Psychometric Properties of the Persian Version of the Weiss Functional Impairment Rating Scale

Abstract

Objective: The Weiss Functional Impairment Rating Scale–Self-Report Form (WFIRS-S) was developed as a measure of functional impairment in adolescents and adults with ADHD. This study reports the psychometric properties of the Persian version of the WFIRS-S in a sample of normal Iranian adolescents. Method: Internal consistency and factor structure of the WFIRS-S were tested on a sample of 386 students (Grades 7-12). The test-retest reliability and the convergent validity of the WFIRS-S were evaluated by using two different subsamples including 50 and 100 students, respectively. Results: The Cronbach’s alpha values were between .72 and .94 for the WFIRS-S subdomains and total scale. The test-retest reliability was .80 for the total scale. The WFIRS-S subdomains had moderate to high significant correlations with the Pediatric Quality of Life total scale. Conclusion: The Persian version of the WFIRS-S has acceptable psychometric properties and could be used as a functional impairment assessment for adolescents.

Keywords

ADHD adolescents functional impairment Weiss Functional Impairment Rating Scale–self-report form psychometric properties

Introduction

ADHD is a prevalent and well-known neurobehavioral disorder that persists into adolescence in almost 70% of the cases and into adulthood in nearly 66% of the childhood cases (Barkley, Fischer, Edelbrock, & Smallish, 1990; Barkley, Fischer, Smallish, & Fletcher, 2002; Mannuzza, Klein, Bessler, Malloy, & LaPadula, 1993; Weiss & Hechtman, 1993). Diagnostic criteria require age inappropriate symptoms in at least one of the two categories of inattention and hyperactivity-impulsivity and also substantial reduction in the quality of social, academic, or occupational functioning (American Psychiatric Association [APA], 2013). ADHD-related deficits have an extreme impact on quality of life and functioning that continues into adulthood (Das, Cherbuin, Butterworth, Anstey, & Easteal, 2012; Gjervan, Torgersen, Nordahl, & Rasmussen, 2011; Hechtman et al., 2016; Lensing, Zeiner, Sandvik, & Opjordsmoen, 2015). Based upon the diagnostic guideline and substantial functional impairment in patients with ADHD, a method for systematic evaluation of functional impairment is an essential part of the ADHD assessment. There are several important reasons to assess the functional impairment such as determining the severity of the problem, checking the need for treatment, designing an appropriate plan for treatment, identifying treatment goals, measuring the usefulness of treatment, and predicting future function of the patient (Algorta, Dodd, Stringaris, & Youngstrom, 2016; Haack & Gerdes, 2011; Winters, Collett, & Myers, 2005). Practice guidelines suggest that ADHD assessment must include an accurate evaluation of both symptoms and related functional impairments (American Academy of Child and Adolescent Psychiatry, 2007; American Academy of Pediatrics, 2011; Canadian Attention Deficit Hyperactivity Disorder Resource Alliance [CADDRA], 2011).

The Weiss Functional Impairment Rating Scale (WFIRS; CADDRA, 2011) can be used as an appropriate measure in both clinical settings and treatment outcome trials. The WFIRS is a parent or self-report rating scale which assesses functional impairment specific to ADHD. By having multiple items in each domain, the WFIRS provides specific detail in each domain of impairment. The WFIRS is available in Polish, Swedish, Chinese, Danish, English, Spanish, Japanese, Norwegian, Thai, Urdu, German, French, Italian, and Turkish languages (CADDRA, 2011). Multiple studies across different countries have assessed the psychometric properties of the parent report version of the WFIRS (WFIRS-P; Dose, Hautmann, & Doepfner, 2016; Gajria et al., 2015; Qian, Du, Qu, & Wang, 2011; Tarakçıoğlu, Çakın Memik, Olgun, Aydemir, & Weiss, 2014; Weiss et al, 2007). The WFIRS-P has also shown sensitivity to treatment effects (e.g., Banaschewski et al., 2014; Hantson et al., 2012; Stein et al., 2015) with a significant correlation to ADHD symptom change (CADDRA, 2011).

There are two published studies (Canu, Hartung, Stevens, & Lefler, 2016; Takeda, Tsuji, Kanazawa, Sakai, & Weiss, 2017) validating the psychometric properties of the WFIRS self-report (WFIRS-S). In Canu et al. (2016), the validity and reliability of the WFIRS-S were assessed in a large sample of 18- to 25-years-old college students and the WFIRS-S demonstrated strong internal consistency, cross-informant reliability, and concurrent validity. A validation of the WFIRS-S in Japan also found the WFIRS-S had robust internal consistency, high test-retest reliability, and good convergent and discriminant validity in a sample of ADHD adults, control adults, and university students (Takeda et al., 2017).

To date, the psychometric properties of the WFIRS-S has never been tested either in an adolescent self-report sample or in a normative, non-ADHD sample. The aim of the current study is to assess the psychometric properties of a Persian translation of the WFIRS-S in a nonclinical school age sample of adolescents in Grades 7 to 12. Specifically, this study aims to assess the factor structure, internal consistency, test-retest reliability, interdomain correlations, and convergent validity of the WFIRS-S. Canu et al. noted (2016) that the WFIRS-S seemed to reliably assess functional impairment in a non-ADHD sample. We hypothesize that if the psychometric properties of the measure are maintained in this sample, which is distinct in the age of the informants, that they are a nonclinical sample, and in being from a distinct culture, this suggests that the domains and structure of functional impairment as measured by the WFIRS-S extends beyond any particular clinical, culture, or age group. These data could also then be used to develop more information about the epidemiology of functional success or impairment in the population at large, as well as develop appropriate cut-off scores for distinguishing clinical from nonclinical samples.

Method

Development Process of the Persian Form of the WFIRS-S

To assess the psychometric properties of the Persian version of the WFIRS-S, written permission from the developer of the scale was obtained. The translation of the scale to Persian was done by a PhD student in clinical psychology who had a good and sufficient understanding of the English language and research experience with ADHD. The measure was translated and back-translated by a clinical psychologist and researcher in ADHD who was fluent in both languages, with good fidelity as confirmed by the developer of the scale. The final Persian version was reviewed by several university students to assure face validity of the items.

Measures

WFIRS-S

The WFIRS-S developed by Margaret Weiss (CADDRA, 2011) is a self-report scale which is applicable for reporting the functional impairment associated with ADHD by adolescents and adults. It includes 69 items on a 4-point Likert scale: 0 (never or not at all), 1 (sometimes or somewhat), 2 (often or much), or 3 (very often or very much). In addition, items can be rated as “not applicable.” The items cover seven subdomains: Family (eight items, e.g., “Makes it hard for the family to have fun together”), Work (11 items, e.g., “Problems performing required duties”), School (10 items, e.g., “Problems completing assignments”), Life skills (12 items, e.g., “Excessive or inappropriate use of internet, video games, or TV”), Self-concept (five items, e.g., “Feeling frustrated with yourself”), Social activities (nine items, e.g., “Trouble getting along with people”), Risky activities (14 items, e.g., “Doing things that are illegal”). The scale can be scored as a whole and/or by domain using the mean of all items excluding those rated not applicable, ranging from 0 (never) to 3 (very much). This procedure allows for comparison between domains and a rating that is individualized to the functional impairment relevant to that individual. A simpler clinical procedure scores any domain as impaired if two items are rated as (2) much, or one item is rated as (3) very much.

Pediatric Quality of Life Inventory Version 4

0 Generic Core Scales (PedsQL 4.0). The PedsQL 4.0 (Varni, Seid, & Kurtin, 2001) was designed to assess the quality of life in children and adolescents aged 2 to 18 years old and includes generic core scales and disease-specific modules for different chronic conditions (e.g., Goldstein et al., 2008; Iannaccone et al., 2009; Varni, Limbers, Burwinkle, Bryant, & Wilson, 2008). The PedsQL 4.0 consists of 23 items on a 5-point response scale ranging from 0 (never a problem) to 4 (almost always a problem). The scores are reversed based on a 0 to 100 scale (0 = 100, 1 = 75, 2 = 50, 3 = 25, and 4 = 0) and higher scores show better quality of life. The PedsQL 4.0 includes four subdomains: Physical Functioning (eight items, e.g., “It is hard for me to walk more than one block”), Emotional Functioning (five items, e.g., “I feel afraid or scared”), Social Functioning (five items, e.g., “I have trouble getting along with other kids”), and School Functioning (five items, e.g., “It is hard to pay attention in class”). In this study, three scores were considered: the total score, the physical health total score, and the psychosocial health total score. The last score is obtained by summing up the scores of emotional, social, and school functioning subdomains. The PedsQL 4.0 has high internal consistency for the total score, Physical Health Score, and Psychosocial Health Summary Score (>0.80), and has also demonstrated validity (Varni et al., 2001). In an Iranian sample of adolescents, all subdomains of the PedsQL 4.0 self-report form had good internal consistency with Cronbach’s alpha ranging from .68 to .78 (Amiri et al., 2010). In the current study, reliability coefficients for the physical health scale, psychosocial health scale, and total scale were .77, .66, and .75, respectively.

Participants

The sample of the current study included 386 male and female adolescents (see Table 1) recruited from four public secondary schools (grades 7 to 12) in Shiraz, Iran. To be included in the study, participants had to be 12 to 18 years old and enrolled in one of the seven to 12 grades.

Table 1.

Participant Characteristics (n = 386).

Characteristic
Age (SD)	14.83 ± 1.76
Sex
Male	191 (49.5%)
Female	195 (50.5%)
Grade
Seventh	75 (19.4%)
Eighth	65 (16.8%)
Ninth	54 (14.0%)
Tenth	60 (15.5%)
Eleventh	77 (19.9%)
Twelfth	55 (14.2%)

Procedure

All participants provided informed consent. Participants were presented the necessary information about the aim of the study and instructions on how to complete the measure. Test-retest reliability was evaluated by having a subsample of 50 students complete the measure two weeks apart. To evaluate the convergent validity of the WFIRS-S, a different subsample of n = 100 participants completed the PedsQL 4.0 along with the WFIRS-S. The students filled out the questionnaires in a classroom setting which took approximately between 10 and 20 min. The data collection was anonymous and the scales were collected by independent psychology students.

Data Analysis

All analyses were conducted using IBM SPSS Statistics 22 and IBM SPSS Amos 22 programs. All statistical tests were run with a significance level of .05. Cronbach’s alpha coefficients were calculated to assess the internal consistency of the WFIRS-S for the total scale and each subdomain. Cronbach’s alpha coefficient greater than .9, .8, and .7, respectively, is considered excellent, good, and acceptable (George & Mallery, 2003). Pearson correlation coefficients were used to measure the relationships between subdomains with each other and with the summary scale of the WFIRS-S. Correlation coefficients below .29 is considered a small correlation, between .30 and .49 is moderate, and greater than .50 is a high correlation (Cohen, 1988). In addition, Pearson correlation coefficients were used to measure the test-retest reliability of the WFIRS-S. The minimal acceptable value for the test-retest reliability coefficient of a psychological test is usually considered .70 (Salkind, 2006). To evaluate the construct validity of the WFIRS-S, Confirmatory Factor Analysis (CFA) was done. First, the CFA was conducted for all 69 items of the WFIRS-S. Then, 12 items that were rated as “not applicable” by more than 50% of the sample were removed and the CFA was done for 57 items of the WFIRS-S. In CFA, to confirm the conceptual structure of the WFIRS-S, a seven-factor model based on the suggested structure for WFIRS-S (CADDRA, 2011) was examined. The comparative fit index (CFI) and the root mean square error of approximation (RMSEA) were considered to assess the goodness of fit of the CFA model. A value of CFI ≥ 0.90 (Hu & Bentler, 1999) and an RMSEA less than 0.10 (Brown & Cudeck, 1993) represent an acceptable model fit.

Results

WFIRS-S Descriptives

Mean scores and SD of each item and subdomain in the WFIRS-S are depicted in Table 2. The mean total score of the whole scale of the WFIRS-S was 0.31 (n = 386, SD = 0.29). Additionally, self-concept had the highest rated impairment (M = 0.45, SD = 0.68) and risky activities had the lowest (M = 0.17, SD = 0.30). The school, life skills, family, social activities, and work subdomains had the highest rated impairment to the lowest, respectively. Among the items, Item 8 from the family subdomain Item 10 from the school subdomain, and Item 1 from the risky activities subdomain had the highest rated impairments (M = 0.71-0.85) and Item 6 from the life skills subdomain and Items 11 and 12 from the risky activities subdomain had the lowest (M = 0.00).

Table 2.

WFIRS-S Item and Subdomain Mean Scores and SD.

	M	SD
Family	0.37	0.37
1. Having problems with family	0.46	0.72
2. Having problems with spouse/partner	0.19	0.75
3. Relying on others to do things for you	0.50	0.61
4. Causing fighting in the family	0.37	0.62
5. Makes it hard for the family to have fun together	0.17	0.51
6. Problems taking care of your family	0.25	0.59
7. Problems balancing your needs against those of your family	0.56	0.78
8. Problems losing control with family	0.85	0.90
Work	0.23	0.30
1. Problems performing required duties	0.49	0.64
2. Problems with getting your work done efficiently	0.45	0.69
3. Problems with your supervisor	0.40	0.79
4. Problems keeping a job	0.32	0.67
5. Getting fired from work	0.20	0.61
6. Problems working in a team	0.25	0.52
7. Problems with your attendance	0.25	0.63
8. Problems with being late	0.35	0.71
9. Problems taking on new tasks	0.40	0.61
10. Problems working to your potential	0.38	0.65
11. Poor performance evaluations	0.43	0.71
School	0.42	0.45
1. Problems taking notes	0.41	0.70
2. Problems completing assignments	0.46	0.70
3. Problems getting your work done efficiently	0.38	0.66
4. Problems with teachers	0.54	0.83
5. Problems with school administrators	0.42	0.83
6. Problems meeting minimum requirements to stay in school	0.26	0.83
7. Problems with attendance	0.27	0.60
8. Problems with being late	0.32	0.67
9. Problems with working to your potential	0.37	0.67
10. Problems with inconsistent grades	0.84	0.91
Life skills	0.41	0.40
1. Excessive or inappropriate use of internet, video games, or TV	0.56	0.89
2. Problems keeping an acceptable appearance	0.39	0.72
3. Problems getting ready to leave the house	0.37	0.76
4. Problems getting to bed	0.30	0.68
5. Problems with nutrition	0.45	0.78
6. Problems with sex	0.00	0.00
7. Problems with sleeping	0.40	0.73
8. Getting hurt or injured	0.41	0.67
9. Avoiding exercise	0.41	0.76
10. Problems keeping regular appointments with doctor/dentist	0.56	0.82
11. Problems keeping up with household chores	0.54	0.80
12. Problems managing money	0.62	0.94
Self-concept	0.45	0.68
1. Feeling bad about yourself	0.44	0.77
2. Feeling frustrated with yourself	0.50	0.83
3. Feeling discouraged	0.54	0.84
4. Not feeling happy with your life	0.52	0.88
5. Feeling incompetent	0.30	0.69
Social activities	0.32	0.40
1. Getting into arguments	0.57	0.76
2. Trouble cooperating	0.31	0.56
3. Trouble getting along with people	0.35	0.64
4. Problems having fun with other people	0.20	0.51
5. Problems participating in hobbies	0.18	0.49
6. Problems making friends	0.39	0.73
7. Problems keeping friends	0.27	0.59
8. Saying inappropriate things	0.38	0.71
9. Complaints from neighbors	0.27	0.67
Risk	0.17	0.30
1. Aggressive driving	0.71	0.97
2. Doing other things while driving	0.45	0.83
3. Road rage	0.37	0.80
4. Breaking or damaging things	0.26	0.64
5. Doing things that are illegal	0.31	0.69
6. Being involved with the police	0.14	0.48
7. Smoking cigarettes	0.06	0.35
8. Smoking marijuana	0.05	0.31
9. Drinking alcohol	0.14	0.51
10. Taking “street” drugs	0.04	0.32
11. Sex without protection (birth control, condom)	0.00	0.00
12. Sexually inappropriate behavior	0.00	0.00
13. Being physically aggressive	0.31	0.70
14. Being verbally aggressive	0.50	0.83

Note. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report.

Internal Consistency

Displayed in Table 3, the internal consistency of the WFIRS-S family and life skills subdomains were acceptable (α = .72 and .79, respectively), and were good for the work, school, social activities, and risky activities subdomains (αs = .80-.85). Additionally, excellent internal consistency was observed for the total scale (α = .94) and self-concept subdomain (α = .90).

Table 3.

Internal Consistency for WFIRS-S (n = 386).

WFIRS-S	Number of items	α
Family	8	.72
Work	11	.80
School	10	.82
Life skills	12	.79
Self-concept	5	.90
Social activities	9	.81
Risky activities	14	.85
Total	69	.94

Note. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report; α = Cronbach’s alpha coefficient.

WFIRS-S Subdomain and Total Score Correlations

Correlations between the WFIRS-S subdomains with each other were mostly statistically significant (p < .01) and ranged from small (r = .14-.28) to high (r = .54-.65) (see Table 4). The only exception was the correlation between work and life skills (r = .10) and also work and self-concept (r = .09). Robust and statistically significant correlations were found between the WFIRS-S total scale and each of the subdomains (r = .55-.80, p < .01).

Table 4.

Relationship Between WFIRS-S Subdomains With Each Other and With the Summary Scale (n = 386).

WFIRS-S	Family	Work	School	Life skills	Self-concept	Social activities	Risky activities	Total
Family	—
Work	.55**	—
School	.56**	.32**	—
Life skills	.46**	.10	.54**	—
Self-concept	.39**	.09	.42**	.56**	—
Social activities	.48**	.14**	.57**	.65**	.54**	—
Risky activities	.40**	.47**	.23**	.22**	.21**	.28**	—
Total	.80**	.70**	.70**	.63**	.55**	.66**	.67**	—

Note. Pearson’s correlation analysis. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report.

p < .01.

Test-Retest Reliability

Table 5 depicts the results of the test-retest subsample of students (n = 50). The test-retest coefficient reached the acceptable value for the risky activities subdomain (r = .70). The WFIRS-S total score, school, self-concept, and social activities subdomains exceeded the acceptable value (r = .72-.87). For the family, work, and life skills subdomains, the correlation coefficients were less than the standard magnitude (r = .59-.66).

Table 5.

Results of Test–Retest Reliability (n = 50).

WFIRS-S	Test		Retest		r
WFIRS-S	M	SD	M	SD	r
Family	0.28	0.27	0.16	0.23	.63**
Work	0.13	0.29	0.10	0.16	.59**
School	0.33	0.43	0.28	0.39	.72**
Life skills	0.35	0.36	0.31	0.42	.66**
Self-concept	0.22	0.49	0.25	0.60	.75**
Social activities	0.27	0.42	0.22	0.45	.87**
Risky activities	0.16	0.32	0.18	0.38	.70**
Total	0.25	0.29	0.21	0.28	.80**

Note. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report; r = Pearson’s correlation coefficient.

p < .01.

Convergent Validity

The correlations of the WFIRS-S subdomains and summary scale with the PedsQL subdomains and total score are reported in Table 6. All the correlations between the WFIRS-S subdomains and the PedsQL physical health subdomain were low to moderate and statistically significant (r = −.29 to −.46, p < .01) with the exception of risky activities. High and significant correlations were found for the WFIRS-S subdomains and the PedsQL psychosocial score (r = −.62 to −.74, p < .01), and moderate and statistically significant correlations for work and risky activities (r_s = −.41 and −.42, respectively, p < .01). The WFIRS-S summary scale indicated moderate and significant correlation with the PedsQL physical health subdomain (r = −.45, p < .01) and high and significant correlation with the PedsQL psychosocial health summary scale and total scale (r = −.81 and −.79, respectively, p < .01).

Table 6.

Correlations Between WFIRS-S and PedsQL (n = 100).

WFIRS-S	PedsQL		Total
	Physical health	Psychosocial health	Total
	r	r	r
Family	−.46**	−.62**	−.64**
Work	−.29**	−.41**	−.42**
School	−.36**	−.71**	−.69**
Life skills	−.46**	−.74**	−.74**
Self-concept	−.38**	−.68**	−.66**
Social activities	−.35**	−.73**	−.69**
Risky activities	−.08	−.42**	−.36**
Total	−.45**	−.81**	−.79**

Note. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report; PedsQL = Pediatric Quality of Life Inventory; r = Pearson’s correlation coefficient.

p < .01. *p < .05.

CFA

The results of the CFA for all 69 items of the WFIRS-S indicated that the CFI was 0.60 and another index of model fit, RMSEA, was 0.08 and within the range of acceptable model fit (<0.10). Additionally, the findings of the CFA for 57 items of the WFIRS-S demonstrated that the CFI was 0.70 and RMSEA was 0.07.

Discussion

This study assessed the reliability and validity of the Persian version of the WFIRS-S in a sample of Iranian adolescents aged 12 to 18 years. This is the first research in Iran adapting a Persian scale for assessing functional impairment in adolescents. Internal consistency of the subdomains was acceptable (0.72-0.90) and internal consistency for the total scale of the WFIRS-S was excellent (0.94). Generally, the findings of internal consistency in this study are consistent with the results of the previous studies on the WFIRS-S (CADDRA, 2011; Canu et al., 2016; Takeda et al., 2017).

Test-retest reliability coefficients were between .70 and .87 for the total scale, risky activities, school, self-concept, and social activities subdomains and between .59 and .66 for the family, work, and life skills subdomains. These results are consistent with the findings of Takeda et al. (2017), and the results for the life skills and self-concept subdomains close to identical. This suggests not only that the measure itself has test-retest reliability but also that patients from widely diverse cultural backgrounds show a similar level of consistency in reporting on their functional impairment over time.

The domains of the WFIRS-S showed a small to moderate correlation with each other, but the correlation between individual domains and the scale as a whole was moderate to large (.55 to .80). Among the subdomains, the self-concept had the lowest correlation with the total scale. This suggests that while functional impairment can be variable across domains, the impairment in any given domain tends to be consistent with functional impairment overall.

This is the first published report of interdomain correlations on the WFIRS-S. However, we can compare our results with two previous studies (Tarakçıoğlu et al., 2014; Weiss et al., 2007) on the parent report form of the WFIRS (WFIRS-P). In Weiss et al.’s (2007) study, the correlations between the WFIRS-P subdomains and the total scale ranged from .52 to .82 and in Tarakçıoğlu et al.’s (2014) study, were between .64 and .85. Also, like the results of the current study, in these studies (i.e., Tarakçıoğlu et al., 2014; Weiss et al., 2007), the self-concept subdomain had the lowest correlation with the total scale of the WFIRS-P. Self-concept as the cognitive component of self-evaluation (Marsh & Craven, 2006) can be defined as how a person thinks and feels about him/herself (Glenn & Cunningham, 2001) and is correlated with quality of life (Dolgun, Savaşer, & Yazgan, 2013). The five self-concept items of the WFIRS-S need a person’s subjective evaluation (e.g., “Feeling bad about yourself”) and are related to quality of life; however, the other subdomains of the WFIRS-S include items that need a person’s objective evaluation (e.g., “Problems completing assignments”) and are related to functional impairment. This would suggest that how patients with ADHD feel about themselves is not as tightly correlated as the level of functioning they obtain in different areas.

To assess the convergent validity of the WFIRS-S, the correlations of the WFIRS-S subdomains and total scale with the self-report form of the PedsQL were studied. Generally, the correlation between functional impairment and physical health was low to moderate where the correlation to psychosocial health was moderate to high. It makes inherent sense that functional impairment impacts psychosocial wellbeing more than physical health, a finding that is consistent with Tarakçıoğlu et al.’s (2014) study on the WFIRS-P. The strength of the correlation between functional impairment as measured by the WFIRS and psychosocial health may reflect both the similarity in content of the actual items, as well as there being a greater overlap between functioning and psychosocial wellbeing than between functioning and physical health. Our findings demonstrate that just as functional impairment and quality of life have been shown to be overlapping but distinct concepts in children and adults with ADHD, the same holds true for a nonclinically identified group of adolescents.

The construct validity of the WFIRS-S was assessed through a CFA. The results of CFA for all items of the WFIRS-S showed a satisfactory seven-factor model by the RMSEA criterion. Rigdon (1996) believes that use of CFI index is more problematic for goodness of fit in confirmatory contexts than RMSEA because of CFI baseline model. Additionally, the model was improved by removing 12 items that were rated as “not applicable” by more than half of the students and both fit indices (CFI and RMSEA). Some items of the WFIRS-S may not be applicable to adolescents in Iran, so it is expected that they are rated as “not applicable.” These items concerned having a spouse/partner, work, experiencing sex, and driving may all be not applicable for age appropriate reasons. Therefore, removing these items led to an improved model fit and should be taken into consideration when using the WFIRS-S with an adolescent sample.

In this study, many participants had scored 0 (never or not at all) across all items so the mean total score of the whole scale of the WFIRS-S was 0.31. Each item had a high proportion of respondents scoring zero. However, it makes sense for a floor effect to be observed in a nonclinical sample when administering a scale used to measure impairment or abnormal symptoms. It did not appear that a floor effect impacted the effectiveness of the WFIRS-S. It is notable that a total scale mean score of 0.31 is more than a full standard deviation below the mean score of 0.88 found in a U.S. adult group with ADHD assessed by the WFIRS-S (Canu et al., 2016) and the mean score of about 1.0 found in multiple child samples with ADHD assessed by the WFIRS-P (Dose et al., 2016; Gajria et al., 2015). Among the WFIRS-S subdomains, the risky activities subdomain had the lowest mean score that this is consistent with Takeda et al.’s (2017) study on the WFIRS-S. In Takeda et al.’s (2017) study, all groups including ADHD group, non-ADHD student group, and the non-ADHD adult group showed the lowest mean score in the risky activities subdomain. Additionally, the self-concept subdomain had the highest mean score. This finding is consistent with the previous studies (Canu et al., 2016; Takeda et al., 2017) on the WFIRS-S in adults with and without ADHD.

The limitation of this investigation, as well as its strength, is that the WFIRS-S is asking about how emotional difficulties impact perceived capacity to function. This means that even in a nonclinical sample, adolescents still perceive themselves as both having emotional challenges that impact their functioning, even if these emotional difficulties are not necessarily within above a clinical threshold. This is a question that is clinically important, that has not previously been investigated. The fact that the WFIRS-S has psychometric validity in a normal sample means that the norms obtained can be used as a comparison for a range of clinical groups, and that the items are not necessarily unique or specific to ADHD. While previous studies, for example of the SNAP-IV rating scale (Bussing et al., 2008), have obtained normative values to assist in defining what should be considered symptomatic, this has not previously been done for functional impairment.

Future studies should assess the psychometric properties of the Persian version of the WFIRS-S in an ADHD or other clinical sample of Iranian adolescents to learn more about the ROC characteristics that distinguish different populations on this measure.

Conclusion

This is the first validation of the use of the WFIRS-S in a public school sample of adolescents. Additionally, this is the first report of the Persian version of the WFIRS-S. The WFIRS-S was found to have the same robust psychometric properties when used in adolescents as adults, and in a non-ADHD population as it did in an ADHD population. This suggests that the measure can be used across cultures, age groups, and disorders. Future research should explore whether the WFIRS-P can also be used in non-ADHD populations, and how parent and adolescent self-report of functioning compare.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Author Biographies

Habib Hadianfard, PhD, is a professor of clinical psychology at Shiraz University. His primary research interest is ADHD. In recent decades, he has been struggling to make the ADHD assessment tools and treatment Compatible with Persian culture and language.

Behnaz Kiani, MA, is a doctoral student in clinical psychology at Shiraz University. Her research interests include assessment and treatment of ADHD. She is also interested by the effects of mindfulness meditation training on ADHD symptoms and associated impairments in children and adolescents.

Margaret D. Weiss, MD, PhD, Dr. Weiss is currently the Director of Child and Adolescent Psychiatry at University of Arkansas Medical Sciences. Dr. Weiss has extensive clinical experience in all aspects of child psychiatry, including inpatient, general outpatient and consultation/liaison. She received her MD and Fellowship in Psychiatry from McGill University and a PhD in the History of Science from Harvard University. She has published over 100 peer-reviewed articles, and authored the book ADHD in Adulthood: A Guide to Current Theory, Diagnosis, and Treatment. She is known as a world expert in ADHD, melatonin and sleep, developer of the Weiss Functional Impairment Rating Scale, and the CADDRA guidelines for ADHD.

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Psychometric Properties of the Persian Version of the Weiss Functional Impairment Rating Scale–Self-Report Form in Iranian Adolescents

Abstract

Keywords

Introduction

Method

Development Process of the Persian Form of the WFIRS-S

Measures

WFIRS-S

Pediatric Quality of Life Inventory Version 4

Participants

Procedure

Data Analysis

Results

WFIRS-S Descriptives

Internal Consistency

WFIRS-S Subdomain and Total Score Correlations

Test-Retest Reliability

Convergent Validity

CFA

Discussion

Conclusion

Footnotes

Declaration of Conflicting Interests

Funding

Author Biographies

References