses of Total Clinical Severity Ratings of Anxiety Disorder Interview Schedule for the DSM-IV, Child and Parent versions, at 3-Month Follow-up Evaluations

|      |                                      | Criterion Variables Total ADIS-IV-C/P CSR at 3-Month Follow-up (N = 10)   | Criterion Variables Total ADIS-IV-C/P CSR at 3-Month Follow-up (N = 10)   | Criterion Variables Total ADIS-IV-C/P CSR at 3-Month Follow-up (N = 10)   |
|------|--------------------------------------|---------------------------------------------------------------------------|---------------------------------------------------------------------------|---------------------------------------------------------------------------|
| Step | Predictor Variables                  | β                                                                         | Δ R 2                                                                     | p                                                                         |
| 1    | Post-treatment total ADIS-IV-C/P CSR | 1.378                                                                     | .836                                                                      | .000                                                                      |
| 2    | Youth-reported homework              | -.593                                                                     | .137                                                                      | .001                                                                      |
| 1    | Post-treatment total ADIS-IV-C/P CSR | 1.230                                                                     | .836                                                                      | .000                                                                      |
| 2    | Mother-reported homework             | -.469                                                                     | .120                                                                      | .003                                                                      |
| 1    | Post-treatment total ADIS-IV-C/P CSR | 1.118                                                                     | .836                                                                      | .000                                                                      |
| 2    | Mother-reported homework             | .386                                                                      | .108                                                                      | .008                                                                      |

Note. ADIS-IV-C/P, Anxiety Disorder Interview Schedule for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition , Child and Parent versions; CSR, Clinical Severity Rating

50% or more in their children's symptoms after the end  of  treatment.  Thus,  although  the  treatment seemed to be well accepted, the treatment satisfaction rate could have been higher. A possible reason for the moderate satisfaction score could be that the improvements of the youth observed by the parents did not correspond with the expectations of the  parents  before  the  treatment  began.  This  may also explain why  four parents stated that the treatment was too short. Had there been a satisfaction  assessment  at  the  3-month  follow-up evaluation, the scores may have been higher, because there were significant improvements in the FSSC-R scores and total ADIS-IV-C/P CSRs for all diagnoses between the post-treatment and 3-month follow-up meetings. In addition, the total number of youths who were diagnosis-free regarding the treated

## Discussion

This  pilot  study  evaluated  the  OST  program  for youths with specific phobias at the Anxiety Clinic for Children  and  Adolescents  at  Aarhus  University  in Denmark using a single group open trial design. This is the first time that the program has been evaluated in Denmark.

There were no dropouts from the treatment, and both parents and youth expressed a moderate degree of  satisfaction  with  the  treatment.  None  of  the youths or their parents reported that the treatment was causing the youth to feel worse, and nine of the youths (90%) and 19 of the parents (95%) found the treatment to be at least partly helpful. Most of the families would recommend the treatment to a friend in a similar situation. More than half of the parents (55%) expressed that they saw an improvement of phobia doubled from the post-treatment evaluation to the 3-month follow-up.

Significant  improvements were seen from before to  after  treatment  and  from  post-treatment  to  3month follow-up on all outcome measures except for self-efficacy. At the post-treatment assessment, four of  the  participants  (40%)  were  free  of  the  specific phobia  that was  treated,  and  this  number  had doubled  by  the  time  of  the  3-month  follow-up evaluation (80%).

In this study, the percentage of participants who were free of the specific phobia after treatment was below the average of 54% that was found in a review of  the  current  status  of  OST  (11).  One  possible reason for this may be that the therapists in this study had  no  prior  experience  with  the  use  of  the  OST manual. Only two other studies have examined the number  of  youths  who  were  diagnosis-free  of  the specific  phobia  at  follow-up  after  treatment  with OST.  Ollendick  and  colleagues  (38)  found  that 67.4%  of  youth  were  diagnosis  free  at  6-month follow-up; in a previous study, Ollendick and colleagues (21) had found that 49% of youth were diagnosis-free at that time point. As compared with the results of these two studies, the current study had better 3-month follow-up results. The addition of a booster session  may have positively influenced the results of the present study.

One possible mediator of the improvement seen from the time of the post-treatment evaluation to the 3-month follow-up may be the amount of time spent confronting  the  specific  phobia  after  the  end  of treatment.  This hypothesis  is  supported  by  the results: the amount of homework completed between  the  post-treatment  meeting  and  the  3month follow-up appointment significantly predicted the total ADIS-IV-C/P CSR at follow-up after  controlling  for  the  total  ADIS-IV-C/P  CSR after treatment. It is difficult to compare this finding with other studies that have investigated the effect of homework. Although the current study only has one retrospective  measure  of  homework,  other  studies have investigated the effect of homework in longer treatment  programs,  where  homework  has  often been rated on a weekly basis. It is possible that our measure was more biased than would be the case if the homework had been rated on a weekly basis.

No  other studies that have investigated the effectiveness of OST have examined the influence of homework  on  the  outcome  variables,  so  it  is  not possible  to  compare  the  results  of  this  study  with other studies of OST.

The results of this study are in line with the results of  the  meta-analysis  by  Kazantzis  and  colleagues (15),  which  found  that  treatments  of  adults  that included homework assignments yielded significantly better  results  than  treatments  without  homework.

Because the results of using homework assignments when treating youths with anxiety are mixed (16-18), more studies are needed to investigate this association further.

Although  the  treatment  described  in  the  current study only focused on the targeted specific phobia, the severity of the comorbid disorders was reduced after  treatment  and  at  3-month  follow-up.  These findings  are  in  line  with  those  of  earlier  studies (12,13),  which  have  demonstrated  that  OST  also reduces the severity of non-targeted comorbid disorders. Participants may be able to generalize the skills  acquired  from  this  time-limited  treatment  to other situations.  Ost  and  colleagues  (12)  suggested that the increase in self-efficacy that is usually found after OST (39) helps participants to deal with their problems in more constructive ways, which leads to improvements  in  their  symptoms.  However,  no increase in self-efficacy over time as measured by the SEQ-C was found in the present study. During the exposure  portion  of  the  treatment,  many  of  the youths were observed verbalizing statements such as 'I can already feel a difference. Yesterday I wouldn't dare to have done what I just did' and 'I did not believe that I was able to do it so fast.' When leaning her body over a fifth-floor railing, one of the youths with  a  specific  phobia  of  heights  exclaimed,  'It's crazy, I don't think I ever have been so high up. I can easily live in an apartment on the sixth floor.' The responders seemed to be proud of their accomplishments, and these feelings may be generalizable  and  help  them  to  deal  with  other comorbid conditions after successful treatment. This effect on untreated comorbid disorders is noteworthy, because standard treatment for generalized anxiety disorder, separation anxiety disorder, and other similar conditions typically requires 10 to 16 CBT sessions (13).

Although  the  follow-up  results  were  promising, two  of  the  participants  (20%)  were  still  suffering from  the  treated  specific  phobia.  The  two  nonresponders had very different characteristics before entering  treatment.  One  of  them  had  only  one comorbid disorder, whereas the other had six additional specific phobias and two other comorbid conditions.  Because  low  motivation  is  associated with low treatment response, this could have been a predictor of non-response. The two non-responders had scores of 20 and 26 for the shortened version of the Nijmegen Motivation List. The average motivation score was 22.5, with a standard deviation of  3.1.  The  score  of  20  is  within  one  standard deviation below the mean, and the score of 26 is just above one standard deviation from the mean. Therefore, their motivation does not seem to be a factor that can explain the non-response. The nonresponder group did not appear to have any characteristics  that  differed  from  the  responding group, except for the fact  that  the  non-responders were  among the  youngest participants.  It  could  be interesting  for  a  future  study  with  a  bigger  sample size to investigate whether age predicts non-response to OST.

Because the two non-responders had no differentiating  characteristics,  the  reason  for  nonresponsiveness may be associated with the treatment. This could be an issue if the functional assessment did not reveal the relevant cognitions associated with the  specific  phobia  or  if  the  most  relevant  phobic stimulus was not used in the treatment. It has been suggested  that  it  may  sometimes  be  necessary  to administer  a  second  or  a  third  session  of  OST  to produce  a  better  treatment  outcome  (9).  Future studies  should  investigate  when  the  addition  of another treatment session improves treatment outcomes, especially among non-responding youths.

## Limitations of the study

The  results  of  this  study  should  be  viewed  with caution  due  to  the  most  important  limitations:  the small sample size and the lack of randomization to a control group, which limited the internal validity of the  study.  Future  studies  should  investigate  the effectiveness  of  OST  as  compared  with  active  and passive control groups in Denmark, and they should include larger sample sizes. Another limitation is the lack of a comparison group treated with the standard OST procedure without the addition of the booster session.

In  addition,  the  same  two  individuals  served  as assessors, therapists, and researchers. Although the results of the post-treatment and 3-month follow-up assessments were discussed with an external assessor, the results may be biased. The therapists did not have prior  experience  using  the  OST  manual,  and  the therapists' adherence to the manual was not assessed.

## Conclusion

On the basis of the results of this small single group pilot study, it can be tentatively concluded that OST may be useful  for  the  treatment  of  Danish  youths with specific phobias. Significant improvements in all primary  outcome  measures  appeared  between  the pretreatment to 3-month follow-up assessments. In addition  to  the  changes  in  the  targeted  specific phobias, significant improvements were also observed in the participants' non-targeted comorbid anxiety disorders. Patient self-efficacy did not increase significantly after the end of treatment. The families  were  at  least  moderately  satisfied  with  the treatment, and there were no patients who dropped out of treatment.

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