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Research Article                                                                                                                                        Open Access

## Early-Onset Schizophrenia: Exploring the Contribution of the Thought Disorder Index to Clinical Assessment

Dorte Bundgaard Andersen 1* , Ditte Lammers Vernal 2 , Niels Bilenberg 3 , Mette Skovgaard Væver 4 , Anne Dorte Stenstrøm 3

1 Child and Adolescent Psychiatric Clinic, Glostrup, Denmark 2 Research Unit for Child and Adolescent Psychiatry, Aalborg University Hospital, Denmark 3 Research Unit for Child and Adolescent Psychiatry, Child and Adolescent Psychiatric University Clinic, Odense, Denmark 4 Department of Psychology, University of Copenhagen, Denmark

*Corresponding author: dorte.bundgaard.andersen@regionh.dk

## Abstract

Background: Differentiating diagnostically between schizophrenia and emotional and personality disorders with psychotic or psychotic-like symptoms is a challenging task. It is especially difficult when working with adolescent patients, because their symptoms  tend  to  manifest  at  lower  levels  as  compared  with  adult  patients.  Thought  disorder  is  a  core  symptom  of schizophrenia, and the Rorschach Inkblot Method is widely used for the assessment of formal thought disorder.

Objective: In  this  study, which is situated within ongoing clinical practice, we investigated whether the Rorschach test is helpful for assessing early-onset schizophrenia due to its ability to detect thought disorder. We also wanted to examine whether the Thought Disorder Index (TDI) is superior to the Comprehensive System (CS) for differentiating between patients with early-onset schizophrenia and non-psychotic patients experiencing auditory and visual hallucinations. An additional aim was to examine whether the TDI correlated with the Positive and Negative Syndrome Scale (PANSS).

Methods: Twenty-three subjects between the ages of 12 and 18 years were examined with the use of the Rorschach test, and the protocols were scored according to both the TDI and the CS. All subjects were also assessed with the Positive and Negative Syndrome  Scale.  The  sample  included  14  subjects  who  fulfilled  the  criteria  for  schizophrenia  and  9  subjects  who  were experiencing hallucinations that emanated from severe emotional and relational problems but who had different non-psychotic disorders.

Results: Although the two groups could not be distinguished with regard to their total scores for thought disorder, the identification of specific thought disorder types proved useful for differential diagnosis. Verbalizations that were categorized by the TDI as 'absurd responses,' 'fluidity,' 'contamination,' 'autistic logic,' and 'word-finding difficulty' were only given by patients who had been diagnosed with schizophrenia. When patients' responses were scored with the use of the CS, the 'contamination' score was the only one found to be specific to schizophrenia.

Conclusions: Although the sample size limits the conclusions that can be drawn, the results indicate that the TDI may be superior  to  the  CS  for  the  identification  of  thought  disorder  specific  to-but  not  always  present  in-adolescents  with schizophrenia.  In  other  words,  the  absence  of  severe  thought  disorder  is  not  synonymous  with  the  absence  of  severe psychopathology,  but  the  presence  of  the  most  severe  thought  disorder  types  (i.e.,  'absurd  responses,'  'fluidity,' 'incoherence,' 'contamination,' and 'autistic logic') seems to be a strong indicator of schizophrenic psychopathology.

Keywords: Early onset schizophrenia; thought disorders; Rorschach; TDI

## Introduction

Schizophrenia is an invalidating psychiatric disorder, and early detection and treatment are crucial to an affected patient's prognosis (1). However, the assessment of early-onset schizophrenia is a challenging and time-consuming task, which is why assessment  instruments  that  are  characterized  by high sensitivity and specificity to schizophrenia symptoms are such important tools for the diagnostic process (2).

Schizophrenia in children and adolescents is usually associated with an insidious onset and with premorbid social, motor, and language impairments (3).  A  particularly  challenging  task  is  distinguishing between psychotic experiences in children and adolescents with early-onset schizophrenia and similar experiences in patients with other psychiatric disorders. Differential diagnosis with regard to schizophrenia and borderline personality disorder is particularly difficult due to the frequency of psychotic  or  psychotic-like  symptoms  in  patients with  borderline  personality  disorder  when  they  are under stress (4).

Rating scales like the Present State Examination (5) and  the  Positive  and  Negative  Syndrome  Scale (PANSS)  (6)  are  currently  regarded  as  the  gold standard for the assessment of psychotic symptoms in  children  with  schizophrenia.  These  diagnostic interviews focus on patient descriptions of subjective phenomena like delusions and hallucinations. However,  they  are  not  designed  to  elicit  formal thought disorder, which may often go unnoticed due to the structured dialogue offered by the interviews. Thought disorder is regarded as an endophenotypic marker  of  schizophrenia  as  a  result  of  Bleuler's identification  of  the  'loosening  of  associations'  in these patients, and it is considered a core symptom of  schizophrenia  (7,8).  The  use  of  the  Rorschach Inkblot Method (9) often reveals thought disorder: the patient is required to organize the unstructured stimuli of the inkblots and to verbalize what he or she  sees  to  the  clinician,  thereby  explicating  the characteristics of his or her perception and thinking. Formal thought disorder can be observed objectively by the clinician, whereas symptoms such as hallucinations must be self-reported (8).

## Assessment of thought disorder using the Rorschach approach

The  Comprehensive  System  (CS)  (9)  is  the  most commonly  used  Rorschach  approach.  A  recent international study found that approximately 96% of clinicians administer, score, and interpret the Rorschach tests using the CS (10). The special scores of the CS consist of four major categories of thought disorder  that  are  scored  on  two  levels  of  severity (Table 1) and then converted into a weighted sum of all special scores (WgtSum6). Exner's special scores are based on the work of Rapaport, who through the introduction of a nuanced system of thought disorder categories made thought disorder scoring a central  aspect  of  the  Rorschach  test  (11).  Exner picked  and  synthesized  the  most  reliable  and  valid variables from existing Rorschach systems and created an evidence based comprehensive Rorschach scoring system. The virtue of Exner's scoring system is its simplicity (11,12).

TABLE 1. Comprehensive System (CS): Special scores and severity levels

| Special score                                                                                                            |   Severity level |
|--------------------------------------------------------------------------------------------------------------------------|------------------|
| Deviant verbalization Incongruous combination Deviant response Fabulized combination                                     |                1 |
| Deviant verbalization Incongruous combination Deviant response Fabulized combination ALOG (autistic logic) Contamination |                2 |

The  WgtdSum6 is calculated by using this formula: Weighted Sum6 = (1)xDV + (2)xDV2 + (2)xINCOM + (4)xINCOM2 + (3)xDR + (6)xDR2 +(4)xFABCOM + (7)xFABCOM2 + (5)xALOG + (7)xCONTAM

However,  simplicity  may  come  at  the  expense  of sensitivity. According to Kleiger, Exner either condensed or left out discrete types of pathological verbalizations  of  particular  diagnostic  significance (12). In the clinic, Rorschach testing involving the CS often fails to distinguish between  the  different qualitative aspects of disordered thinking in patients with schizophrenia and other conditions (e.g., borderline  pathology).  Another  and  more  nuanced approach  to  scoring  thought  disorder  that  is  also based on Rapaport's work is the Thought Disorder Index (TDI) (12). The TDI comprises 23 different categories  of  thought  disorder  that  are  classified according to four levels of severity (0.25, 0.50, 0.75 and 1.0). The TDI is calculated on the basis of the total amount of thought disorder (Table 2).

The TDI has proved useful for identifying subtle differences in thought disorder and for differentiating between different types of psychosis (13,14).  Originally,  the  TDI  was  developed  as  a research instrument. With  its  larger  number  of categories  of  thought  disorder,  learning  to  use  the TDI  is  more  difficult,  and  it  is  more  difficult  to achieve  high  inter-rater  reliability.  This  may  be  the reason  that  the  TDI  has  made  few  inroads  into clinical assessment practice.

## Validity of the TDI  for assessing thought disorder during childhood and adolescence

Arboleda  and  Holzman  (15)  studied  children  with psychotic  disorders,  at-risk  children,  children  with behavioral  disorders,  and  normal  control  children. (The group with psychotic disorders was very heterogenic, however.) Significantly higher TDI

TABLE 2. Thought Disorder Index (TDI): Thought disorder categories and severity level

| Severity levels             | 0.25                                                                                                                                                                                        | 0.50                                                                                                                     | 0.75                                                    | 1.0                                   |
|-----------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------|---------------------------------------|
| Thought disorder categories | Inappropriate distance Flippancy Vagueness Peculiar verbalizations Word-finding difficulty Clangs Perseveration Incongruous combinations Relationship verbalization Idiosyncratic symbolism | Queer responses Confusion Looseness Fabulized combinations, (impossible or bizarre) Playful confabulations Fragmentation | Fluidity Absurd responses Confabulations Autistic logic | Contaminations Incoherence Neologisms |

The total TDI is calculated by using this formula:

TDI = ( ∑ [0.25 (A) + 0.50 (B) + 0.75 (C) + 1.0 (D)]  x 100 ) / Total R

A = number of responses at the 0.25 level

B = number of responses at the 0.50 level

C = number of responses at the 0.75 level

D = number of responses at the 1.0 level

R = total number of Rorschach responses

scores were reported in the children with psychotic disorders and the at-risk children. The control group had total TDI scores that ranged from 5.34 to 9.30, whereas the psychotic and at-risk groups often had TDI total scores of more than 16. Furthermore, they had more pathological responses at severity levels of 0.75 or 1.0 that involved categories such as 'fluidity,' 'confabulation,' 'autistic logic,' 'incoherence,' and 'neologisms.'

With the use of the TDI, Makowski and colleagues (16) examined whether thought disorder in patients with early-onset schizophrenia is similar to that seen in  patients  with  adult-onset  schizophrenia.  Their sample comprised 95 adolescents between the ages of 12 and 18 years. They compared 20 patients who had  been  diagnosed  with  schizophrenia  with  46 psychiatric patients with major depression (with and without  psychotic  features)  and  29  patients  with non-life-threatening somatic illnesses. The researchers found elevated levels of thought disorder in all patients with psychiatric illnesses. The patients in the schizophrenic group had the largest amount of thought disorder, and the qualitative features of the disordered  thinking  observed  in  adolescents  with schizophrenia  were  distinct  from  the  disordered thinking  seen  in  the  adolescents  with  psychotic depression. The types of thought disorder found in the  schizophrenic  group resembled those found in adults with schizophrenia and were characterized by 'idiosyncratic word usage, illogical reasoning, perceptual confusion, loss of realistic attunement to the  task,  and  loosely  related  ideas'  (16).  In  the schizophrenic group, 12 patients received antipsychotic  medication  and  had  lower  total  TDI scores than the unmedicated part of the group (16). This is in line with the dampening  effect on schizophrenic  thought  disorder  found  by  Spohn when he compared a group  of  adult  patients  with schizophrenia whose  medication had been discontinued with a group of patients with schizophrenia  who  were  still  receiving  medication (17). Antipsychotic medication reduced the manifestation  of  more  severe  thought  disturbance but had little effect on milder thought disorder (17). Twenty-five percent of the patients in the schizophrenic group did not have responses at the 0.50  level,  and  45%  did  not  have  responses  at  the 0.75 level. Thus, some of the patients with schizophrenia  only  had  minimal  thought  disorder. However, it is not clear to what extent medication accounted for those results.

Nielsen (18) used the TDI to analyze the prevalence of formal thought disorder in first-time hospitalized psychiatric patients between the ages of 18  and  38  years.  The  sample  consisted  of  146 patients: 48 patients were diagnosed with schizophrenia,  48  were  diagnosed  with  schizotypal disorder, and 50 had other diagnoses (12 of which were borderline personality disorder).  Due  to their rare  occurrence,  the  following  thought  disorder categories were excluded: 'flippancy,' 'word-finding difficulty,' 'clangs,' 'confusion,' 'looseness,' 'playful confabulation,' 'fragmentation,' 'fluidity,' 'contamination,' 'incoherence,' and 'neologisms.' The  remaining  scores were collapsed into two categories according to severity: 'idiosyncratic speech' and 'autistic logic.' Nielsen found that the 12 patients who had been diagnosed with borderline personality disorder had overall TDI scores of 17.38 and levels of severe thought disorder of 11.0; these results  were  similar  to  those  of  the  schizophrenic group, which had scores of 16.8 and 8.1, respectively (18).

Another  study  also  suggested  that  schizophrenia and borderline personality disorder cannot be distinguished on the basis of the overall amount of thought disorder (19). By comparing 51 patients with borderline personality disorder and 30 patients with schizophrenic  disorder,  Edell  found  that  the  two groups  did  not  differ  significantly  with  regard  to overall TDI scores and were thus indistinguishable on that measure (19). The mean TDI score for the schizophrenic  group  was  17.9  (range,  0.0  to  83.8), whereas  the  mean  TDI  score  for  the  borderline group  was  12.3  (range,  1.5  to  78.0).  However,  the most disorganized responses (1.0 level) were largely restricted  to  the  schizophrenic  group  (19).  The 'contamination' category was only chosen for five patients  with  schizophrenia  and  for  1  patient  with mixed borderline and schizotypal characteristics.

The TDI is considered a valid and reliable coding system for the assessment of formal thought disorder, and its use has yielded significant contributions to the clinical assessment and diagnosis of early-onset schizophrenia. Groups of patients on the  schizophrenia  spectrum  have  more  thought disorder overall in addition to thought disorder that falls into specific categories. To our knowledge, the TDI has never been used to assess thought disorder in  a  Danish  child  and  adolescent  sample,  which makes this study the first to do so. The present study has the overall aim of exploring how the use of the Rorschach  approach-and  the  coding  of  thought disorder using the TDI and the CS in particularmay contribute  to  the  clinical  assessment  of  earlyonset schizophrenia. We  also aim to examine whether  the  TDI  is  superior  to  the  CS  for  the identification of formal thought disorder. Specifically, we will test the following hypotheses:

- 1) Patients who fulfill the criteria for a diagnosis of schizophrenia will a) have higher total amounts of thought disorder; b) have more severe thought disorder; and c) have specific types of thought disorder (e.g., 'fluidity,' 'confabulation,' 'autistic logic,' 'incoherence,' 'contamination,' 'neologisms').
- 2) Patients' TDI scores will correlate with their PANSS scores.

## Methods

## Subjects

The  sample  was  comprised  of  23  adolescents  (9 males,  14  females)  between  the  ages  of  12  and  18 years (mean, 16.4 years). Fourteen patients met ICD10 criteria for schizophrenia (8 males, 6 females). Of the nine remaining patients (1 male, 8 females), five had been diagnosed with other childhood emotional disorders  (F93.8),  two  had  unspecified  behavioral and emotional disorders with onset usually occurring during childhood and adolescence (F98.9), one had mixed  personality  disorder  (F61.0),  and  one  had anxious (avoidant) personality disorder (F60.6). Subjects were recruited from the Region of Southern Denmark  at  the  Child  and  Adolescent  Psychiatric University Clinic in Odense from 2012 to 2014. All subjects were  referred  to the clinic  because  of psychotic or psychotic-like symptoms, such as visual and  auditory  hallucinations  and  paranoid  ideation. Patients  with  mental  retardation  (i.e.,  intelligence quotient <70) and patients with drug-related psychosis,  organic  psychosis,  or  neuropsychiatric disorders were excluded from the study.

When  referred  for  assessment,  five  of  the  14 patients from the schizophrenia group and six of the nine patients from the mixed group were prescribed antipsychotic medication. The majority of the patients  had  been  seen  by  psychiatrists  in  other psychiatric units in the Region of Southern Denmark before  their  referral  to  the  University  Clinic  in Odense.

## Procedures

The diagnoses followed the criteria of the International  Statistical  Classification  of  Diseases and  Related  Health  Problems,  10th  Revision,  and they were made  by an experienced child and adolescent  psychiatrist  (AS).  The  diagnoses  were based on the admission clinical interviews with the patients and their parents and on clinical interviews that  involved  the  PANSS  (6).  All  23  patients  were tested with the Rorschach test, which formed part of the  standard  assessment  routine.  The  study  was situated  within  the  ongoing  clinical  practice  of  the University  Clinic.  Thus,  for  cases  in  which  the differential  diagnoses  were  particularly  challenging, the CS formed part of the diagnostic assessment. The Rorschach test was part of the diagnostic assessment of seven patients from the schizophrenia group and six patients from the mixed group.

Patients  who  had  not  been  assessed  cognitively before their referral were tested with the Wechsler Intelligence Scale for Children, Fourth Edition (20), or  the  Wechsler  Adult  Intelligence  Scale,  Fourth Edition (21), depending on their ages. The mean total intelligence quotient was 90 (range, 74 to 109) in the schizophrenic group and 88.2 (range, 82 to 98) in the mixed group.

Thought  disorder  was  assessed  with  the  use  of both the CS and the TDI. The Rorschach tests were administered  and  transcribed  verbatim  by  the  first author (DBA), who also did the initial interpretation according to the CS and the TDI. The 23 Rorschach protocols were further interpreted according to the CS by a senior colleague and according to the TDI by one of the co-authors (DLV), who  is an experienced child psychologist; both were blinded to the  diagnostic  status  of  the  patients.  The  ratings made  by  the  raters,  who  had  been  blinded  to  the patients'  diagnoses,  were  used  in  the  final  analysis. DBA and DLV were trained and supervised in the use of the TDI on five TDI protocols not included in the study by one of the co-authors (MV), who is an experienced child psychologist. Inter-rater reliability (R = 0.9076) was calculated for five of the project protocols.

## Measures

The PANSS is a rating scale that measures positive and negative psychotic symptoms and general psychopathology. It consists of three scales: a positive scale, a negative scale, and a general psychopathology scale. Inter-rater reliability is reported to range between  0.83  and  0.87,  and criterion-related  validity  is  reported  to  be  0.77  as compared with similar rating scales (6).

The TDI is reported to have inter-rater reliability that ranges from 0.74 to 0.93 across studies (13). The validity of the instrument is described earlier in this article.

TABLE 3. Descriptive statistics

| Total N=23                   | Schizophrenia group 1 (N=14)   | Schizophrenia group 1 (N=14)   | Mixed group 2 (N=9)   | Mixed group 2 (N=9)   | p -value   |
|------------------------------|--------------------------------|--------------------------------|-----------------------|-----------------------|------------|
| Male gender - number (%)     | 8 (57.1)                       | -                              | 1 (11.1)              | -                     | p=0.04     |
| Age (mean ± SD, range)       | 16.3 ± 1.7                     | 12-18                          | 16.0 ± 1.1            | 15-18                 | Ns         |
| IQ 3 (mean ± SD, range)      | 90 ± 10.8                      | 74-109                         | 88 ± 6.4              | 80-98                 | Ns         |
| PANSS (mean ± SD, range)     | 73.3 ± 18.5                    | 40-101                         | 43.7 ± 6.3            | 36-53                 | p <.001    |
| TDI_score (mean ± SD, range) | 31.1 ± 26.8                    | 3-96.4                         | 18.8 ± 13.8           | 5.4-41.7              | Ns         |
| WgtSum6 (mean ± SD, range)   | 35.6 ± 30.9                    | 3-109                          | 14.1 ± 8.3            | 2-33                  | p =0.062   |

The CS has been demonstrated to have inter-rater reliability  that  ranges  between  0.82  and  0.97  (22). Severe thought disturbance (Critical Special Scores, Severe) are significantly related to bipolar disorder, high risk for psychosis, and psychosis (r = 0.35) (10).

## Statistics

The  following  statistical  tests  were  used:  the  chisquared test (Fisher's exact test), independent sample T-tests (parametric), and the Mann-Whitney U-test (non-parametric) as per data type and distribution for the descriptive analyses of demographic data and for the comparison of the outcomes of the two groups. Pearson's  correlation  coefficient  (r)  was  used  for correlation tests. A P value of .05 was considered to be statistically significant. All analyses were conducted  with  the  use  of  SPSS  software  version 21.0.

TABLE 4. Correlations

|           |                                       | PANSS1   | PANSS2   | PANSS3   | TDI_score   | PTI_score   | WgtSum6   |
|-----------|---------------------------------------|----------|----------|----------|-------------|-------------|-----------|
| PANSS1    | Pearson Correlation Sig. (2-tailed) N |          |          |          |             |             |           |
| PANSS2    | Pearson Correlation                   | .804**   |          |          |             |             |           |
| PANSS2    | Sig. (2-tailed)                       | .000     |          |          |             |             |           |
| PANSS2    | N                                     | 23       |          |          |             |             |           |
| PANSS3    | Pearson Correlation                   | .726**   | .848**   |          |             |             |           |
| PANSS3    | Sig. (2-tailed)                       | .000     | .000     |          |             |             |           |
| PANSS3    | N                                     | 23       | 23       |          |             |             |           |
| TDI_score | Pearson Correlation                   | .267     | .286     | .330     |             |             |           |
| TDI_score | Sig. (2-tailed)                       | .218     | .186     | .124     |             |             |           |
| TDI_score | N                                     | 23       | 23       | 23       |             |             |           |
| PTI_score | Pearson Correlation                   | .238     | -.005    | .211     | .589**      |             |           |
| PTI_score | Sig. (2-tailed)                       | .275     | .981     | .334     | .003        |             |           |
| PTI_score | N                                     | 23       | 23       | 23       | 23          |             |           |
| WgtSum6   | Pearson Correlation                   | .335     | .351     | .536**   | .804**      | .633**      |           |
| WgtSum6   | Sig. (2-tailed)                       | .118     | .100     | .008     | .000        | .001        |           |
| WgtSum6   | N                                     | 23       | 23       | 23       | 23          | 23          |           |

Note. ** Correlation is significant at the 0.01 level (2-tailed)

WgtSum6=Weighted sum for six special scores, TDI=Thought Disorder Index, PANSS=Positive and Negative Syndrome Scale, PANSS1= Positive syndrome scale, PANSS2= Negative Syndrome scale, PANSS3= General psychopathology scale

the schizophrenic group had no pathological responses, which means that no significant differences were found between the groups for these overall  measures.  This  seems  to  be  a  result  of  the small  sample  size  and  thus  a  problem  of  power. However, specific types of severe thought disorder were restricted to the schizophrenic group: verbalizations that were categorized by the TDI as 'absurd responses,' 'fluidity,' 'incoherence,' 'contamination,' and 'autistic logic' were only given by patients in this group.

In addition, the milder thought disorder represented  by  'word-finding  difficulty'  was  only seen in the patients from the schizophrenic group. One patient from the mixed group gave responses that were scored as 'confabulation' and 'neologism.' When the responses were scored using Exner's special scores, 'contamination' was the only special score found to be specific to the group with schizophrenia.

## Results

The  two  groups  did  not  differ  significantly  with regard  to  age  or  intelligence  level,  but  the  mixed group had a large majority of girls, whereas the group with schizophrenia was 57.1% boys; this represented significantly different gender proportions in the two groups per Fisher's exact test ( p = .04). The total TDI scores did not discriminate between the schizophrenic group and the mixed group (schizophrenia group, 31.1± 26.8; mixed group, 18.8 ± 13.8; p = .31). The WgtSum6 was also not able to discriminate between the groups (schizophrenia group, 35.6 ± 30.9; mixed group, 14.1 ± 8.3; p = .062) (Table 3).

The  total  amount  of  thought  disorder  measured with  the  CS  correlated  with  the  PANSS  general psychopathology score, whereas the total TDI score did not. There were no other correlations between the PANSS measures and the WgtSum6 or the TDI. The measure of the total amount of thought disorder as  measured  by  Exner's  CS  system,  the  WgtSum6, and the total TDI score were all correlated (Table 4).

Most  pathological  responses  (0.75  and  1.0)  were largely  restricted  to  being  given  by  patients  with schizophrenia (Table 5). However, six patients from

TABLE 5. TDI level 0.75 and 1.0 scores

|                                              |   Schizophrenia Group 1 |   Mixed Group 2 |
|----------------------------------------------|-------------------------|-----------------|
| ≥ 1 level 0.75 in TDI                        |                       7 |               1 |
| ≥ 1 level 1.0 in TDI                         |                       3 |               1 |
| No level 0.75 or 1.0 in TDI p- value = 0.098 |                       6 |               8 |

Note. 1 The schizophrenia group = Schizophrenia (F20.x)

2 The mixed group 0 93.8: Childhood emotional disorder 8n=5); 98.9: Unspecified behavioural and emotional disorders (n=2); 61.0 and 60.6: Personality disorders (n=2)

## Discussion

We  expected  that  the  use  of  the  Rorschach  test would  prove  helpful  for  the  clinical  assessment  of early-onset schizophrenia, and we expected that the TDI system would be superior for the identification of more types of thought disorder as compared with the CS. More specifically, we predicted that patients who had been diagnosed with schizophrenia would have a higher total amount of thought disorder and more  severe  thought  disorder  as  compared  with patients from  the  mixed  group.  Moreover,  we expected that specific types of severe thought disorder  (e.g.,  'fluidity,'  'confabulation,'  'autistic logic,' 'incoherence,' 'contamination,' 'neologisms') would be evident in patients with schizophrenia  but  not  in  patients  from  the  mixed group.  We  found  that  patients  with  schizophrenia had higher total amounts  of  thought disorder; however, the difference between the groups was not significant. The most severe types of thought disorder identified by the TDI (i.e., 'absurd responses,'  'fluidity,'  'incoherence,'  'contamination,' and 'autistic logic') were specific to patients with schizophrenia, which is in line with results from similar studies. A correlation between the TDI and the  PANSS positive  syndrome  scale  was  expected, because the PANSS includes conceptual disorganization  (among  6  other  items).  However, such a correlation was not found. One explanation could be that delusions, grandiosity, and hostilitywhich are included in the PANSS positive scale-are rarely seen in patients with early-onset schizophrenia, although they are often found in patients in whom the  illness  has  been  present  for  several  years  or  in whom it had a later age of onset.

In the group of patients with schizophrenia, five of the patients received antipsychotic medication; two of them still gave pathological responses, but none of the  medicated  patients  with  schizophrenia  were among the 6 patients with the highest overall TDI scores. According to Spohn, antipsychotic medication  has  a  dampening  effect  on  thought disorder (17).  However,  two  patients  from  the schizophrenic group who were plagued by psychotic symptoms  and  who  received  high  scores  on  the PANSS  displayed almost no thought disorder, despite not being medicated. This could be explained by the fact that not all schizophrenic patients have thought disorder, not even during the acute phase of the disease (8,23). Andreasen's research on thought disorder  offers  an  alternative  explanation  (24,25). Andreasen differentiates formal thought disorder by distinguishing between positive and negative thought disorder. Positive  thought  disorder  is  characterized by 'incoherence, derailment, tangentiality, or illogicality,' and negative thought disorder is characterized by 'poverty of speech and poverty of content' (25). Negative thought disorder is understood to be state-independent and is considered an endophenotypic marker of schizophrenia (26); it is predictive of a more invalidating  course  of  illness  (27).  The  CS  and  the TDI focus mainly on positive thought disorder and thus fail to identify negative thought disorder. However, it  seems  important  to  also  take  negative thought  disorder  into  account  during  the  clinical assessment.

## Limitations

The  small  sample  size  of  this  study  limits  the interpretation of results. The fact that the Rorschach tests were part of the assessment is another limitation of this study. However, only the CS scores were used during the diagnostic process. This could result in an association between Rorschach scoring and diagnosis that is artificially high due to the a priori assumption that severe thought disorder is specific to schizophrenia.

## Conclusion

The total amount of thought disorder was highest in the group of patients with schizophrenia. In contrast with  the  TDI,  the  WgtSum6  correlated  with  the PANSS, but neither the WgtSum6 nor the TDI was able to discriminate between  the schizophrenic group and the mixed group.  The most detailed and nuanced  assessment  of  thought  disorder  can  be found  when  using  the  TDI  system.  Word-finding difficulties  and  the  most  severe  levels  of  thoughtdisordered  responses  (0.75  and  1.0)  were  largely restricted  to-but  not  always  shown  by-patients with schizophrenia. In other words, the absence of severe thought  disorder  does not rule out the possibility that a patient has schizophrenia, but the presence of the most severe thought disorder categories (i.e., 'absurd responses,' 'fluidity,' 'incoherence,' 'contamination,' and 'autistic logic') seems to be a strong indicator of schizophrenic psychopathology. The strength of the TDI is its ability to detect these qualitative nuances of thought disorder, so we therefore argue that the TDI is superior to the CS when using the Rorschach test for the clinical assessment of early-onset schizophrenia.  Our  findings  suggest  that  specific types of thought disorder may  be specific to schizophrenia.  If  these  findings  are  replicated  by larger studies, there are implications for other assessments and for the subtyping of schizophrenia. In  addition,  such  findings  may  help  to  define  the underlying mechanisms of the disorder itself.

To  draw  more  definitive  conclusions  about  the individual strengths and limitations of the CS and the TDI for the assessment of schizophrenia and of a possible  combination  of  these  scoring  systems,  a much larger study is necessary.

## Ethics

The data presented in this article were collected as part of the standard clinical assessment of patients at the  Child  and  Adolescent  Psychiatric  University Clinic in Odense. Data have been anonymized, and there are no  ethical issues associated with  this project. The project has been reported to the Danish Data Protection Agency. No ethical research committee  approval  was  needed,  because  the  data were obtained during the course of standard clinical care.

## References

1. Ruhrmann S, Schultze-Lutter F, Klosterkotter J. Intervention in the at-risk state to prevent transition to psychosis. Curr Opin Psychiatry 2009;22(2):177-83.
2. Asarnow JR, Tompson MC, McGrath EP. Annotation: childhoodonset schizophrenia: clinical and treatment issues. J Child Psychol Psychiatry 2004;45(2):180-94.
3. Jacobsen  LK,  Rapoport  JL.  Research  update:  childhood-onset schizophrenia: implications of clinical and neurobiological research. J Child Psychol Psychiatry 1998;39(1):101-13.
4. Dammann G. Differential diagnosis between borderline personality disorder  and  schizophrenic  illness  in  adolescents  with  psychotic symptoms. In: Bürgin D, Meng H, (Eds.). Childhood and adolescent psychosis. Basel: Karger; 2004. p. 94-108.
5. Wing JK, Birley JL, Cooper JE, Graham P, Isaacs AD. Reliability of a  procedure  for  measuring  and  classifying  'present  psychiatric state'. Br J Psychiatry 1967;113(498):499-515.
6. Kay SR, Fiszbein A, Opler LA. The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophr Bull 1987;13(2):261-76.
7. Gooding DC, Coleman MJ, Roberts SA, et al. Thought disorder in offspring  of  schizophrenic  parents:  findings  from  the  New  York High-Risk Project. Schizophr Bull 2012;38(2):263-71.
8. Roche  E,  Creed  L,  MacMahon  D,  Brennan  D,  Clarke  M.  The epidemiology  and  associated  phenomenology  of  formal  thought disorder: A systematic review. Schizophr Bull 2015;41(4):951-62.
9. Exner JE. The Rorschach: A comprehensive system, volume 1, basic foundations  and  principles  of  interpretation.  4 th   ed.  New  York: Wiley; 2002.
10. Mihura JL, Meyer GJ, Dumitrascu N, Bombel G. The validity of individual Rorschach variables: systematic reviews and  metaanalyses of the comprehensive system. Psychol Bull 2013;139(3):548-605.
11. Kleiger JH. Disordered thinking and the Rorschach. London: The Analytic Press; 1999.
12. Kleiger  JH.  Disordered  thinking.  In:  Weiner  IB,  Craighead  WE, (Eds.) The Corsini Encyclopedia of Psychology. 4 th  ed. Hoboken, NJ: John Wiley & Sons, Inc; 2010.
13. Holzman PS, Levy DL, Johnston MH. The Use of the Rorschach technique for assessing formal thought disorder. In: Bornstein RF & Masling JM (Eds.). Scoring the Rorschach: Seven Validated Systems. Mahwah, NJ: Lawrence Erlbaum Associates; 2005.
14. Acklin M. The Rorschach test and forensic psychological evaluation: Psychosis  and  the  insanity  defense.  In:  Gacono  CB,  Evans  FB (Eds.).  The  Handbook  of  Forensic  Rorschach  Assessment.  New York: Taylor & Francis; 2008, p. 157-74.
15. Arboleda C, Holzman PS. Thought disorder in children at risk for psychosis. Arch Gen Psychiatry 1985;42(10):1004-13.
16. Makowski D, Waternaux C, Lajonchere CM, et al. Thought disorder in  adolescent-onset  schizophrenia.  Schizophr  Res  1997;23(2):14765.
17. Spohn  HE,  Coyne  L,  Larson  J,  Mittleman  F,  Spray  J,  Hayes  K. Episodic and residual thought pathology in chronic schizophrenics: effect of neuroleptics. Schizophr Bull 1986;12(3):394-407.
18. Nielsen J. [Tanker og det der kommer imellem. Ph.d.-afhandling om formelle tankeforstyrrelser og identifikation af skizofrenispektrum forstyrrelser].  Det  Sundhedsvidenskabelige  Fakultet,  Københavns Universitet; 2002.
19. Edell WS. Role of structure in disordered thinking in borderline and schizophrenic disorders. J Pers Assess 1987;51(1):23-41.
20. Wechsler D. Wechsler intelligence scale for children-Fourth Edition (WISC-IV). San Antonio, TX: The Psychological Corporation; 2003.
21. Wechsler D. Wechsler adult intelligence scale, 4 th  ed (WAIS-IV). San Antonio, TX: NCS Pearson; 2008.
22. Meyer  GJ,  Hilsenroth  MJ,  Baxter  D,  et  al.  An  examination  of interrater  reliability  for  scoring  the  Rorschach  Comprehensive System in eight data sets. J Pers Assess 2002;78(2):219-74.
23. Harrow M, Marengo JT. Schizophrenic thought disorder at followup: its persistence and prognostic significance. Schizophr Bull 1986;12(3):373-93.
24. Andreasen  NC,  Olsen  S. Negative v positive schizophrenia. Definition and validation. Arch Gen Psychiatry 1982;39(7):789-94.
25. Andreasen NC, Grove WM. Thought, language, and communication in schizophrenia: diagnosis and prognosis. Schizophr Bull 1986;12(3):348-59.
26. Gooding DC, Ott SL, Roberts SA, Erlenmeyer-Kimling L. Thought disorder  in  mid-childhood  as  a  predictor  of  adulthood  diagnostic outcome: findings from the New York High-Risk Project. Psychol Med 2013;43(5):1003-12.
27. Wilcox  J,  Winokur  G,  Tsuang  M.  Predictive  value  of  thought disorder in new-onset psychosis. Compr Psychiatry 2012;53(6):6748.