Validation of the French Version of the Weiss Functional Impairment Rating Scale–Self-Report in a Large Cohort of Adult Patients With ADHD

Abstract

Objective: To analyze the psychometric properties of the French version of the Weiss Functional Impairment Rating Scale–Self Report (WFIRS-S) in a large clinical sample of adults with ADHD. Method: Patients (N = 363) were diagnosed with ADHD according to the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) criteria. Psychometric properties of the French version of the WFIRS-S were tested including construct validity with a confirmatory factor analysis, internal structural validity with Cronbach’s alpha coefficient, external validity by correlations with the Beck Depression Inventory–II (BDI-II), and the EuroQol five-dimension (EQ-5D) questionnaire. Results: The confirmatory factor analysis found the following: root mean square error of approximation (RMSEA) = 0.061, 90% confidence interval (CI) = [0.058, 0.063]; comparative fit index (CFI) = 0.67. Cronbach’s alpha coefficient was .91. Correlations with EQ-5D descriptive index, visual analogue scale (VAS) scores, and BDI-II scores were –0.48, –0.55, and 0.53, respectively. Conclusion: The French version of the WFIRS-S is a psychometrically acceptable self-reported questionnaire for the multi-domain evaluation of functional impairments in adults with ADHD, for research and clinical purposes.

Keywords

ADHD functional impairment Weiss Functional Impairment Rating Scale–Self-Report form psychometric properties

Introduction

ADHD is one of the most prevalent psychiatric disorders that starts in childhood and often persists into adulthood. Its estimated prevalence ranges from 3% to 5% in adults (Caci, Morin, & Tran, 2014; Fayyad et al., 2007; Hudziak, Althoff, Derks, Faraone, & Boomsma, 2005; Kessler et al., 2006). Inattention, hyperactivity, and impulsivity are the core symptoms (American Psychiatric Association [APA], 2000). However, besides having a symptomatic description of ADHD, it seemed necessary to adopt a more holistic approach to the disorder to better capture patients’ everyday life functioning as an indicator of their well-being and perceived health, thereby predicting future function and need for treatment (Able, Johnston, Adler, & Swindle, 2007; Asherson, 2005). Appropriate therapeutic interventions may thus be designed, in particular, by identifying the goals of treatment and measuring its usefulness according to various aspects of ADHD-related functioning (Brod, Perwien, Adler, Spencer, & Johnstone, 2005; Weiss & Murray, 2003).

While the core symptoms have been related to large and variable functional impairment (Kessler et al., 2006; Stern, Pollak, Bonne, Malik, & Maeir, 2017) in ADHD, they cannot alone explain all the functional impairment observed (Able et al., 2007). Psychiatric comorbidities such as depressive disorder and traumatic stress disorder (Jensen, Martin, & Cantwell, 1997; Matthies, Sadohara-Bannwarth, Lehnhart, Schulte-Maeter, & Philipsen, 2016), concomitant sleep disorders such as sleep apnea syndrome (Bioulac, Micoulaud-Franchi, & Philip, 2015), and affective traits such as affective lability (He, Antshel, Biederman, & Faraone, 2015; Weibel et al., 2017) are also associated with an impairment in functioning in ADHD. Thus, ADHD symptoms and actual functional impairment overlap but are distinct concepts. It is important to measure both as some patients exhibit a high level of core symptoms but are not functionally impaired, or vice-versa. Moreover, practice guidelines recommend that ADHD assessment should include an accurate evaluation of both symptoms and related functional impairments (American Academy of Child and Adolescent Psychiatry, 2007; Asherson, 2005; Canadian ADHD Resource Alliance [CADDRA], 2011; Nutt et al., 2007).

The Weiss Functional Impairment Rating Scale (WFIRS-S) is a self-report scale designed to assess ADHD-related functional impairments in various relevant subdomains for adolescents and adults (CADDRA, 2011; Canu, Hartung, Stevens, & Lefler, 2016; Weiss, 2000), which are likely to represent the target for treatment. Therefore, the use of the scale before and after treatment can allow the clinician to determine not only whether the ADHD has improved but also whether the patient’s functional difficulties have also been alleviated (Canu et al., 2016). The WFIRS-S is a multilingual tool for the worldwide assessment of functional impairment in ADHD and has already been translated into 18 languages. The original version was published by CADDRA in both French and English (www.caddra.ca). Translating questionnaires may be dependent on cultural background so before using any translated questionnaire, a transcultural validation must be performed according to specific rules and methods (Brislin, 1970). Despite French being the sixth most widely spoken language in the world with 220 million speakers (Organisation International de la francophonie, 2009), the French version of the WFIRS-S has not previously been validated.

A recent psychometric study of the English WFIRS-S demonstrated good psychometric properties, with a good internal consistency for each domain and for the overall scale and a good external validity with other measures of functioning (Canu et al., 2016). Robust psychometric properties were also confirmed in the Japanese (Takeda, Tsuji, Kanazawa, Sakai, & Weiss, 2016) and Persian (Hadianfard, Kiani, & Weiss, 2017) versions. Limitations of these studies include that they were conducted with student samples from 12- to 25-year-old (Canu et al., 2016; Hadianfard et al., 2017), with a majority of subjects included being not affected with ADHD. Only the Japanese study included a small sample of adults with a clear diagnosis of ADHD (N = 46). As the WFIRS-S has been designed to support the clinical evaluation of functioning in adults diagnosed with ADHD, the psychometric properties of this scale should also be assessed in large clinical samples of adults with an established diagnosis of ADHD, in all age groups. This study will report the validation of a French version of the WFIRS-S, so as to facilitate further clinical evaluation and research on functional impairment in specific domains in a large clinical sample of native French-speaking patients with ADHD diagnosed according to a structured face-to-face standardized interview.

Method and Materials

Participants

From November 2011 to December 2017, 363 patients (188 males, median age 33 years, range 18-71) diagnosed with ADHD according to Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; APA, 2013) criteria were recruited at the adult ADHD outpatient clinic of the department of neurology in Montpellier, France. All patients were psychostimulant-naive at the time of the study.

All patients underwent a structured interview on ADHD (Diagnostic Interview for Adult ADHD, second edition [DIVA-2], available on http://www.divacenter.eu/DIVA.aspx) with experienced clinicians (R.L., M.G.) to assess the presence of 18 symptoms and the related impairment in childhood (primary school, age 6-12 years, mostly based on informant and school reports) and currently. The DIVA-2 is a reliable tool for assessing and diagnosing ADHD with an excellent concurrent validity (Kooij et al., 2008; Ramos-Quiroga et al., 2016). For this study, the DIVA-2 was slightly modified to fulfill the recent DSM-5 criteria for adult ADHD. Based on the DSM-5 criteria, three ADHD clinical presentations were defined at the time of the interview: (a) predominantly inattentive (ADHD-PI), in the presence of at least five inattention symptoms and fewer than five hyperactive–impulsive symptoms; (b) predominantly hyperactive–impulsive (ADHD-HI), requiring at least five hyperactivity–impulsivity symptoms and fewer than five inattention symptoms; and (c) combined (ADHD-C), when at least five inattention and five hyperactive–impulsive symptoms were reported. The clinical evaluation also assessed the diagnosis of lifetime and actual depressive episodes, and lifetime history of substance use disorder, according to the DSM-5 criteria.

All patients completed a battery of self-report questionnaires. The Conners’ Adult ADHD Rating Scale–Self-Report: Short Version (CAARS-S:S) assessed the severity of ADHD symptoms. The CAARS-S:S includes 26 items rated from 0 (not at all, never) to 3 (very much, very frequently) (Conners, Erhardt, Epstein et al., 1999). Five indexes can be computed (inattention/memory problems, hyperactivity/restlessness, impulsivity/emotional lability, problems with self-concept, and an overall ADHD index). The raw indexes were transformed into t scores based on age and sex norms. The Wender Utah Rating Scale (WURS-25; Caci, Bouchez, & Bayle, 2010; Ward, Wender, & Reimherr, 1993) is a self-rating scale that retrospectively assesses ADHD-relevant childhood behaviors and symptoms. All 25 items are rated from 0 (not at all or very slightly) to 4 (very much), and a total score can be computed ranging from 0 to 100. The 21-item Beck Depression Inventory–II (BDI-II) measures the severity of self-reported depressive symptoms (Beck, Ward, Mendelson, Mock, & Erbaugh, 1961). Each symptom is rated on a 4-point scale ranging from 0 to 3, and total scores can range from 0 to 63.

A subgroup of 97 patients also completed the EuroQol five-dimension (EQ-5D) questionnaire. This simple instrument provides a generic measure of health outcomes for a wide range of health conditions (Herdman et al., 2011). It consists of two sections, the EQ-5D descriptive system and the visual analogue scale (VAS). The descriptive section assesses five dimensions of health-related quality of life (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), each described by three response levels (no, some, or extreme problems). An index score can be calculated from individual descriptive responses. The EQ-5D VAS scores are anchored on 100 = best imaginable health and 0 = worst imaginable.

The participants provided informed consent. The study was conducted in accordance with the Declaration of Helsinki and French Good Clinical Practices.

French Version of WFIRS-S

Translation of WFIRS-S

The WFIRS-S has been available for use in the public domain to encourage clinicians to assess functional impairment as part of the diagnostic work up and to look at functional improvement and remission with treatment. It can be copied without permission, but the instrument must remain as published without modification to protect its integrity (CADDRA, 2011). To assess the psychometric properties of the French version, we used the version freely available on http://www.caddra.ca/cms4/pdfs/fr_caddraGuidelines2011WFIRS_S.pdf.

The French (Quebec) version of the WFIRS-S was developed using a forward–backward translation procedure. We ensured the clarity and cultural acceptability of this French version of the WFIRS-S in French (France) ADHD by administering it to 10 patients. This pretest did not show any difficulties in understanding the items of the French version so no adaptations were required.

The French version of the WFIRS-S includes 69 items on a 4-point Likert-type 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, for example, “Having problems with family”), work (11 items, for example, “Problems with getting your work done efficiently”), school (10 items, for example, “Problems meeting minimum requirements to stay in school”), life skills (12 items, for example, “Problems keeping up with household chores”), self-concept (five items, for example, “Feeling incompetent”), social activities (nine items, for example, “Problems participating in hobbies”), and risky activities (14 items, for example, “Breaking or damaging things”).

Scoring

The same method of scoring was used as in the original paper validating the WFIRS-S (Canu et al., 2016). The mean of the item responses was calculated for each of the seven domains: “family,” “work,” “school,” “life skills,” “self-concept,” “social activities,” and “risky activities.” Items with a “not applicable” response were removed for the computation of the mean scores to prevent distortions from “not applicable” responses. For clinical purposes with the original version of the WFIRS-S, when defining impairment for DSM-5, clinicians can consider that any domain with a mean score >1.5 is impaired (CADDRA, 2011).

Statistical Analyses and Hypotheses

Descriptive statistics of the obtained data included frequencies and percentages of categorical variables together with means and standard deviations of continuous variables. For the validation process, we analyzed the psychometric properties of the French version including construct validity, internal structural validity, and external validity. Significance level was set at p = .05. Analyses were performed using SPSS software (Version 18 for Mac, PASW Statistics) and Stata software (Version 14 for Mac, StataCorp).

Construct validity

A confirmatory factor analysis (CFA) was performed using the LISREL model to analyze the construct validity and to test the three-factor structure of the original scale. To use the questionnaires of all participants, even those with “not applicable” responses (considered in the model as “missing value”), the maximum likelihood for missing values method was used (Truxillo, 2005). This procedure generates estimates using maximum likelihood for missing values, sometimes called full information maximum likelihood (FIML). The following indicators were required to be considered acceptable (Botha, Shapiro, & Steiger, 1988): a root mean square error of approximation (RMSEA) less than 0.08 and a comparative fit index (CFI) greater than 0.9. A subsequent sensitivity analysis was performed using listwise deletion (complete case method). Correlations between each subdomain of the WFIRS-S and the total scores were investigated by computing Spearman’s coefficients.

Internal structural validity

Item internal consistency (IIC) was assessed by correlating each item with its related factor; correlations of at least .4 are recommended for supporting IIC (Carey & Seibert, 1993). Item discriminant validity (IDV) was assessed by determining whether items correlated better with the factor they were hypothesized to represent compared with the other factor (Campbell & Fiske, 1959). IIC are correlations between items and the factor that they are hypothesized to represent, and IDV are correlations between items and the other dimensions that they are not hypothesized to represent. Therefore, the IIC and IDV ranges should not overlap to be considered as satisfactory. For each dimension, internal consistency reliability was assessed by Cronbach’s alpha coefficient and was recalculated after items were removed. To confirm consistency, a coefficient of at least 0.7 was expected (Cronbach & Meehl, 1955). It is recommended that deletion of any of the items should not increase Cronbach’s alpha coefficient. Floor and ceiling effects were reported to assess the distribution of the responses. The rate of floor and ceiling effects was calculated as the proportion of individuals who obtained the lowest (“never or not at all”) and the highest (“very often or very much”) scores for any of the items.

External validity

To explore the concurrent external validity, the relation between WFIRS-S score and EQ-5D scores (EQ-5D index and VAS score) was investigated by computing Spearman’s coefficients. To explore the divergent external validity, the relation between each WFIRS subdomains scores and age, CAARS-S:S subscores, and BDI-II was investigated by computing Spearman’s coefficients. Coefficients below .3 corresponded to small correlations; coefficients from .3 to .5 and those above .5 corresponded to moderate and high correlations, respectively. Gender-related differences in WFIRS-S scores were investigated by the Mann–Whitney test.

Results

Sample Characteristics

Demographic data and clinical characteristics at the time of the evaluation are presented in Table 1. There were 115 students (31.7%), 86 (23.7%) patients were unemployed, and five patients (1.4%) were retired. In all, 221 (60.8%) patients had achieved a university grade. ADHD-PI presentation was currently diagnosed in 159 patients (43.8%), ADHD-C in 188 patients (51.8%), and ADHD-HI in 15 patients (4.1%). CAARS-S:S scores revealed severe (>1 SD) inattention/memory problems, hyperactivity/restlessness, and emotional lability/impulsivity symptoms in 316 (87.1%), 216 (59.5%), and 234 (64.4%) patients, respectively. The median CAARS-S:S ADHD index score was 74 (range 48-90). The median WURS score was 56 (range 12-94), with 88.2% of patients having a score above 36. A familial history of ADHD diagnosis was found in 133 patients (36.6%). A lifetime history of depression was found in 217 (59.7%) patients, and 72 (19.8%) met the criteria for major depressive episode. The median BDI score was 20 (range 0-55), and 93 (25.6%) patients had a BDI score above 29. A lifetime history of substance use disorder was found in 140 patients (38.6%). Eighty-two patients (22.6%) were taking at least one psychotropic or sedative drug including the following: antidepressants (n = 51; 14.0%), anxiolytics (n = 28; 7.7%), mood stabilizers (n = 16; 4.4%), antipsychotics (n = 15; 4.1%), hypnotics (n = 14; 3.8%), and opioids (n = 6; 1.7%).

Table 1.

Demographic and Clinical Characteristics of the Participants.

	n (% of missing values)	M (SD)	Median (minimum-maximum)
Demographic characteristics
Age, in years	363 (0.0%)	33.72 (10.65)	33.0 (18-71)
Sex	363 (0.0%)
Male		188 (51.8%)^a
Female		175 (48.2%)^a
BMI, in kg/m²	337 (7.1%)	23.17 (3.8)	22.6 (16-39)
Clinical characteristics
CAARS-S:S
CAARS-S:S IMP	361 (0.05%)	72.02 (9.60)	73.0 (42-90)
CAARS-S:S HR	361 (0.05%)	62.53 (10.23)	63 (32-83)
CAARS-S:S IE	361 (0.05%)	64.87 (11.61)	65 (40-90)
CAARS-S:S SC	361 (0.05%)	65.83 (9.32)	68 (36-85)
CAARS-S:S index	361 (0.05%)	73.44 (9.31)	74 (14-90)
WURS-25	363 (0.0%)	56.40 (16.41)	56 (12-94)
BDI-II	360 (0.08%)	21.44 (11.66)	20 (0-55)
Quality of life
EQ-5D descriptive index	97 (73.3%)	0.66 (0.21)	0.69 (0.15-1)
VAS EQ-5D	97 (73.3%)	65.82 (16.89)	70 (10-95)

Note. BMI = body mass index; CAARS-S:S = Conners’ Adult ADHD Rating Scales–Self-Report: Short Version; CAARS-S:S IMP = CAARS-S:S impulsivity/emotional lability factor; CAARS-S:S HR = CAARS-S:S hyperactivity/restlessness factor; CAARS-S:S IEL = CAARS-S:S inattention/memory problem factor; CAARS-S:S SC: CAARS-S:S problems with self-concept factor, WURS-25 = Wender Utah Rating Scale, BDI = Beck Depression Index; EQ-5D = EuroQol five-dimension questionnaire; VAS = visual analogue scale.

Dichotomous variables are expressed as number and percentages.

Validity

Construct validity

As the items of the “school” subdomain of the WFIRS-S exhibited a high rate of “not applicable” responses (>20%), a CFA was performed only for the remaining items (i.e., 59 items). The CFA revealed that the indicators were satisfactory: RMSEA = 0.061, 90% confidence interval (CI) = [0.058, 0.063]; CFI = 0.67. The sensitivity analysis was conducted with 146 complete observations and found the following fit indexes: RMSEA = 0.074, 90% CI = [0.069, 0.078]; CFI = 0.572. Correlations between each subdomain of the WFIRS-S and the total scores are shown in Table 2. We found significant correlations between each subdomain of the WFIRS-S (from ρ = .14 to ρ = .51). Correlations between WFIRS-S subdomains and the total mean score were high (from ρ = .56 to ρ = .78).

Table 2.

Relationship Between WFIRS-S Subdomains and With Overall Score (N = 363).

WFIRS-S subdomains	Family	Work	School	Life skills	Self-concept	Social activities	Risky activities	Total
Family	—
Work	.34**	—
School	.31**	.46**	—
Life skills	.46**	.51**	.43**	—
Self-concept	.33**	.36**	.32**	.42**	—
Social activities	.46**	.41**	.33**	.51**	.38**	—
Risky activities	.36**	.28**	.35**	.34**	.14**	.35**	—
Total	.67**	.71**	.68**	.78**	.56**	.71**	.63**	—

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

p < .01.

Internal structural validity

IIC was satisfactory for the seven factors, each item achieving the 0.40 standard threshold value except Items 1 and 9 from the “social activity” factor: “Getting into arguments” (ρ = .20) and “Complaints from neighbors” (ρ = .27). IDV was satisfactory as the correlation between items with their contributive factor was higher than for items with the other factor except for Item 9 from the “social activity” factor: “Complaints from neighbors,” which correlated more strongly with the “risky activities” factor than with its original factor “social activity.” Note that Item 3 from the “life skills” factor—“Problems getting ready to leave the house”—also achieved the 0.40 standard threshold for the “work” factor (see Table 3).

Table 3.

French WFIRS-S Factor Characteristics (N = 363).

WFIRS-S subdomains	Number of items	M (SD)	Cronbach’s α	IIC (minimum-maximum)	IDV (minimum-maximum)
Family	8	1.66 (0.72)	.83	(0.49-0.74)	(0.11-0.37)
Work	11	1.52 (0.67)	.82	(0.49-0.69)	(0.01-0.49)
School	10	1.74 (0.60)	.81	(0.48-0.66)	(0.07-0.38)
Life skills	12	1.49 (0.57)	.73	(0.39-0.61)	(0.11-0.35)
Self-concept	5	2.21 (0.73)	.84	(0.73-0.80)	(0.06-0.38)
Social activities	9	1.35 (0.59)	.75	(0.20-0.74)	(0.01-0.36)
Risky activities	14	0.82 (0.53)	.78	(0.35-0.62)	(0.01-0.32)
Total	69	1.43 (0.42)	.91	—	—

Note. WFIRS-S: Weiss Functional Impairment Rating Scale–Self-Report; IIC = item internal consistency (item-to-own dimension correlations); IDV = item discriminant validity (item-to-other dimensions correlations).

Cronbach’s alpha coefficient was .91 for the overall scale and was not higher after items were removed. However, for “family” (α = .83) the deletion of Item 4 gave a Cronbach’s alpha coefficient of .84, while for “social activities” (α = .75) the deletion of Items 1 and 9 gave a Cronbach’s alpha coefficient at .78 and .76, respectively. For “work,” “school,” “life skills,” “self-concept,” and “risky activities,” Cronbach’s alpha coefficients were not higher after items were removed. The overall internal consistency was thus satisfactory (see Table 3).

Floor and ceiling effects ranged from 3.6% to 80.7%, and from 2.5% to 67.8%, respectively. The rate of “not applicable” responses was higher for the items of “school,” “work,” for some items of the “family” subdomain related to spouse/partner and parenting, and “risky activities” items related to driving (see Table 4).

Table 4.

French WFIRS-S items and characteristics (N = 363).

Items	M	SD	Not applicable response (%)	Floor (%)	Ceiling (%)
Family	1.66	0.72
1. Having problems with family	2.03	0.96	5.5	7.9	39.7
2. Having problems with spouse/partner	1.96	1.04	15.4	12.1	40.4
3. Relying on others to do things for you	1.50	1.07	4.1	24.7	20.7
4. Causing fighting in the family	1.52	1.11	5.8	25.1	24.9
5. Makes it hard for the family to have fun together	1.14	1.07	8.8	37.2	13.9
6. Problems taking care of the family	1.62	1.07	16.3	20.4	25.7
7. Problems balancing your needs against those of your family	1.69	1.08	16	18.7	29.2
8. Problems losing control with family	1.99	1.04	6.9	12.4	41.1
Work	1.53	0.67
1. Problems performing required duties	1.84	1.02	7.4	12.2	33
2. Problems with getting your work done efficiently	1.94	1.04	10.5	12.9	39.1
3. Problems with your supervisor	1.44	1.11	13.8	26.5	23.3
4. Problems keeping a job	1.34	1.22	16.3	37.8	25.7
5. Getting fired from work	0.84	1.11	17.6	56.9	14.7
6. Problems working in a team	1.45	1.12	9.6	26.8	24.1
7. Problems with your attendance	0.88	1.11	8.8	52.3	15.7
8. Problems with being late	1.35	1.22	8.3	35.7	27
9. Problems taking on new tasks	1.48	1.07	7.2	22.6	22.8
10. Problems working to your potential	2.41	0.89	7.4	5.7	63.1
11. Poor performance evaluations	1.63	1.10	17.6	21.1	27.8
School	1.74	0.60
1. Problems taking notes	2.15	0.91	23.4	5.4	45
2. Problems completing assignments	2.28	0.84	22.9	4.6	48.6
3. Problems getting your work done efficiently	2.06	0.87	22.9	5	36.4
4. Problems with teachers	1.19	1.05	24.2	31.3	16
5. Problems with school administrators	0.96	1.03	25.1	44.5	11.4
6. Problems meeting minimum requirements to stay in school	1.31	1.11	25.3	32.1	19.2
7. Problems with attendance	1.21	1.16	23.7	38.6	20.6
8. Problems with being late	1.48	1.19	23.1	29.4	29
9. Problems with working to your potential	2.52	0.82	24	5.4	67.8
10. Problems with inconsistent grades	2.25	0.96	24.8	7	54.6
Life skills	1.49	0.57
1. Excessive or inappropriate use of Internet, video games, or TV	1.85	1.14	0.8	18.9	39.7
2. Problems keeping an acceptable appearance	0.47	0.78	1.4	68.2	3.1
3. Problems getting ready to leave the house	1.72	1.20	0.6	23.8	38
4. Problems getting to bed	1.92	1.17	1.7	19.6	45.1
5. Problems with nutrition	1.43	1.14	1.9	29.5	23.9
6. Problems with sex	1.14	1.18	6.6	43.1	20.4
7. Problems with sleeping	2.06	1.00	1.7	9.2	44.3
8. Getting hurt or injured	0.95	1.02	1.1	43.7	11.4
9. Avoiding exercise	1.28	1.15	2.2	34.6	21.7
10. Problems keeping regular appointments with doctor/dentist	1.42	1.12	2.8	27.8	23.2
11. Problems keeping up with household chores	1.79	1.12	1.4	18.2	36.3
12. Problems managing money	1.80	1.16	1.4	19.3	39.7
Self-concept	2.21	0.73
1. Feeling bad about yourself	2.26	0.94	1.9	5.9	55.1
2. Feeling frustrated with yourself	2.32	0.89	2.5	5.9	55.1
3. Feeling discouraged	2.34	0.84	1.4	3.6	54.5
4. Not feeling happy with your life	2.13	0.97	1.7	7.3	47.3
5. Feeling incompetent	2.01	1.04	1.4	11.5	43
Social activities	1.35	0.59
1. Getting into arguments	2.01	0.96	2.2	6.5	40
2. Trouble cooperating	1.33	0.91	2.5	18.1	12.7
3. Trouble getting along with people	1.20	0.93	1.9	24.7	10.4
4. Problems having fun with other people	1.50	1.05	1.4	22.3	20.7
5. Problems participating in hobbies	1.48	1.10	2.2	25.4	23.1
6. Problems making friends	1.49	1.20	1.1	30.4	29.8
7. Problems keeping friends	1.55	1.12	0.8	23.9	26.7
8. Saying inappropriate things	1.23	1.02	2.8	29.2	13.9
9. Complaints from neighbors	0.31	0.72	4.4	80.7	3.7
Risk	0.82	0.53
1. Aggressive driving	1.31	1.12	8.5	32.2	20.2
2. Doing other things while driving	1.59	1.11	8	22.2	28.1
3. Road rage	1.19	1.10	8.5	35.8	17.8
4. Breaking or damaging things	0.59	0.91	1.7	64.4	6.7
5. Doing things that are illegal	0.51	0.85	7.4	67.3	5.1
6. Being involved with the police	0.31	0.67	2.5	78	2.5
7. Smoking cigarettes	1.16	1.26	1.4	46.6	35.7
8. Smoking marijuana	0.58	0.97	1.1	67.4	9.5
9. Drinking alcohol	1.04	0.94	0.8	32.5	9.4
10. Taking “street” drugs	0.33	0.72	1.1	78.6	3.9
11. Sex without protection (birth control, condom)	0.59	0.96	3.3	66.4	8.1
12. Sexually inappropriate behavior	0.28	0.68	6.1	82.4	3.2
13. Being physically aggressive	0.61	0.83	0.6	57.6	4.4
14. Being verbally aggressive	1.36	1.05	0.6	26	18.3

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

External validity

The correlations between the WFIRS-S total score and subdomains scores and EQ-5D scores (EQ-5D descriptive index and VAS score), and the severity of ADHD (CAARS-S:S subscores, WURS-25) and depressive symptoms (BDI-II) are shown in Table 5.

Table 5.

Correlations Between the WFIRS-S Subdomains and Total Scores, and the CAARS-S:S Subdomains, the WURS-25, the BDI, and the EQ-5D Scores.

WFRIS-S Subdomains	CAARS-S:S IMP	CAARS-S:S HR	CAARS-S:S IEL	CAARS-S:S SC	CAARS-S:S Index	WURS-25	BDI	EQ-5D index	EQ-5D VAS
Family	.28**	.23**	.39**	.24**	.40**	.36**	.37**	−.42**	−.35**
Work	.39**	.071	.18**	.24**	.35**	.27**	.29**	−.09	−.16
School	.31**	.22**	.16**	.19**	.33**	.44**	.25**	−.32**	−.42**
Life skills	.42**	.16**	.22	.27**	.39**	.29**	.44**	−.52**	−.56**
Self-concept	.36**	.10	.30**	.54**	.44**	.30**	.59**	−.36**	−.37**
Social activities	.29**	.21**	.29**	.23**	.32**	.38**	.34**	−.34**	−.42**
Risky activities	.087	.23**	.30**	.087	.23**	.41**	.23**	−.29**	−.29**
Total	.45**	.23**	.39**	.36**	.51**	.52**	.53**	−.48**	−.55**

Note. Spearman’s correlation analysis. WFIRS-S = Weiss Functional Impairment Rating Scale–Self-Report; CAARS-S:S = Conners’ Adult ADHD Rating Scales–Self-Report: Short Version; CAARS-S:S IMP = CAARS-S:S impulsivity/emotional lability factor; CAARS-S:S HR = CAARS-S:S hyperactivity/restlessness factor; CAARS-S:S IEL = CAARS-S:S inattention/memory problem factor; CAARS-S:S SC = CAARS-S:S problems with self-concept factor; WURS-25 = Wender Utah Rating Scale; BDI = Beck Depression Index; EQ-5D = EuroQol five-dimension questionnaire; VAS = visual analogue scale.

p < .05. **p < .01.

The negative significant correlations between WFIRS total mean score and EQ-5D measures were high. All WFIRS-S subdomains (except “work” subdomain) showed negative correlations with both EQ-5D VAS and index, ranging from .29 to .56, with the highest negative correlations obtained with the “life skills” subdomain.

The WFIRS-S total mean score showed high positive correlations with the severity of adulthood ADHD symptoms (CAARS-S:S ADHD Index) and depressive symptoms (see Table 5). Each subdomain of the WFIRS-S correlated moderately with the symptoms severity of ADHD (CAARS-S:S Index), except for the “risky activities” subdomain. The “family” subdomain showed moderate correlations with impulsive, emotional lability symptoms. The “work,” “school,” “life skills,” and “self-concept” subdomains showed moderate correlations with inattentive symptoms. The WFIRS-S and the CAARS-S:S “self-concept” subscores were highly correlated. The “risky activities” and “social” WFIRS-S subdomains showed the highest correlation with the impulsive subscore of the CAARS-S:S. Depressive symptoms were positively correlated with all WFIRS-S subdomains, with the strongest association found for the “self-concept” subdomain. The retrospective assessment of the severity of ADHD symptoms in childhood with the WURS-25 also showed a high correlation with the WFIRS-S total mean score, with the “school” and “risky activities” subdomains showing the strongest correlations.

Age was significantly negatively correlated with the “work,” “school,” and “risky activities” subdomains and the total WFIRS-S scores, but the correlation coefficients were small. Despite the absence of association between gender and the WFIRS-S total mean score, male patients showed higher WFIRS-S scores in “self-concept” (male 2.07, SD = 0.77, vs. female 2.35, SD = 0.64; p < .001) and “risky activities” domains (male 0.89, SD = .51, vs. female 0.75, SD = .53; p = .02).

Discussion

The purpose of this study was to confirm the psychometric properties of the WFIRS-S (Canu et al., 2016; Weiss, 2000) and to evaluate its appropriateness for assessing functional impairment in French-speaking adults with ADHD in the context of clinical practice. Overall, our results, obtained in in a large adult ADHD population untreated by psychostimulant, support the construct and internal structural validity as well as the validity of the French adaptation of the WFIRS-S as already reported in its original validation.

The mean scores on each subdomain of the WFIRS-S were above 1.0 (and >0.5 for the “risky activities” subdomain), suggesting a clinically significant functional impairment, and were higher than those obtained in three previous validation studies (Canu et al., 2016; Hadianfard et al., 2017; Takeda et al., 2016). This discrepancy may be related to the originality and the strength of our study, that is, to investigate a large population of untreated adults diagnosed with ADHD according to the gold standard procedure: a structured face-to-face interview on ADHD (DIVA-2; Kooij et al., 2008). This is an important difference with the previous validation studies conducted with samples of 18- to 25-year-old college students (Canu et al., 2016) or 12- to 18-year-old students (Hadianfard et al., 2017). Only the Japanese study included a small sample of adults with ADHD (N = 46), but there were also healthy adults (N = 104) and university students (N = 889; Takeda et al., 2016). Note that the WFIRS-S scores of the present study are consistent with those obtained in previous studies that included patients with an established diagnosis of ADHD, suggesting a similar level of ADHD-related functional impairment across cultural contexts (Hartung et al., 2016; LaCount, Hartung, Shelton, Clapp, & Clapp, 2015).

Thus, the present study is the first to specifically investigate the validity of the WFIRS-S in a rigorously evaluated large sample of adult patients with ADHD and to confirm its value for investigating functional impairments in a clinical setting. Indeed, as our study was conducted in a large population of patients with ADHD, the divergent external validity analyses afford interesting results on the relationship between overall ADHD symptomatology—core symptoms but also comorbid depressive symptoms—and functional impairments. The WFIRS-S total score was moderately related with the severity of ADHD (CAARS-S:S index) and depressive symptoms (BDI-II). These results confirm previous data showing the impact of the severity of core symptoms of ADHD (Stern et al., 2017; Takeda et al., 2016) and of mood symptoms (Anastopoulos et al., 2011; Matthies et al., 2016; Skirrow & Asherson, 2013) on the functional impairments of ADHD.

Moreover, strength of the WFIRS-S is that it investigates several domains of functioning relevant to adults with ADHD. Interestingly, the divergent external validity investigation of this study showed meaningful relationship between specific ADHD core symptoms and specific subdomains of functioning. Inattention core symptoms showed the strongest positive correlation with work impairment, which is consistent with findings on the impact of executive dysfunction in adults with ADHD (Stern et al., 2017). In contrast, hyperactivity symptoms were not strongly associated with functional impairments. Previous studies also found that hyperactivity was a weak predictor of impairment when controlling for inattention and depressive symptoms (Canu et al., 2016; Sibley et al., 2012). Moreover, ADHD-HI is relatively rare in adulthood, as in the present sample (4.1%). Impulsivity core symptoms were mostly associated with work, life skills, and self-concept impairments. Depressive symptoms were mostly associated with family, life skills, self-concept, and social activities impairments. These two findings suggest that externalizing symptoms (such as impulsivity) and internalizing symptoms (such as depressive symptoms), more than inattention or hyperactivity ADHD symptoms, are accurate predictors of a broad range of functional impairments in adults with ADHD (Barkley, Murphy, Dupaul, & Bush, 2002; Richards, Deffenbacher, Rosen, Barkley, & Rodricks, 2006). Finally, self-concept symptoms of the CAARS-S:S were mostly related to the self-concept impairment of the WFIRS-S, while retrospective ADHD core symptoms assessed by the WURS-25 were mostly associated with school impairments, which are two psychometrically very consistent findings. Taken together, these results confirm the value of the multidimensional approach of the WFIRS-S, and demonstrate why it may be used to investigate patients with ADHD beyond a solely symptomatic description of the core symptoms of the disorder.

The psychometric methodology used in the present study was similar to that used in the validation studies in Persian (Hadianfard et al., 2017) and Japanese (Takeda et al., 2016). This transcultural validation supports the structural validity of the instrument, and the present results are consistent with previous findings (Canu et al., 2016; Hadianfard et al., 2017; Takeda et al., 2016; Weiss et al., 2007). Its concurrent external validity explored with the EQ-5D was excellent, which suggests a good relationship between the evaluation of functional impairment with the WFIRS-S and a generic measure of quality of life in adult patients with ADHD. The seven-subdomain structure of the French version was globally confirmed by the CFA and is similar to that in the Persian validation study (Hadianfard et al., 2017). The RMSEA fit index was satisfactory in both the present and Persian studies, but the CFI was weakly acceptable (0.7 in the Persian study, 0.67 in the present study; Hadianfard et al., 2017), in contrast to the Japanese study (CFI = 0.91; Takeda et al., 2016). The fit index of the model was not optimal and items of the “school” subdomains were removed to conduct the analysis. In the Persian study, 12 items were removed from the analysis. Nevertheless, the CFA in that study was not conducted with the original version of the WFIRS-S so it is difficult to compare the psychometric properties of the Persian and French versions. The unsatisfactory CFI in the French version can be related to a weak correlation between the subdomains of the WFIRS-S. As shown in Table 2, the coefficient correlations between the WFIRS subdomains were small to moderate, as in the Persian study (Hadianfard et al., 2017).

Thus, further studies are needed to confirm and strengthen the reliability of the many subdomains of the WFIRS-S. In particular, some subdomains or items could be considered as inappropriate for specific categories of patients (e.g., “school” items for older patients, “work” items for students, some “family” items for individuals living alone, or driving-related items for non-licensed patients). These items were associated with a high rate of “not applicable” responses and could lead to biases in the functional assessment. Moreover, as in the previous validation studies (Canu et al., 2016; Hadianfard et al., 2017; Takeda et al., 2016), the risk subdomain exhibits several items with a floor effect, which questions the utility of some of these items, despite the fact that it is important to screen for rare but potentially clinically significant sources of functional impairment in ADHD. A new method for clustering items may thus be required. Moreover, our results suggest that the WFIRS-S is an appropriate instrument to assess ADHD-related functional impairments in patients referred for a clinical evaluation of ADHD. However, it is quite long and could be inappropriate for patients with cognitive deficits for whom long questionnaires are a challenge. Interestingly, the revised version of the World Health Organization’s classic principles of evaluating scales now highlights the need for equity and access for the entire target population (Andermann, Blancquaert, Beauchamp, & Dery, 2008).

Some limitations need to be addressed. First, test–retest reliability was not assessed. While test–retest intraclass correlation was not evaluated with the original WFIRS-S, it was evaluated in the Persian (Hadianfard et al., 2017) and Japanese (Takeda et al., 2016) studies. Second, we included only stimulant-naive patients, and did not perform comparisons between treated and untreated patients. In the same way, we did not assess the sensitivity to change in a subsample of patients after being evaluated twice, before and after treatment. Third, only a subsample of 97 patients fulfilled the EQ-5D to investigate the concurrent external validation. Fourth, divergent external validity was evaluated with two self-report questionnaires (i.e., CAARS-S:S and WURS-25). We did not use observer ratings (e.g., CAARS observer scales; Conners, Erhardt, & Sparrow, 1999) or investigator assessment, for example, the Adult ADHD Investigator Symptom Rating Scale (Spencer et al., 2010). Furthermore, as a measure of affective symptoms, we used the BDI-II, a self-report assessment of depressive symptomatology. However, recent findings indicated that affective symptoms in ADHD are not limited just to depression but encompass a wide spectrum of emotional traits such as affective lability, emotional overreactivity, and dysregulation (Shaw, Stringaris, Nigg, & Leibenluft, 2014; Skirrow & Asherson, 2013). Further research is needed to evaluate the relationship between functional aspects and these affective symptoms in ADHD using adequate instruments, for example, the Affective Lability Scale (Harvey, Greenberg, & Serper, 1989) or its recent short form (Weibel et al., 2017). Fifth, we did not study functional impairment in relation with other frequent comorbid conditions in ADHD, which include anxiety disorders, substance use disorders, sleep disorders (especially excessive daytime sleepiness), or learning disabilities. Finally, patients were recruited from a single center in a tertiary care university hospital, which might provide a bias toward patients with more severe ADHD symptoms and impairment. Thus, further studies should ideally investigate the validity of the WFIRS-S in a larger population of ADHD patients in primary care. Such studies could encourage the use of the WFIRS-S in diverse health care settings.

In conclusion, the French version of the WFIRS-S is a psychometrically acceptable self-report questionnaire for the multi-domain evaluation of functional impairments in adults with ADHD in a clinical setting. This scale, which precisely measures functioning, should be incorporated into routine clinical evaluation of adults with ADHD. Further work is needed to design a shorter version of the WFIRS-S to provide a simple instrument with new way of assessment (i.e., school vs. work, living alone vs. with family), and good sensitivity to change that can be included systematically in the diagnostic procedure, so that the functional benefits of therapeutic interventions can be measured. The multi-language availability of the WFIRS-S enables further investigations of the functional impact of ADHD in a global perspective by facilitating worldwide epidemiological studies measuring the impact of ADHD over multiple countries.

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.

ORCID iD

Margaret Weiss

Author Biographies

Jean-Arthur Micoulaud-Franchi, MD, PhD, is specialized in psychiatry, neurophysiology, and sleep medicine in the sleep clinic at Bordeaux University Hospital. He received his PhD degree from Aix-Marseille University. His research addresses the link between neurophysiology, sleep, and health perception in mental disorders at the USR CNRS 3413 SANSPY.

Sébastien Weibel, MD, PhD is a psychiatrist specialized in ADHD and mood disorders at Strasbourg’s University Hospital. He received his PhD in neuroscience from Strasbourg University, France. His research interests are currently interaction between ADHD and bipolar disorders.

Margaret Weiss, MD, PhD, is a director of child and adolescent psychiatry at the University of Arkansas for Medical Science. Her research addresses the functional impairment in ADHD.

Marie Gachet, MD, is a psychiatrist specialized in the diagnosis and treatment of adults with ADHD and bipolar disorder at Montpellier’s University Hospital.

Kelly Guichard, MD, is a psychiatrist specialized in sleep disorders and ADHD at Bordeaux’s University Hospital.

Stéphanie Bioulac, MD, PhD, is a psychiatrist specialized in sleep disorders and ADHD at Bordeaux’s University Hospital.

Pierre Philip, MD, PhD, is a psychiatrist specialized in sleep disorders and ADHD at Bordeaux’s University Hospital. He is the head of the sleep disorders Unit, and of the USR CNRS 3413 SANPSY unit. His research adresses the consequences for driving of inattention and sleepiness in ADHD and sleep disorders.

Isabelle Jaussent, PhD, is a methodologist and epidemiologist specialized in sleep disorders. Her research addresses the link between insomnia, sleepiness, and various aspects of aging in the general population.

Yves Dauvilliers, MD, PhD, is the head of the National Reference Center for Narcolepsy and Idiopathic Hypersomnia at the Montpellier’s university hospital. His research addresses the pathophysiology and innovative therapeutics of central disorders of hypersomnolence, and other sleep disorders. He has published several articles and books on these topics.

Régis Lopez, MD, PhD, is a psychiatrist at the adult ADHD outpatient clinic of the Department of Neurology in Montpellier, France. He is also a sleep medicine specialist at the sleep disorders unit in Montpellier, France. He has participated in various researches in the area of ADHD and sleep disorders, including hypersomnias and parasomnias.

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