# Dutch Translation and Validation of the3b2:?thyc=10Headache-Specific3b2:?thyc Locus of Control Scale (HSLC-DV)

Authors: Marceline C. Willekens; Don Postel; Martin D. M. Keesenberg; Robert Lindeboom
Journal: Pain Research and Management
 (2018)

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## Abstract

Background and Objective. The assessment of locus of control forms an important part of headache treatment, and there is need to adapting them to the Dutch population. Methods. 3b2:?thyc=10Forward-backward3b2:?thyc translation was used to obtain the 3b2:?thyc=10Headache-Specific3b2:?thyc Locus of Control Scale–3b2:?show $132#Dutch Version (3b2:?thyc=10HSLC-DV).3b2:?thyc The response of 87 participants with migraine, 3b2:?thyc=10tension-type3b2:?thyc headache, and cervicogenic headache, aged between 18 and 55 years (75% female), is used. 3b2:?thyc=10Test-retest3b2:?thyc reliability was measured by intraclass correlations. Construct validity was assessed by correlations with corresponding domains of the Pain Coping and Cognition List (PCCL) and by confirmation of known groups hypotheses. Structural validity was evaluated by factor analysis (principal axis factoring). Results. The intraclass correlations for the External, Internal, and Chance domains were 0.79, 0.89, and 0.73, respectively. Internal consistencies for domains exceeded 0.73 and were similar to those observed in the original study. Convergent correlations were as expected and three of the seven known groups hypotheses were confirmed. Structural validity was supported by results of the factor analysis that matched the proposed structure of the original instrument. Conclusions. The 3b2:?thyc=10HSLC-DV3b2:?thyc is a valid and reliable questionnaire for measuring the locus of control.


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## Body

## 1. Introduction

3b2:?A3B2 tlsb .1pt
3b2:?A3B2 tpt 1ptMigraine and 3b2:?thyc=10tension-type3b2:?thyc headaches are highly prevalent and have a strong impact on society [1,[tnq_nbsp] 2]. Locus of Control (LoC) is related to the impact of headaches and chronic pain [3]. The extent patients believe they can control events affecting their pain is influenced by the degree of LoC [4,[tnq_nbsp] 5]. Individuals with internal LoC believe that events in their life derive primarily from their own actions. Individuals with External LoC attribute outcomes of events to external circumstances, for example, “the intervention of powerful others such as 3b2:?thyc=10health-care3b2:?thyc professionals.” Chance LoC represents unordered forces such as fate and luck [6]. 3b2:?thyc=10Cognitive-behavioral3b2:?thyc therapy (CBT) is a successful and most common psychological approach in treating pain and is effective in reducing disability and catastrophic reaction [2]. Positive outcomes have been detected also in patients with chronic daily headaches [2]. CBT helps to reduce pain by learning how to manage the LoC in headaches [2].3b2:?A3B2 tlsb .1ptInfluencing the level of LoC of patients with headache leads to faster and more sustained recovery from headaches [7]. The patient empowerment proceeds from the perspective that optimal outcomes of an intervention are achieved when patients become active participants in their treatment process [3,[tnq_nbsp] 7].3b2:?A3B2 tlsb -.15ptThe 3b2:?thyc=10Headache-Specific3b2:?thyc Locus of Control Scale (HSLC) by Martin en Holroyd [4] was developed in the US using the framework from Rotter’s social learning theory [8]. The original US English version [4] of the HSLC showed promising psychometric properties. 3b2:?thyc=10Three-week3b2:?thyc 3b2:?thyc=10test-retest3b2:?thyc reliabilities of the subscales ranged between 0.72 and 0.78. Internal consistency reliabilities ranged between 0.84 and 0.88 [6]. Danish [5] and Spanish [9] versions are available. The Danish version was reliable and valid in a multiethnic sample from a tertiary care headache center.To assess LoC in Dutch patients with headache, the Pain Coping and Cognition List (PCCL) is used. However, the PCCL includes two domains measuring more global internal and external pain management and was not specifically developed for patients with headache.3b2:?thyc=10Headache-specific3b2:?thyc instruments can be useful to screen patients on their Internal or External LoC before the treatment as it may affect the outcome [7]. We argue that there is a need for a specific instrument to measure LoC in patients with headache in Dutch. We developed a Dutch version of the HSLC (3b2:?thyc=10HSLC-DV).3b2:?thyc The aim of the present study is to investigate the reliability and validity of the HSLC-DV.


## 2. Methods

### 2.1. Translation Procedure

3b2:?A3B2 tlsb -.1ptAfter obtaining permission from the developer (Professor Kenneth Holroyd, Ohio University), the original HSLC questionnaire was translated by a translation agency. Two translators independently translated the original US English version of the HSLC into Dutch. A third independent translator merged these two Dutch HSLC versions into the best suitable Dutch translation for each item. Subsequently, this Dutch version of the HSLC was backward translated into English by two other independent translators of the translation agency. These independent translators were unacquainted with the original US English version of the 3b2:?A3B2 tlsb -.13ptHSLC. Another independent translator translated again forward into Dutch.3b2:?A3B2 tlsb -0.15ptA focus group consisting of four content experts with regard to the target group achieved consensus on comprehensibility and translation. Subsequently, 20 3b2:?thyc=10health-care3b2:?thyc professionals (10 psychologists and 10 general practitioners) evaluated the equivalence between the original and the translated version of the HSLC. After this assessment, the final Dutch version was composed, the 3b2:?thyc=10HSLC-DV3b2:?thyc (Appendix).


### 2.2. Participants

3b2:?A3B2 tlsb .1ptEligible participants were patients with[tnq_nbsp] a history of headaches visiting two referral centers (“Corpus Mentis, Center for Physical Therapy & Science” or “het Wantveld”) for treatment. Additionally, patients were recruited through the websites of the Dutch Association for Physical Therapy & Science (part of Corpus Mentis) and two patient support groups of the Dutch Migraine Association. The participants of the support groups were already diagnosed with migraine by visiting a physician in the past. Migraine patients were not recruited in the referral centers because they are not visiting a physiotherapist for their headache problems on a regular basis. Patients with migraine [4], cervicogenic headache [9], and 3b2:?thyc=10tension-type3b2:?thyc headache [4], between the ages of 18 and 55 years old with headache complaints lasting longer than two months, were included. 3b2:?thyc=10Thirty-five3b2:?thyc patients were allocated to the migraine 3b2:?A3B2 tlsb -0.19ptgroup and 52 to the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group. All participants were native Dutch speakers and signed informed consent after receiving information about the purpose and procedure of the research. Exclusion criteria were stroke, TIA, CVA, dementia, 3b2:?thyc=10pregnancy/menopause, 3b2:?thycmedication overuse or cluster headache, tumors, and use of alcohol or special medication.


### 2.3. Assessment Instruments and Procedure

The participants included from Wantveld and Corpus Mentis were diagnosed by the physical therapist through history taking and physical examination, and after inclusion they filled out the survey. Patients completed the survey after inclusion (T0) and after[tnq_nbsp] 3b2:?A3B2 tlsb -.1ptthree weeks (T1). The survey included the 3b2:?thyc=10HSLC-DV3b2:?thyc (Appendix), the Pain Coping and Cognition List (PCCL [10]), and the numeric pain rating scale (NPRS [11]).The HSLC [3] is a 3b2:?thyc=10self-report3b2:?thyc questionnaire and contains 33 items with a Likert response scale ranging from 1 (strongly disagree) to 5 (strongly agree). The questionnaire has three subscales consisting of 11 items each: Internal LoC, External LoC, and Chance LoC. Each subscale score may range from 11 to 55 points. Lower scores reflect lower levels of the trait being measured by a subscale [12].The PCCL [10] has 42 items and measures dealing with pain, LoC, and pain cognitions, within four subscales: Pain Coping (11 items), Catastrophizing (12 items), Internal Pain Management (11 items), and External Pain Management (8 items). It uses a 6-point Likert scale: 1 (totally disagree) to 6 (totally agree). The total scores and subscale scores may range from 1 to 6 points (total score divided by number of questions that were answered).The NPRS [11] was used as a global measure of the experienced pain intensity and runs from 0 (no pain) to 10 (the worst pain you can imagine). The patient was instructed to circle the number that reflects the severity of the pain in the past week.A Global Rating of Change (GRC) was included at T1 to inquire to what extent the headache complaints were changed at3b2:?thyc=10follow-up.3b2:?thyc A score of −5 indicates much worsened symptoms compared to the previous measurement, 0 indicates unchanged, and +5 indicates a maximum improvement compared to the previous measurement.Patients were recruited from May 2014 to February 2015. Questions on demographic and clinical characteristics were included in the T0 survey. Patients provided3b2:?thyc=10self-reported3b2:?thyc information including headache intensity, headache episodes and headache duration, age and gender as well as work status, children, doctors’ visits, sport, education level, civil status, and medication use (Table[tnq_nbsp] 3b2:?show [?"tbl1",5,"cond1"]1).Table 1
Baseline characteristics.
Total sample (N=87)
Lost[tnq_nbsp] to[tnq_nbsp] follow-3b2:?show $132#up (N=16)
3b2:?show "^tbl_width"$01649v
Gender
Male
21 (24%)
3 (19%)
Mean (SD) age in years
36 (9)
35 (7)
Headache type
Migraine
35 (40%)
5 (31%)
Tension type and cervicogenic headache
52 (60%)
11 (69%)
Median (range) headache days per month
8 (1–3b2:?show $132#31)
8 (4–3b2:?show $132#30)
Median duration of headache in years
13 (1–3b2:?show $132#45)
13 (3–3b2:?show $132#30)
Median duration of headache period in days
3 (0.5–3b2:?show $132#31)
2 (0.5–3b2:?show $132#6)
Headache treatment
34 (39%)
4 (25%)
Work
Full-time
40 (46%)
7 (44%)
Part-time
32 (37%)
7 (44%)
No paid work
11 (13%)
1 (6%)
Freelance
4 (4%)
1 (6%)
Median (range) number of children
0 (0–3b2:?show $132#6)
1 (0–3b2:?show $132#3)
Sports or moderate physical activity for 30[tnq_nbsp] min a day1
No sports or moderate physical activity
26 (30%)
9 (56%)
Moderate physical activity only
32 (37%)
4 (25%)
>2x a week sport
29 (33%)
3 (19%)
Education2
Low
44 (51%)
8 (50%)
High
43 (49%)
8 (50%)
Civil status
Single
18 (21%)
2 (13%)
Relation, living with partner, (re)married
65 (75%)
13 (81%)
Divorced
4 (5%)
1 (6%)
Medication
Pain medication
63 (72%)
13 (81%)
Beta-blocker
2 (2%)
0 (0%)
Blood pressure-lowering drugs
3 (3%)
0 (0%)
Doctors visit in median times a year
2 (0–3b2:?show $132#25)
2 (0–3b2:?show $132#6)
HSLC
External
24.2 (6.9)
23.4 (5.2)
Internal
34.9 (9.3)
37.8 (9.5)
Chance
33.8 (7.0)
35.0 (5.3)
Numbers are frequencies (%), mean (SD), or median (range).1Dutch norm for healthy exercise. 2High education = higher vocational education and science education.The survey was provided on paper and as an online version. Participants who did not respond to the request to fill out the questionnaires received a reminder by3b2:?thyc=10e-3b2:?show $132#mail3b2:?thyc after 10 days. After two reminders, patients were excluded from the analysis.


### 2.4. Reliability

Reproducibility of the3b2:?thyc=10HSLC-DV3b2:?thyc domain scores was assessed by comparing the scores on T0 and T1 using intraclass correlations (ICCs), (consistency model, single measures). The reproducibility of the item scores was investigated using weighted kappas. Weighted kappas were estimated by calculating ICCs [13]. Random and systematic measurement error of the 3b2:?thyc=10HSLC-DV3b2:?thyc was evaluated through the method of Bland & Altman that examines the magnitude of the mean score differences between T0 and T1 and by calculating limits of agreement (LoA) [14]. LoA were calculated as the mean sumscore differences between T0 and T1 ±1.96 × the standard deviation of the differences. LoA were calculated for the total sample and for the subsample with GRC scores between −1 and +1 who were considered unchanged in their headache severity at 3b2:?thyc=10follow-up.3b2:?thyc Internal consistency was evaluated by Cronbach’s alpha and 3b2:?thyc=10item-rest3b2:?thyc correlations. Cronbach’s alpha values for the subscales were compared to those of the original US version [4] study and with the Danish version [5]. 3b2:?thyc=10Item-rest3b2:?thyc correlations of >0.30 were considered as adequate [15].3b2:?A3B2 tpb -2pt


### 2.5. Construct Validity

Validity of the Dutch HSLC was evaluated by the correlations of3b2:?thyc=10HSLC-DV3b2:?thyc domains with corresponding domains of the PCCL. We regarded correlations between 0.1 and 0.3 as low, between 0.3 and 0.5 as medium, and between 0.5 and 0.7 as high [16]. We expected a 3b2:?thyc=10medium/high 3b2:?thyccorrelation (r>0.40) between the domains Internal LoC and External LoC of the 3b2:?thyc=10HSLC-DV3b2:?thyc and PCCL and between the 3b2:?thyc=10HSLC-DV3b2:?thyc Chance LoC and PCCL Catastrophizing (convergent correlations) [4,[tnq_nbsp] 9]. We expected low correlations between dissimilar domains of both instruments (divergent correlations). In addition, we also tested mean score differences between subgroups based on the following hypotheses (“known groups” validation):(1)
3b2:?A3B2 tlsb -.15ptWe expected lower Internal LoC scores for the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group compared to the 3b2:?thyc=10Migraine-Type3b2:?thyc group. 3b2:?thyc=10Tension-type3b2:?thyc headache and cervicogenic headache are more often the results of stress and burnout complaints that are in turn associated with lower Internal LoC scores [17,[tnq_nbsp] 18].(2)
We expected higher Internal scores for higher educated people compared to lower educated people. According to Pellino and Oberst, a higher educational level may indicate that the individual has more3b2:?thyc=10problem-solving3b2:?thyc ability or a higher level of 3b2:?thyc=10self-efficacy3b2:?thyc in dealing with chronic pain [19].(3)
We expected higher Internal LoC scores for men compared to woman. Men were found to be more inclined to believe that headache problems and headache relief are determined by their own actions or behaviors [19–3b2:?show $132#21].(4)
We expected higher Internal LoC scores for subjects who actively practiced sports or engaged daily in at least 30 minutes of moderate physical activity compared to those who did not. The positive influence of sports activity on the production of endorphins reduces the stress hormone cortisol [22]. Previous studies found that subjects who actively practice sports have higher scores on the Internal LoC than others [18].(5)
We expected higher External LoC scores for subjects under (medical) headache treatment compared to3b2:?thyc=10no-headache3b2:?thyc treatment. Higher levels of medication use and preference for medical treatment were associated with External LoC in the original US study and the Spanish validation [4,[tnq_nbsp] 9].(6)
We expected higher Chance LoC scores with more frequent headache days per month [4].(7)
We expected higher Chance LoC scores with longer duration in days of headache episodes [4].


### 2.6. Structural Validity

Structural validity of the3b2:?thyc=10HSLC-DV3b2:?thyc was examined by a principal axis factoring analysis with orthogonal (Varimax) rotation in order to test the purported subscale structure of the 3b2:?thyc=10HSLC-DV.3b2:?thyc A forced 3b2:?thyc=10three-factor3b2:?thyc structure was used. Factor loadings > 0.40 for individual 3b2:?A3B2 tlsb -.15ptitems were considered indicative of subscale domain membership. Kaiser–3b2:?show $132#Meyer–3b2:?show $132#Olkin test was used to examine whether the data are suited for factor analysis. KMO test values may range between 0 and 1. Values below 0.50 are deemed unacceptable. KMO measure of sampling adequacy was 0.69 indicating that the sample was large enough to conduct[tnq_nbsp] a principal component analysis.


### 2.7. Statistical Analysis

Numerical data were presented as mean (SD) or median (range) as appropriate. Differences between clinical subgroups were assessed with independentt-test or a 3b2:?thyc=10one-way3b2:?thyc ANOVA in case of >2 groups or[tnq_nbsp] a nonparametric variant when assumptions of equal variances and normality were not met. All hypotheses were tested 3b2:?thyc=10two-sided.3b2:?thyc In our analyses, P<0.05 signified statistical significance. Differences in baseline and 3b2:?thyc=10follow-up3b2:?thyc scores of respondents were tested with paired t-tests. Convergent and divergent (Pearson’s) correlations between the HSLC and subscales of the PCCL were obtained by bootstrapping based on 1000 bootstrap samples.There were no missing values on individual3b2:?thyc=10HSLC-DV3b2:?thyc items on T0. For the respondents on T1, one patient had 3 missing items, two had two missing items, and seven patients had one missing item. Little’s MCAR test was not significant, and missing item values were imputed by expectation-maximization.


## 2.1. Translation Procedure

3b2:?A3B2 tlsb -.1ptAfter obtaining permission from the developer (Professor Kenneth Holroyd, Ohio University), the original HSLC questionnaire was translated by a translation agency. Two translators independently translated the original US English version of the HSLC into Dutch. A third independent translator merged these two Dutch HSLC versions into the best suitable Dutch translation for each item. Subsequently, this Dutch version of the HSLC was backward translated into English by two other independent translators of the translation agency. These independent translators were unacquainted with the original US English version of the 3b2:?A3B2 tlsb -.13ptHSLC. Another independent translator translated again forward into Dutch.3b2:?A3B2 tlsb -0.15ptA focus group consisting of four content experts with regard to the target group achieved consensus on comprehensibility and translation. Subsequently, 20 3b2:?thyc=10health-care3b2:?thyc professionals (10 psychologists and 10 general practitioners) evaluated the equivalence between the original and the translated version of the HSLC. After this assessment, the final Dutch version was composed, the 3b2:?thyc=10HSLC-DV3b2:?thyc (Appendix).


## 2.2. Participants

3b2:?A3B2 tlsb .1ptEligible participants were patients with[tnq_nbsp] a history of headaches visiting two referral centers (“Corpus Mentis, Center for Physical Therapy & Science” or “het Wantveld”) for treatment. Additionally, patients were recruited through the websites of the Dutch Association for Physical Therapy & Science (part of Corpus Mentis) and two patient support groups of the Dutch Migraine Association. The participants of the support groups were already diagnosed with migraine by visiting a physician in the past. Migraine patients were not recruited in the referral centers because they are not visiting a physiotherapist for their headache problems on a regular basis. Patients with migraine [4], cervicogenic headache [9], and 3b2:?thyc=10tension-type3b2:?thyc headache [4], between the ages of 18 and 55 years old with headache complaints lasting longer than two months, were included. 3b2:?thyc=10Thirty-five3b2:?thyc patients were allocated to the migraine 3b2:?A3B2 tlsb -0.19ptgroup and 52 to the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group. All participants were native Dutch speakers and signed informed consent after receiving information about the purpose and procedure of the research. Exclusion criteria were stroke, TIA, CVA, dementia, 3b2:?thyc=10pregnancy/menopause, 3b2:?thycmedication overuse or cluster headache, tumors, and use of alcohol or special medication.


## 2.3. Assessment Instruments and Procedure

The participants included from Wantveld and Corpus Mentis were diagnosed by the physical therapist through history taking and physical examination, and after inclusion they filled out the survey. Patients completed the survey after inclusion (T0) and after[tnq_nbsp] 3b2:?A3B2 tlsb -.1ptthree weeks (T1). The survey included the 3b2:?thyc=10HSLC-DV3b2:?thyc (Appendix), the Pain Coping and Cognition List (PCCL [10]), and the numeric pain rating scale (NPRS [11]).The HSLC [3] is a 3b2:?thyc=10self-report3b2:?thyc questionnaire and contains 33 items with a Likert response scale ranging from 1 (strongly disagree) to 5 (strongly agree). The questionnaire has three subscales consisting of 11 items each: Internal LoC, External LoC, and Chance LoC. Each subscale score may range from 11 to 55 points. Lower scores reflect lower levels of the trait being measured by a subscale [12].The PCCL [10] has 42 items and measures dealing with pain, LoC, and pain cognitions, within four subscales: Pain Coping (11 items), Catastrophizing (12 items), Internal Pain Management (11 items), and External Pain Management (8 items). It uses a 6-point Likert scale: 1 (totally disagree) to 6 (totally agree). The total scores and subscale scores may range from 1 to 6 points (total score divided by number of questions that were answered).The NPRS [11] was used as a global measure of the experienced pain intensity and runs from 0 (no pain) to 10 (the worst pain you can imagine). The patient was instructed to circle the number that reflects the severity of the pain in the past week.A Global Rating of Change (GRC) was included at T1 to inquire to what extent the headache complaints were changed at3b2:?thyc=10follow-up.3b2:?thyc A score of −5 indicates much worsened symptoms compared to the previous measurement, 0 indicates unchanged, and +5 indicates a maximum improvement compared to the previous measurement.Patients were recruited from May 2014 to February 2015. Questions on demographic and clinical characteristics were included in the T0 survey. Patients provided3b2:?thyc=10self-reported3b2:?thyc information including headache intensity, headache episodes and headache duration, age and gender as well as work status, children, doctors’ visits, sport, education level, civil status, and medication use (Table[tnq_nbsp] 3b2:?show [?"tbl1",5,"cond1"]1).Table 1
Baseline characteristics.
Total sample (N=87)
Lost[tnq_nbsp] to[tnq_nbsp] follow-3b2:?show $132#up (N=16)
3b2:?show "^tbl_width"$01649v
Gender
Male
21 (24%)
3 (19%)
Mean (SD) age in years
36 (9)
35 (7)
Headache type
Migraine
35 (40%)
5 (31%)
Tension type and cervicogenic headache
52 (60%)
11 (69%)
Median (range) headache days per month
8 (1–3b2:?show $132#31)
8 (4–3b2:?show $132#30)
Median duration of headache in years
13 (1–3b2:?show $132#45)
13 (3–3b2:?show $132#30)
Median duration of headache period in days
3 (0.5–3b2:?show $132#31)
2 (0.5–3b2:?show $132#6)
Headache treatment
34 (39%)
4 (25%)
Work
Full-time
40 (46%)
7 (44%)
Part-time
32 (37%)
7 (44%)
No paid work
11 (13%)
1 (6%)
Freelance
4 (4%)
1 (6%)
Median (range) number of children
0 (0–3b2:?show $132#6)
1 (0–3b2:?show $132#3)
Sports or moderate physical activity for 30[tnq_nbsp] min a day1
No sports or moderate physical activity
26 (30%)
9 (56%)
Moderate physical activity only
32 (37%)
4 (25%)
>2x a week sport
29 (33%)
3 (19%)
Education2
Low
44 (51%)
8 (50%)
High
43 (49%)
8 (50%)
Civil status
Single
18 (21%)
2 (13%)
Relation, living with partner, (re)married
65 (75%)
13 (81%)
Divorced
4 (5%)
1 (6%)
Medication
Pain medication
63 (72%)
13 (81%)
Beta-blocker
2 (2%)
0 (0%)
Blood pressure-lowering drugs
3 (3%)
0 (0%)
Doctors visit in median times a year
2 (0–3b2:?show $132#25)
2 (0–3b2:?show $132#6)
HSLC
External
24.2 (6.9)
23.4 (5.2)
Internal
34.9 (9.3)
37.8 (9.5)
Chance
33.8 (7.0)
35.0 (5.3)
Numbers are frequencies (%), mean (SD), or median (range).1Dutch norm for healthy exercise. 2High education = higher vocational education and science education.The survey was provided on paper and as an online version. Participants who did not respond to the request to fill out the questionnaires received a reminder by3b2:?thyc=10e-3b2:?show $132#mail3b2:?thyc after 10 days. After two reminders, patients were excluded from the analysis.


## 2.4. Reliability

Reproducibility of the3b2:?thyc=10HSLC-DV3b2:?thyc domain scores was assessed by comparing the scores on T0 and T1 using intraclass correlations (ICCs), (consistency model, single measures). The reproducibility of the item scores was investigated using weighted kappas. Weighted kappas were estimated by calculating ICCs [13]. Random and systematic measurement error of the 3b2:?thyc=10HSLC-DV3b2:?thyc was evaluated through the method of Bland & Altman that examines the magnitude of the mean score differences between T0 and T1 and by calculating limits of agreement (LoA) [14]. LoA were calculated as the mean sumscore differences between T0 and T1 ±1.96 × the standard deviation of the differences. LoA were calculated for the total sample and for the subsample with GRC scores between −1 and +1 who were considered unchanged in their headache severity at 3b2:?thyc=10follow-up.3b2:?thyc Internal consistency was evaluated by Cronbach’s alpha and 3b2:?thyc=10item-rest3b2:?thyc correlations. Cronbach’s alpha values for the subscales were compared to those of the original US version [4] study and with the Danish version [5]. 3b2:?thyc=10Item-rest3b2:?thyc correlations of >0.30 were considered as adequate [15].3b2:?A3B2 tpb -2pt


## 2.5. Construct Validity

Validity of the Dutch HSLC was evaluated by the correlations of3b2:?thyc=10HSLC-DV3b2:?thyc domains with corresponding domains of the PCCL. We regarded correlations between 0.1 and 0.3 as low, between 0.3 and 0.5 as medium, and between 0.5 and 0.7 as high [16]. We expected a 3b2:?thyc=10medium/high 3b2:?thyccorrelation (r>0.40) between the domains Internal LoC and External LoC of the 3b2:?thyc=10HSLC-DV3b2:?thyc and PCCL and between the 3b2:?thyc=10HSLC-DV3b2:?thyc Chance LoC and PCCL Catastrophizing (convergent correlations) [4,[tnq_nbsp] 9]. We expected low correlations between dissimilar domains of both instruments (divergent correlations). In addition, we also tested mean score differences between subgroups based on the following hypotheses (“known groups” validation):(1)
3b2:?A3B2 tlsb -.15ptWe expected lower Internal LoC scores for the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group compared to the 3b2:?thyc=10Migraine-Type3b2:?thyc group. 3b2:?thyc=10Tension-type3b2:?thyc headache and cervicogenic headache are more often the results of stress and burnout complaints that are in turn associated with lower Internal LoC scores [17,[tnq_nbsp] 18].(2)
We expected higher Internal scores for higher educated people compared to lower educated people. According to Pellino and Oberst, a higher educational level may indicate that the individual has more3b2:?thyc=10problem-solving3b2:?thyc ability or a higher level of 3b2:?thyc=10self-efficacy3b2:?thyc in dealing with chronic pain [19].(3)
We expected higher Internal LoC scores for men compared to woman. Men were found to be more inclined to believe that headache problems and headache relief are determined by their own actions or behaviors [19–3b2:?show $132#21].(4)
We expected higher Internal LoC scores for subjects who actively practiced sports or engaged daily in at least 30 minutes of moderate physical activity compared to those who did not. The positive influence of sports activity on the production of endorphins reduces the stress hormone cortisol [22]. Previous studies found that subjects who actively practice sports have higher scores on the Internal LoC than others [18].(5)
We expected higher External LoC scores for subjects under (medical) headache treatment compared to3b2:?thyc=10no-headache3b2:?thyc treatment. Higher levels of medication use and preference for medical treatment were associated with External LoC in the original US study and the Spanish validation [4,[tnq_nbsp] 9].(6)
We expected higher Chance LoC scores with more frequent headache days per month [4].(7)
We expected higher Chance LoC scores with longer duration in days of headache episodes [4].


## 2.6. Structural Validity

Structural validity of the3b2:?thyc=10HSLC-DV3b2:?thyc was examined by a principal axis factoring analysis with orthogonal (Varimax) rotation in order to test the purported subscale structure of the 3b2:?thyc=10HSLC-DV.3b2:?thyc A forced 3b2:?thyc=10three-factor3b2:?thyc structure was used. Factor loadings > 0.40 for individual 3b2:?A3B2 tlsb -.15ptitems were considered indicative of subscale domain membership. Kaiser–3b2:?show $132#Meyer–3b2:?show $132#Olkin test was used to examine whether the data are suited for factor analysis. KMO test values may range between 0 and 1. Values below 0.50 are deemed unacceptable. KMO measure of sampling adequacy was 0.69 indicating that the sample was large enough to conduct[tnq_nbsp] a principal component analysis.


## 2.7. Statistical Analysis

Numerical data were presented as mean (SD) or median (range) as appropriate. Differences between clinical subgroups were assessed with independentt-test or a 3b2:?thyc=10one-way3b2:?thyc ANOVA in case of >2 groups or[tnq_nbsp] a nonparametric variant when assumptions of equal variances and normality were not met. All hypotheses were tested 3b2:?thyc=10two-sided.3b2:?thyc In our analyses, P<0.05 signified statistical significance. Differences in baseline and 3b2:?thyc=10follow-up3b2:?thyc scores of respondents were tested with paired t-tests. Convergent and divergent (Pearson’s) correlations between the HSLC and subscales of the PCCL were obtained by bootstrapping based on 1000 bootstrap samples.There were no missing values on individual3b2:?thyc=10HSLC-DV3b2:?thyc items on T0. For the respondents on T1, one patient had 3 missing items, two had two missing items, and seven patients had one missing item. Little’s MCAR test was not significant, and missing item values were imputed by expectation-maximization.


## 3. Results

A total of 87 patients with headache completed the survey at T0, and 16 patients did not return or completed the survey after three weeks at T1 (Figure[tnq_nbsp] 3b2:?show [?"gr1",5,"cond1"]1). The baseline characteristics of the 16 patients that were lost to 3b2:?thyc=10follow-up3b2:?thyc were not notably different. Baseline LoC subscale scores of the total sample were approximately normally distributed and were comparable to those of the patients who did not complete the study (Table[tnq_nbsp] 1). The online version was completed by 81 patients and six completed the paper version at T0. At T1, 6 3b2:?A3B2 tlsb -.1ptpatients completed the paper version and 65 patients completed the online version. The participants were outpatients from the referral centers (52 patients) or patient the support groups (35 patients).Figure 1
Flowchart.


### 3.1. Reliability of the HSLC-DV

The reproducibility and internal consistency results are summarized in Table[tnq_nbsp] 3b2:?show [?"tbl2",5,"cond1"]2. Cronbach’s alpha ranged from 0.73 for Chance LoC to 0.89 for Internal LoC. These results are in line with the Danish study and the original US study. All 3b2:?thyc=10item-rest3b2:?thyc correlations exceeded 0.30 except for two items of the External subscale and two items of the Chance subscale. Weighted kappas, as estimated using ICCs, for the items of the External LoC, Internal LoC, and Chance LoC ranged from 0.24 to 0.77 (median 0.58), 0.21 to 0.70 (median 0.59), and 0.43 to 0.68 (median 0.60), respectively.Table 2
Reproducibility and internal consistency of the HSLC-DV (N=87).
Weighted kappa
Item-rest correlation
Cronbach’s alpha if item deleted
Cronbach’s alpha
3b2:?show "^tbl_width"$01649v
External LoC
0.79 (0.75∗) (0.88∗∗)
HSLC6
0.24
0.12
0.80
HSLC8
0.43
0.47
0.77
HSLC10
0.44
0.56
0.76
HSLC12
0.34
0.28
0.79
HSLC14
0.61
0.54
0.76
HSLC15
0.34
0.26
0.79
HSLC16
0.69
0.55
0.76
HSLC22
0.69
0.51
0.76
HSLC24
0.77
0.47
0.77
HSLC27
0.58
0.44
0.77
HSLC30
0.62
0.61
0.75
Internal LoC
0.89 (0.88∗) (0.86∗∗)
HSLC2
0.57
0.60
0.88
HSLC4
0.21
0.56
0.88
HSLC5
0.60
0.66
0.88
HSLC7
0.59
0.52
0.89
HSLC11
0.59
0.67
0.88
HSLC17
0.68
0.79
0.87
HSLC19
0.62
0.73
0.87
HSLC21
0.53
0.61
0.88
HSLC26
0.44
0.38
0.89
HSLC28
0.70
0.67
0.88
HSLC32
0.55
0.57
0.88
Chance LoC
0.73 (0.71∗) (0.84∗∗)
HSLC1
0.60
0.49
0.70
HSLC3
0.66
0.60
0.68
HSLC9
0.63
0.43
0.71
HSLC13
0.57
0.56
0.69
HSLC18
0.58
−0.02
0.77
HSLC20
0.43
0.32
0.72
HSLC23
0.60
0.53
0.70
HSLC25
0.61
0.55
0.69
HSLC29
0.68
0.06
0.76
HSLC31
0.51
0.39
0.71
HSLC33
0.56
0.36
0.72
LoC = Locus of Control subscale. Numbers correspond to the original HSLC scale.∗Danish study. ∗∗Original US study.The intraclass correlations (95%CI) for the External, Internal, and Chance domains were 0.77 (0.65–3b2:?show $132#0.85), 0.81 (0.70–3b2:?show $132#0.88), and 0.79 (0.67–3b2:?show $132#0.86), respectively.3b2:?A3B2 tlsb 0.2ptThe mean difference between the External scores on the 3b2:?thyc=10HSLC-DV3b2:?thyc between T0 and T1 was −0.42 points, and limits of agreement (LoA) were −11.2 to 10.4 points. The mean differences (LoA) for the Internal scores and the Chance scores were −0.94 (−12.1–3b2:?show $132#10.2) and 0.85 (−8.7–3b2:?show $132#10.4), 3b2:?A3B2 tlsb -0.3ptrespectively. For a subsample of the participants with GRC scores −1 to +1 (N=35), these were respectively 0.88 (−7.0–3b2:?show $132#8.8), −0.96 (−11.7–3b2:?show $132#9.8), and −0.97 (−9.0–3b2:?show $132#7.1). Intraclass correlations in the subsample were practically equal to those calculated for the total sample: 0.83 (0.68–3b2:?show $132#0.91), 0.82 (0.67–3b2:?show $132#0.91), and 0.81 (0.66–3b2:?show $132#0.90) for the External, Internal, and Chance scales, respectively.


### 3.2. Construct Validity of the HSLC-DV

Table[tnq_nbsp] 3b2:?show [?"tbl3",5,"cond1"]3 shows the correlations between 3b2:?thyc=10HSLC-DV3b2:?thyc subscale scores and PCCL subscale scores. All convergent and divergent correlations were as hypothesized except for those between the HSLC Chance and PCCL Catastrophizing that had a correlation of 0.36 (P<0.01). 3b2:?A3B2 tlsb -.17ptPearson correlations between 3b2:?thyc=10HSLC-DV3b2:?thyc subscales and PCCL pain or NPRS at T0 and T1 were generally small and not significant (r<0.20, not shown in Table[tnq_nbsp] 3).Table 3
Pearson correlations between HSLC subscales and similar domains of the PCCL (N=87).
PCCL3b2:?show $6#external
PCCL3b2:?show $6#internal
PCCL3b2:?show $6#catastrophizing
3b2:?show "^tbl_width"$01649v
HSLC external
0.64
∗
∗
0.12
0.20
HSLC internal
−0.10
0.42
∗
∗
−0.02
HSLC chance
0.27∗
−0.35∗∗
0.36
∗
∗
Convergent correlations are given in bold. HSLC = Headache-Specific Locus of Control Scale; PCCL = Pain Coping and Cognition List.∗P<0.05.∗∗P<0.01.Table[tnq_nbsp] 3b2:?show [?"tbl4",5,"cond1"]4 shows the mean scores of clinical subgroups to test the construct validity hypotheses. From the seven HSLC hypotheses, three were confirmed (headache treatment, headache frequency, and headache duration) and four hypothesis were not confirmed (headache type, education, gender, and 3b2:?thyc=10sports/moderate 3b2:?thycphysical activity). For example, contrary to what was hypothesized, there was a higher mean score on Internal LoC for the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group compared with the Migraine group. Similarly, subjects who exercised at least 30 minutes of moderate physical activity or who actively engaged in sports had lower Internal LoC scores than those who did not (33.3 versus 38.7, P=0.01). Higher educated subjects had, as hypothesized, higher Internal scores (35.13 versus 34.65), however not significant (P=0.93).Table 4
Known groups and hypotheses (N=87).
External
Internal
Chance
3b2:?show "^tbl_width"$01649v
(1)
Migraine (N=35)
24.98 (7.20)
32.88 (9.78)
33.68 (6.68)
Tension type + cervicogenic headache (N=52)
23.61 (6.65)
36.24 (8.87)
33.93 (7.25)
P
=
0.34
P
=0
.15
P
=
0.76
(2)
Education, low (N=44)
25.47 (6.87)
34.65 (9.52)
34.36 (6.90)
Education, high (N=43)
22.82 (6.67)
35.13 (9.26)
33.29 (7.12)
P
=
0.08
P
=0
.93
P
=
0.37
(3)
Male (N=21)
23.97 (6.27)
37.70 (7.04)
32.34 (8.05)
Female (N=66)
24.22 (7.09)
33.99 (9.84)
34.30 (6.61)
P
=
0.89
P
=0
.40
P
=
0.30
(4)
No sport (N=26)
23.30 (5.65)
38.71 (9.74)
32.68 (5.92)
Moderate activity + 2x wk sports (N=61)
24.53 (7.34)
33.26 (8.75)
34.32 (7.39)
0.47
P
=0
.0
1
∗
P
=
0.19
(5)
No treatment (N=53)
22.99 (6.15)
35.39 (9.97)
33.54 (6.44)
Treatment (N=34)
25.99 (7.59)
34.11 (8.36)
34.27 (7.85)
P
=0
.0
4
∗
P
=
0.45
P
=
0.43
(6)
0–3b2:?show $132#8 headache days per month (N=44)
23.73 (6.01)
35.76 (8.34)
31.22 (6.35)
9–3b2:?show $132#31 headache days per month (N=43)
24.60 (7.69)
34.00 (10.29)
36.50 (6.65)
P
=
0.54
P
=
0.92
P<
0
.00
1
∗
(7)
0–3b2:?show $132#3 days per headache period (N=58)
24.14 (6.1)
34.84 (8.89)
32.54 (6.46)
4–3b2:?show $132#31 days per headache period (N=29)
24.20 (8.30)
36.75 (9.05)
36.40 (7.40)
P
=
0.99
P
=
0.56
P
=0
.0
1
∗
P values for construct validity hypotheses are given in bold. HSLC = Headache-Specific Locus of Control Scale. Scores are mean (SD). Score differences are tested using the Mann–3b2:?show $132#Whitney U test. ∗P<0.05.


### 3.3. Structural Validity of the HSLC-DV

3b2:?A3B2 tlsb -0.1ptThe factor analysis (Table[tnq_nbsp] 3b2:?show [?"tbl5",5,"cond1"]5) largely confirmed the proposed 3b2:?thyc=10three-factor3b2:?thyc structure of the 3b2:?thyc=10HSLC-DV3b2:?thyc except for item 6 (Internal scale, low loading on all 3 factors) and items 18 (Chance item, loaded on External factor) and 29 (Chance item with low loading). The extracted factors explained 41% of the variance.Table 5
Structural validity: factor loadings on the purported subscales of the HSLC-DV scale.
Internal LoC eigenvalue = 6.8
External LoC eigenvalue = 4.3
Chance LoC eigenvalue = 2.4
3b2:?show "^tbl_width"$01649v
External LoC
HSLC6∗
0.168
0.100
0.228
HSLC8
0.190
0.512
0.229
HSLC10
0.230
0.687
−0.080
HSLC12
0.056
0.336
0.118
HSLC14
−0.108
0.643
0.153
HSLC15∗
−0.093
0.356
0.145
HSLC16
−0.112
0.720
0.028
HSLC22
0.220
0.619
−0.134
HSLC24
−0.052
0.639
0.188
HSLC27
0.030
0.534
0.037
HSLC30
0.062
0.702
0.057
Internal LoC
HSLC2
0.660
−0.013
−0.123
HSLC4
0.596
0.037
−0.157
HSLC5
0.699
0.000
−0.195
HSLC7
0.638
0.147
0.023
HSLC11
0.729
−0.012
−0.076
HSLC17
0.796
0.061
−0.216
HSLC19
0.845
0.054
0.037
HSLC21
0.600
0.084
−0.353
HSLC26
0.429
−0.067
−0.281
HSLC28
0.742
−0.041
−0.083
HSLC32
0.618
0.019
−0.201
Chance LoC
HSLC1
−0.224
−0.148
0.650
HSLC3
−0.205
−0.217
0.707
HSLC9
−0.249
0.019
0.568
HSLC13
−0.142
0.122
0.650
HSLC18∗
0.479
0.114
0.096
HSLC20
0.041
0.162
0.423
HSLC23
−0.020
0.186
0.694
HSLC25
−0.129
0.271
0.674
HSLC29∗
−0.032
−0.223
0.088
HSLC31
−0.130
0.163
0.484
HSLC33
−0.276
−0.181
0.415
Three factors explained 41% of the total variance in HSLC-DV scores.∗Cross-loadings or items that do not load (<0.40) on the purported subscale.


## 3.1. Reliability of the HSLC-DV

The reproducibility and internal consistency results are summarized in Table[tnq_nbsp] 3b2:?show [?"tbl2",5,"cond1"]2. Cronbach’s alpha ranged from 0.73 for Chance LoC to 0.89 for Internal LoC. These results are in line with the Danish study and the original US study. All 3b2:?thyc=10item-rest3b2:?thyc correlations exceeded 0.30 except for two items of the External subscale and two items of the Chance subscale. Weighted kappas, as estimated using ICCs, for the items of the External LoC, Internal LoC, and Chance LoC ranged from 0.24 to 0.77 (median 0.58), 0.21 to 0.70 (median 0.59), and 0.43 to 0.68 (median 0.60), respectively.Table 2
Reproducibility and internal consistency of the HSLC-DV (N=87).
Weighted kappa
Item-rest correlation
Cronbach’s alpha if item deleted
Cronbach’s alpha
3b2:?show "^tbl_width"$01649v
External LoC
0.79 (0.75∗) (0.88∗∗)
HSLC6
0.24
0.12
0.80
HSLC8
0.43
0.47
0.77
HSLC10
0.44
0.56
0.76
HSLC12
0.34
0.28
0.79
HSLC14
0.61
0.54
0.76
HSLC15
0.34
0.26
0.79
HSLC16
0.69
0.55
0.76
HSLC22
0.69
0.51
0.76
HSLC24
0.77
0.47
0.77
HSLC27
0.58
0.44
0.77
HSLC30
0.62
0.61
0.75
Internal LoC
0.89 (0.88∗) (0.86∗∗)
HSLC2
0.57
0.60
0.88
HSLC4
0.21
0.56
0.88
HSLC5
0.60
0.66
0.88
HSLC7
0.59
0.52
0.89
HSLC11
0.59
0.67
0.88
HSLC17
0.68
0.79
0.87
HSLC19
0.62
0.73
0.87
HSLC21
0.53
0.61
0.88
HSLC26
0.44
0.38
0.89
HSLC28
0.70
0.67
0.88
HSLC32
0.55
0.57
0.88
Chance LoC
0.73 (0.71∗) (0.84∗∗)
HSLC1
0.60
0.49
0.70
HSLC3
0.66
0.60
0.68
HSLC9
0.63
0.43
0.71
HSLC13
0.57
0.56
0.69
HSLC18
0.58
−0.02
0.77
HSLC20
0.43
0.32
0.72
HSLC23
0.60
0.53
0.70
HSLC25
0.61
0.55
0.69
HSLC29
0.68
0.06
0.76
HSLC31
0.51
0.39
0.71
HSLC33
0.56
0.36
0.72
LoC = Locus of Control subscale. Numbers correspond to the original HSLC scale.∗Danish study. ∗∗Original US study.The intraclass correlations (95%CI) for the External, Internal, and Chance domains were 0.77 (0.65–3b2:?show $132#0.85), 0.81 (0.70–3b2:?show $132#0.88), and 0.79 (0.67–3b2:?show $132#0.86), respectively.3b2:?A3B2 tlsb 0.2ptThe mean difference between the External scores on the 3b2:?thyc=10HSLC-DV3b2:?thyc between T0 and T1 was −0.42 points, and limits of agreement (LoA) were −11.2 to 10.4 points. The mean differences (LoA) for the Internal scores and the Chance scores were −0.94 (−12.1–3b2:?show $132#10.2) and 0.85 (−8.7–3b2:?show $132#10.4), 3b2:?A3B2 tlsb -0.3ptrespectively. For a subsample of the participants with GRC scores −1 to +1 (N=35), these were respectively 0.88 (−7.0–3b2:?show $132#8.8), −0.96 (−11.7–3b2:?show $132#9.8), and −0.97 (−9.0–3b2:?show $132#7.1). Intraclass correlations in the subsample were practically equal to those calculated for the total sample: 0.83 (0.68–3b2:?show $132#0.91), 0.82 (0.67–3b2:?show $132#0.91), and 0.81 (0.66–3b2:?show $132#0.90) for the External, Internal, and Chance scales, respectively.


## 3.2. Construct Validity of the HSLC-DV

Table[tnq_nbsp] 3b2:?show [?"tbl3",5,"cond1"]3 shows the correlations between 3b2:?thyc=10HSLC-DV3b2:?thyc subscale scores and PCCL subscale scores. All convergent and divergent correlations were as hypothesized except for those between the HSLC Chance and PCCL Catastrophizing that had a correlation of 0.36 (P<0.01). 3b2:?A3B2 tlsb -.17ptPearson correlations between 3b2:?thyc=10HSLC-DV3b2:?thyc subscales and PCCL pain or NPRS at T0 and T1 were generally small and not significant (r<0.20, not shown in Table[tnq_nbsp] 3).Table 3
Pearson correlations between HSLC subscales and similar domains of the PCCL (N=87).
PCCL3b2:?show $6#external
PCCL3b2:?show $6#internal
PCCL3b2:?show $6#catastrophizing
3b2:?show "^tbl_width"$01649v
HSLC external
0.64
∗
∗
0.12
0.20
HSLC internal
−0.10
0.42
∗
∗
−0.02
HSLC chance
0.27∗
−0.35∗∗
0.36
∗
∗
Convergent correlations are given in bold. HSLC = Headache-Specific Locus of Control Scale; PCCL = Pain Coping and Cognition List.∗P<0.05.∗∗P<0.01.Table[tnq_nbsp] 3b2:?show [?"tbl4",5,"cond1"]4 shows the mean scores of clinical subgroups to test the construct validity hypotheses. From the seven HSLC hypotheses, three were confirmed (headache treatment, headache frequency, and headache duration) and four hypothesis were not confirmed (headache type, education, gender, and 3b2:?thyc=10sports/moderate 3b2:?thycphysical activity). For example, contrary to what was hypothesized, there was a higher mean score on Internal LoC for the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group compared with the Migraine group. Similarly, subjects who exercised at least 30 minutes of moderate physical activity or who actively engaged in sports had lower Internal LoC scores than those who did not (33.3 versus 38.7, P=0.01). Higher educated subjects had, as hypothesized, higher Internal scores (35.13 versus 34.65), however not significant (P=0.93).Table 4
Known groups and hypotheses (N=87).
External
Internal
Chance
3b2:?show "^tbl_width"$01649v
(1)
Migraine (N=35)
24.98 (7.20)
32.88 (9.78)
33.68 (6.68)
Tension type + cervicogenic headache (N=52)
23.61 (6.65)
36.24 (8.87)
33.93 (7.25)
P
=
0.34
P
=0
.15
P
=
0.76
(2)
Education, low (N=44)
25.47 (6.87)
34.65 (9.52)
34.36 (6.90)
Education, high (N=43)
22.82 (6.67)
35.13 (9.26)
33.29 (7.12)
P
=
0.08
P
=0
.93
P
=
0.37
(3)
Male (N=21)
23.97 (6.27)
37.70 (7.04)
32.34 (8.05)
Female (N=66)
24.22 (7.09)
33.99 (9.84)
34.30 (6.61)
P
=
0.89
P
=0
.40
P
=
0.30
(4)
No sport (N=26)
23.30 (5.65)
38.71 (9.74)
32.68 (5.92)
Moderate activity + 2x wk sports (N=61)
24.53 (7.34)
33.26 (8.75)
34.32 (7.39)
0.47
P
=0
.0
1
∗
P
=
0.19
(5)
No treatment (N=53)
22.99 (6.15)
35.39 (9.97)
33.54 (6.44)
Treatment (N=34)
25.99 (7.59)
34.11 (8.36)
34.27 (7.85)
P
=0
.0
4
∗
P
=
0.45
P
=
0.43
(6)
0–3b2:?show $132#8 headache days per month (N=44)
23.73 (6.01)
35.76 (8.34)
31.22 (6.35)
9–3b2:?show $132#31 headache days per month (N=43)
24.60 (7.69)
34.00 (10.29)
36.50 (6.65)
P
=
0.54
P
=
0.92
P<
0
.00
1
∗
(7)
0–3b2:?show $132#3 days per headache period (N=58)
24.14 (6.1)
34.84 (8.89)
32.54 (6.46)
4–3b2:?show $132#31 days per headache period (N=29)
24.20 (8.30)
36.75 (9.05)
36.40 (7.40)
P
=
0.99
P
=
0.56
P
=0
.0
1
∗
P values for construct validity hypotheses are given in bold. HSLC = Headache-Specific Locus of Control Scale. Scores are mean (SD). Score differences are tested using the Mann–3b2:?show $132#Whitney U test. ∗P<0.05.


## 3.3. Structural Validity of the HSLC-DV

3b2:?A3B2 tlsb -0.1ptThe factor analysis (Table[tnq_nbsp] 3b2:?show [?"tbl5",5,"cond1"]5) largely confirmed the proposed 3b2:?thyc=10three-factor3b2:?thyc structure of the 3b2:?thyc=10HSLC-DV3b2:?thyc except for item 6 (Internal scale, low loading on all 3 factors) and items 18 (Chance item, loaded on External factor) and 29 (Chance item with low loading). The extracted factors explained 41% of the variance.Table 5
Structural validity: factor loadings on the purported subscales of the HSLC-DV scale.
Internal LoC eigenvalue = 6.8
External LoC eigenvalue = 4.3
Chance LoC eigenvalue = 2.4
3b2:?show "^tbl_width"$01649v
External LoC
HSLC6∗
0.168
0.100
0.228
HSLC8
0.190
0.512
0.229
HSLC10
0.230
0.687
−0.080
HSLC12
0.056
0.336
0.118
HSLC14
−0.108
0.643
0.153
HSLC15∗
−0.093
0.356
0.145
HSLC16
−0.112
0.720
0.028
HSLC22
0.220
0.619
−0.134
HSLC24
−0.052
0.639
0.188
HSLC27
0.030
0.534
0.037
HSLC30
0.062
0.702
0.057
Internal LoC
HSLC2
0.660
−0.013
−0.123
HSLC4
0.596
0.037
−0.157
HSLC5
0.699
0.000
−0.195
HSLC7
0.638
0.147
0.023
HSLC11
0.729
−0.012
−0.076
HSLC17
0.796
0.061
−0.216
HSLC19
0.845
0.054
0.037
HSLC21
0.600
0.084
−0.353
HSLC26
0.429
−0.067
−0.281
HSLC28
0.742
−0.041
−0.083
HSLC32
0.618
0.019
−0.201
Chance LoC
HSLC1
−0.224
−0.148
0.650
HSLC3
−0.205
−0.217
0.707
HSLC9
−0.249
0.019
0.568
HSLC13
−0.142
0.122
0.650
HSLC18∗
0.479
0.114
0.096
HSLC20
0.041
0.162
0.423
HSLC23
−0.020
0.186
0.694
HSLC25
−0.129
0.271
0.674
HSLC29∗
−0.032
−0.223
0.088
HSLC31
−0.130
0.163
0.484
HSLC33
−0.276
−0.181
0.415
Three factors explained 41% of the total variance in HSLC-DV scores.∗Cross-loadings or items that do not load (<0.40) on the purported subscale.


## 4. Discussion

We translated and validated the HSLC in a Dutch sample. The item reproducibility over a similar time interval as the original US study was generally good, except for item 4 (prevent headaches by not getting emotionally upset) and item 6 (prevent headaches by doctor). We found a comparable internal consistency as reported in the US and Danish validation studies. Most items contributed to the internal consistency although some items (items 6, 18, and 29) did not. The convergent correlations (>0.40) and divergent correlations (<0.30) between subscales of the3b2:?thyc=10HSLC-DV3b2:?thyc and related subscales of the PCCL were as expected. Only the HSLC Chance subscale correlated somewhat lower with the PCCL Catastrophizing scale (0.36). Catastrophizing in the 3b2:?A3B2 tlsb -.12ptUS study was considered as a strategy for coping with headaches when chance or fate play a primary role in the onset of headache episodes. This is similar to what is measured by the HSLC Chance scale. Structural validity of the 3b2:?thyc=10HSLC-DV3b2:?thyc was supported by the principal component analysis results. The vast majority of the items exclusively loaded on the intended subscales.We expected a difference between men and woman. Men were found to be more inclined to believe that headache problems and headache relief are determined by their own actions or behaviors. This difference was not found in our results, comparable with Cano-García et[tnq_nbsp] al. [3].3b2:?A3B2 tlsb .15ptFrom the seven HSLC known groups hypotheses, five were confirmed of which two reached no statistical significance. For example, contrary to what was expected, the mean Internal LoC score in the 3b2:?thyc=10Tension-Type3b2:?thyc and Cervicogenic Headache group was higher than that in the 3b2:?thyc=10Migraine-type3b2:?thyc group. We argue that the HSLC measures symptoms that may be present in all the three types of headaches. Hence, the hypotheses outcomes were not as expected for the different types.3b2:?A3B2 tlsb=0.05ptMigraine patients are usually comorbid to depression [2]. The comorbidity with major affective disorders is more prevalent in subjects suffering from the chronic type of migraine, hence these patients report more frequently high levels of hopelessness and suicidal risk [2]. In our study, differences between chronic migraine and migraine were not investigated. Because we focused on the validation of the questionnaire, the factor depression was not processed in the analyses nor comorbidity factors in patients with headache.No difference was observed for “sports or moderate physical activity for 30[tnq_nbsp] min a day” with lower Internal LoC scores for physically active subjects.3b2:?A3B2 tpb 1pt


### 4.1. Study Limitations

In our study, the relatively small sample size for the Principal Component Analysis is the first limitation. Further research in larger sample sizes should be completed to reach more definite conclusions regarding the structural validity of the3b2:?thyc=10HSLC-DV.3b2:?thyc A second limitation of this study is possible selection bias. A part of the sample may[tnq_nbsp] not be representative of the regular headache subjects visiting the referral centers for treatment because we also recruited patients from 3b2:?thyc=10patient-support3b2:?thyc groups. This could have led to inclusion of patients with chronic headache with longer disease duration. We argue that patients with longer sustained headaches were more willing to participate in this study, as we can see in the high median duration of headaches in years at baseline of this group. In our study, more women (75%) were included than men. We argue that this could be a representative reflection of the headache population because women are affected 2 to 4 times more often by headaches than men [23]. A third limitation is the 3b2:?A3B2 tlsb .1ptclassification of headache types based on 3b2:?thyc=10self-report.3b2:?thyc Patients of the support groups were not verified or seen by a physician and had to classify their type of headaches according to the given symptoms and definitions in the survey. The 3b2:?thyc=10patient-support3b2:?thyc groups were associated with the Dutch Migraine Association and were approached for the inclusion of migraine patients, the most prevalent headache type. These participants were assumed confirmed migraine cases. We did not rule out possible secondary headaches in the migraine group. Despite this limitation, we argue that for the validation of this questionnaire, the importance is more on headache characteristics (localization, intensity, and duration) than on the underlying mechanism. The accuracy of the diagnosis is fundamental, and we want to promote more researches that could provide reliable results.3b2:?A3B2 tlsb .3ptFinally, Nilsson and Bove have classified TTH and CH together as “musculoskeletal headache” [24]. We argue that the myogene headache group and migraine group represented a good heterogeneity for validation of the LoC questionnaire. For the validation of the HSLC, inclusion of these headache types better reflects the characteristics of the general population of patients with headache.3b2:?A3B2 tpb=8pt


## 4.1. Study Limitations

In our study, the relatively small sample size for the Principal Component Analysis is the first limitation. Further research in larger sample sizes should be completed to reach more definite conclusions regarding the structural validity of the3b2:?thyc=10HSLC-DV.3b2:?thyc A second limitation of this study is possible selection bias. A part of the sample may[tnq_nbsp] not be representative of the regular headache subjects visiting the referral centers for treatment because we also recruited patients from 3b2:?thyc=10patient-support3b2:?thyc groups. This could have led to inclusion of patients with chronic headache with longer disease duration. We argue that patients with longer sustained headaches were more willing to participate in this study, as we can see in the high median duration of headaches in years at baseline of this group. In our study, more women (75%) were included than men. We argue that this could be a representative reflection of the headache population because women are affected 2 to 4 times more often by headaches than men [23]. A third limitation is the 3b2:?A3B2 tlsb .1ptclassification of headache types based on 3b2:?thyc=10self-report.3b2:?thyc Patients of the support groups were not verified or seen by a physician and had to classify their type of headaches according to the given symptoms and definitions in the survey. The 3b2:?thyc=10patient-support3b2:?thyc groups were associated with the Dutch Migraine Association and were approached for the inclusion of migraine patients, the most prevalent headache type. These participants were assumed confirmed migraine cases. We did not rule out possible secondary headaches in the migraine group. Despite this limitation, we argue that for the validation of this questionnaire, the importance is more on headache characteristics (localization, intensity, and duration) than on the underlying mechanism. The accuracy of the diagnosis is fundamental, and we want to promote more researches that could provide reliable results.3b2:?A3B2 tlsb .3ptFinally, Nilsson and Bove have classified TTH and CH together as “musculoskeletal headache” [24]. We argue that the myogene headache group and migraine group represented a good heterogeneity for validation of the LoC questionnaire. For the validation of the HSLC, inclusion of these headache types better reflects the characteristics of the general population of patients with headache.3b2:?A3B2 tpb=8pt


## 5. Conclusions

3b2:?A3B2 tlsb 0.2ptWe conclude that the 3b2:?thyc=10HSLC-DV3b2:?thyc is a reliable and valid instrument to measure LoC in a Dutch sample of patients with headache. Therefore, we strongly recommend the use of the 3b2:?thyc=10HSLC-DV3b2:?thyc in the treatment counseling of patients with headache. Future research is necessary to determine cutoff points for the different scales of the 3b2:?thyc=10HSLC-DV3b2:?thyc to identify patients with poor outcome on the headache treatment.3b2:?A3B2 tpb 8pt



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*Source: 3046235-2018-05-02.xml*