The World Health Organization Adult ADHD Self-Report Scale (ASRS) was developed to estimate the prevalence of ADHD in adults. A summary index of the 18-item (e.g. Diagnostic and Statistical Manual of Mental Disorders – 4th Edition symptoms of inattention and hyperactivity-impulsivity) version of the scale showed good discriminant validity that was in agreement with the clinicians’ diagnoses. A shorter version of the scale with only 6 items (ASRS-6) showed better discriminant validity compared with the 18-item ASRS, but was only in moderate agreement with clinical diagnoses of ADHD. Various studies have reported differences in the prevalence of ADHD in population-based samples where estimates range between 1.2% and 7.3%. The aim of this study was to assess the convergent and discriminant validity of ASRS-6 compared with the 18-item ASRS in a general population sample, examining the psychometric properties in separate age groups.
Data from the 2014 wave of the Stockholm Public Health Cohort, which comprised participants (n=50,157; aged 18–84 years; 70.5% participation rate) contacted between 2002 and 2010 by postal questionnaire in the Stockholm County, were used in this study. Each ASRS item of inattention and hyperactivity-impulsivity has five response categories, scored from 0 to 4: “never”, “rarely”, “sometimes”, “often” and “very often”. In this study, summary indexes of the Lickert-type score responses were computed for participants who replied to all 6 items on the ASRS-6 (potential score range: 0–24). A score of ≥4 on the 0–6 scale (sensitivity 39.1; specificity 88.3) and ≥14 on the 0–24 scale (sensitivity 64.9; specificity 94.0) indicated a positive diagnosis for ADHD. Details regarding age, gender, country of birth, marital status, income, highest level of education, substance use and alcohol consumption were also obtained. Age was classified as young early adulthood (22–29 years), early adulthood (30–44 years), adulthood (45–64 years) and mature (≥65 years). Item response theory (IRT) was used to assess convergent validity, and discriminant validity was determined using the correlation between the ASRS and known correlates.
The overall prevalence of ADHD among participants across score range groups was: 0–9 = 80.3%; 10–13 = 14.8%; 14–17 = 3.9%; and 18–24 = 1.0%. In the shorter 6-item version of the ASRS, the prevalence of ADHD among participants was: 0–1 = 72.1%; 2–3 = 21.1%; and 4–6 = 6.8%. Severity of the items, measured using IRT, on the ASRS-6 ranged from 0.9–2.9 in the entire cohort, with moderate discrimination found for the two hyperactivity-impulsivity items and one of the inattention items. Low discriminatory ability was shown for the inattention items across all age ranges. Measures of autism, psychosocial stress, education, substance use and heavy alcohol consumption, but not income or education, significantly correlated with the ASRS.
The lack of a clinical ADHD interview was a limitation of this study, and since the sensitivity and specificity of the 18-item ASRS (which was used as the reference index) is unknown, it remains unclear whether the estimated prevalence using ASRS-6 reflects the true population prevalence of ADHD.
The authors concluded that validity tests of the ASRS-6 indicate that this shortened scale is appropriate for measuring the incidence of ADHD in the general population, with a prevalence of 4.9% with the 18-item ASRS scale and 6.8% using the ASRS-6 scale, which is in line with previous reports of 4% and 1–7% in public mental health surveys.
Read more about the ASRS-6 here
Lundin A, Kosidou K, Dalman C. Testing the discriminant and convergent validity of the World Health Organization six-item adult ADHD self-report scale screener using the Stockholm Public Health Cohort. J Atten Disord; Epub ahead of print