Prevalence and correlates of adult attention-deficit hyperactivity disorder: meta-analysis
- SIMON Viktoria, CZOBOR Pal, BALINT Sara
- Journal article citation:
- British Journal of Psychiatry, 194(3), March 2009, pp.204-211.
- Cambridge University Press
In spite of the growing literature about adult attention-deficit hyperactivity disorder (ADHD), relatively little is known about the prevalence and correlates of this disorder. This study aimed to estimate the prevalence of adult ADHD and to identify its demographic correlates using meta-regression analysis. Searches were conducted using the MEDLINE, PsycLit and EMBASE databases as well as hand-searching to find relevant publications. The pooled prevalence of adult ADHD was 2.5% (95% CI 2.1–3.1). Gender and mean age, interacting with each other, were significantly related to prevalence of ADHD. Meta-regression analysis indicated that the proportion of participants with ADHD decreased with age when men and women were equally represented in the sample. Prevalence of ADHD in adults declines with age in the general population. It is thought, however, that the unclear validity of DSM–IV diagnostic criteria for this condition can lead to reduced prevalence rates by underestimation of the prevalence of adult ADHD.
- Extended abstract:
SIMON Viktoria; CZOBOR Pal; BALINT Agnes; et al;
Prevalence and correlates of adult attention-deficit hyperactivity disorder: meta-analysis.
Journal citation/publication details
British Journal of Psychiatry, 194(3), March 2009, pp.204-211.
Six studies are reviewed, and deliver a pooled prevalence rate for adult attention deficit hyperactivity disorder (ADHD) of 2.5%, somewhat lower than the results of several individual studies. This is possibly a result of the inability of DSM-IV diagnostic criteria to detect adult ADHD accurately. Meta-regression analyses indicate that the prevalence of ADHD declines with age where men predominate in samples, but increases when women predominate. However, the latter finding may occur because women who were undiagnosed in childhood are referred for assessment in adulthood as the result of of comorbid disorders.
ADHD is now thought to persist into adulthood in a high proportion of cases, and studies indicate structural and functional brain abnormalities. ADHD is a serious risk factor for comorbid psychiatric disorders, functional impairments and poor socio-economic outcomes, but relatively little is known about adult prevalence.
What sources were used?
EMBASE (Excerpta Medica), Medline and PsycINFO were searched. The reference lists of relevant studies were also checked.
What search terms/strategies were used?
The search strategy was: (adult AND ADHD) AND (epidemiology OR prevalence).
What criteria were used to decide on which studies to include?
No inclusion criteria are reported beyond those implied by the search terms. Studies involving special populations (e.g. those in prison, drug addicts) were excluded, together with those that did not report sufficient data for meta-analysis.
Who decided on their relevance and quality?
This is not reported.
How many studies were included and where were they from?
Six population-based studies were included, with summary details of sample size, age and gender in Table 1, and of study design and source of diagnostic data in Table 2. Geographical origins are not reported but include several different countries. Six further population-based studies are noted in the text but excluded for a variety of reasons.
How were the study findings combined?
The prevalence of ADHD in adulthood was estimated using a mixed-effect (with fixed and random effects) meta-regression based on a general linear mixed-model technique using the approximate likelihood approach developed by van Houwelingen et al.
Findings of the review
Most of the six studies were based on large numbers of participants but most of these were ‘samples of convenience, which do not assure representativeness.’ Ages were generally low, ranging from 19.4 to 28.5 for most samples (overall mean 34 years). Gender proportions ‘were neither balanced nor representative of the target population’. All studies used the DSM-IV diagnostic criteria, although all questioned its validity when applied to adults.
The pooled prevalence of ADHD across the samples was 2.5%. Prevalence ‘has a significant negative association with age, although this association is moderated by the gender composition of the sample’: prevalence declines with age when samples are more than half male, and increases with age when less than a third male. This might partly be the result of ‘pseudo-new’ cases in which women who were not diagnosed in childhood because they did not present with disruptive behaviour at that time are referred in adulthood because of comorbid disease.
The pooled prevalence rate ‘seems to be conservative’ when compared with some of the published prevalence estimates (1%-7.3%) in the six reviewed studies and six additional population-based studies that were excluded from review and did not necessarily use DSM-IV diagnostic criteria. This may be because people with ADHD ‘outgrow the diagnostic criteria’: while functional impairment and low socio-economic outcomes are still detected, symptoms appear to be reduced.
‘In summary, we think that our finding is consistent with the suggestion that the prevalence of ADHD declines with age; however, the background of this phenomenon remains unclear and a caveat is needed in this regard. Specifically, the validity of the DSM-IV diagnostic criteria for diagnosing adult ADHD is an important issue, emerging both from the interpretation of our findings and also from the relevant literature.’ Using strict DSM-IV criteria may lead to an under-estimation of prevalence, and further work is needed to clarify how far the observed changes in prevalence are the result of natural development or of methodological issues.
Implications for policy or practiceNone are discussed
- Subject terms:
- ADHD, adults, gender;
- Content type:
- research review
Register/Log in to view this article
Journal home page
- ISSN online:
- ISSN print: