Recent long-term studies on ADHD onset in childhood and its consequences in adulthood have led to the recognition that ADHD can be a lifetime chronic disorder (Hodgkins et al, 2012), which may impact on quality of life. Despite the growing interest in adult ADHD, until now, its clinical course in adults has been evaluated by only a few studies. The aim of this review was to highlight the clinical and social outcomes among adults diagnosed with ADHD during childhood/adolescence.
In this review, PubMed, PsycINFO and Scopus databases were searched for prospective studies published during the last 5 years assessing adults with ADHD in childhood/adolescence, followed up to adulthood. Studies published before 2015 reported in other reviews with similar outcomes were also included. Three reviewers independently extracted relevant data from the selected studies and two authors independently assessed the risk of bias of the included studies using the Newcastle-Ottawa Scale (NOS). The statistical analyses in the review included calculating the weighted mean with corresponding 95% confidence interval (CI) of investigated outcomes; in particular, percentage of ADHD persistence in adulthood, presence of psychiatric disorders, substance-use disorders (SUDs) and antisocial/criminal activities. The analysis was weighted using the population size of each study, considering the total population or a specific subgroup alternatively.
In total, 39 studies were included in this review for qualitative analysis, and 27 studies, classified as high quality, were included for quantitative analysis. The quality of most studies included in the review was assessed as ‘good’, with a median score of 8 (high quality) according to the NOS score system. The majority of the studies included (28/39) were published after the year 2000 and four research papers were published before 1990. The samples collected by the selected studies were composed of more than 80,000 individuals, with the number of participants ranging between 50 and 73,049. The average mean (standard deviation [SD]) age at baseline was 7.11 (2.5) years and the mean (SD) age at follow-up was 25.65 (5.9) years. One study recruited only females, 11 studies recruited only males and the remaining studies were mainly composed of males.
ADHD persistence data were reported in 20 studies, with a proportion ranging between 5% and 85%, and the persistence of ADHD diagnoses in adulthood was reported by 14 studies, with 12 of these being classified as high quality. Of the 12 high-quality studies, ADHD was found to persist into adulthood with a mean rate of 43% (95% CI 28–58). Furthermore, the prevalence of persistent ADHD in adulthood reported by studies published after 2011 was higher than that reported by studies published between the years 1985–2011 (55% [95% CI 35–76] vs 34% [95% CI 6–62], respectively). Focusing on high-quality studies, persistent ADHD in adulthood was mainly associated with alcohol-use disorder (36% [95% CI 25–48]), antisocial personality disorders (27% [95% CI 11–44]), cannabis use (32% [95% CI 23–41]), SUD (29% [95% CI 18–40]), criminal activities with conviction and/or jail (31% [95% CI 26–36]), and, less frequently, anxiety (27% [95% CI 8–41]) and depressive disorders (21% [95% CI 13–30]). Other psychiatric disorders were reported in comorbidity less frequently, such as bipolar disorders and schizophrenia (12% [95% CI 4–19] and 2.0% [95% CI 1.7–2.2], respectively).
Limitations of this study acknowledged by the authors included that the adopted criteria were not completely standardised, and some relevant studies may have been missed during the selection process, particularly those published before the last 5 years. Despite this, the authors noted that the large number of studies included in this review could confirm the growing interest in this topic during the last 5 years, which has enabled new insight into this disorder.
The authors concluded that this review has contributed towards the ongoing research into long-term consequences of childhood-onset ADHD, confirming that this disorder can persist into adulthood, with a mean rate of 40%. The authors also highlighted that persistent adulthood ADHD was mainly associated with both substance- and alcohol-use disorders, antisocial behaviour, and anxiety and depressive disorders. The wide range of persistence of ADHD observed in this review shows the difficulty in evaluating adult ADHD. The authors suggested that ADHD should be considered as a chronic and complex condition, which can predispose the development of other psychiatric disorders or social maladjustment with detrimental consequences for quality of life in adulthood.
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Di Lorenzo R, Balducci J, Poppi C, et al. Children and adolescents with ADHD followed up to adulthood: a systematic review of long-term outcomes. Acta Neuropsychiatr 2021; Epub ahead of print.
Hodgkins P, Arnold LE, Shaw M, et al. A systematic review of global publication trends regarding long-term outcomes of ADHD. Front Psychiatry 2012; 2: 84.