Adults with ADHD have a high risk of psychiatric comorbidities (Barbaresi et al. 2013; Biederman et al. 2010); however, the existing literature is limited with regard to the differential psychiatric comorbid patterns in individuals who have received treatment compared with those who have not, and in adults with different childhood ADHD subtypes. This study aimed to address these gaps by evaluating the effects of medication and childhood ADHD subtypes on psychiatric comorbidities among adults with ADHD compared with healthy adult controls (Tsai FJ et al. 2019).
The study enrolled 214 adults diagnosed with Diagnostic and Statistical Manual of Mental Disorders – 4th Edition (DSM-IV) ADHD and 145 healthy adult controls aged 18–36 years. Adults with ADHD were screened using the Chinese version of the 6-item Adult ADHD Self-Report Scale v1.1, followed by a telephone interview with a senior researcher. Potential cases with ADHD were then invited for further assessment of the presence of ADHD and other psychiatric disorders using semi-structured psychiatric interviews, intelligence tests and medical records.* Adult healthy controls were screened by telephone interviews to rule out past or current ADHD symptoms, followed by clinical assessments and psychiatric diagnostic interviews to ensure they did not have a lifetime or current diagnosis of ADHD.†
The final study sample included 93 adults with ADHD who had been diagnosed with ADHD during childhood and treated for ADHD, 121 adults with ADHD who had not been treated, and 145 adult controls without ADHD. Results demonstrated that individuals treated for ADHD were more likely to be male compared with drug-naïve individuals and healthy controls. Furthermore, drug-naïve individuals and healthy controls had a higher intelligence quotient and more years of education compared with individuals treated for ADHD. Drug-naïve individuals also experienced more severe inattentive and hyperactive-impulsive (adulthood only) symptoms during childhood and adulthood compared with individuals treated for ADHD. Subsequent analyses performed in the study were controlled to account for these between-group differences.
The psychiatric comorbid patterns by treatment status are summarised below:
- Individuals with ADHD who were drug-naïve were more likely than controls to have psychiatric disorders (odds ratio [OR] 86.08 [95% confidence interval (CI) 37.96–195.17]), including oppositional defiant disorder (ODD; OR 71.50 [95% CI 16.93–301.99]), conduct disorder (CD; OR 22.79 [95% CI 6.83–76.09]), tic disorder (OR 6.44 [95% CI 1.38–29.99]), anxiety disorders (OR 21.62 [95% CI 7.50–62.37]), mood disorders (p < 0.001) such as dysthymic disorder (p < 0.001), substance-use disorders (p < 0.001), sleep disorders (OR 97.99 [95% CI 13.26–723.99]) and eating disorders (p = 0.007).
- Treated individuals with ADHD were also more likely than controls to have psychiatric disorders (OR 26.88 [95% CI 12.63–57.21]), including ODD (OR 69.98 [95% CI 16.36–299.39]), CD (OR, 23.67 [95% CI 6.97–80.33]), tic disorder (OR 8.61 [95% CI 1.84–40.26]), anxiety disorders (OR 14.42 [95% CI 4.85–42.89]), mood disorders (p < 0.001) such as dysthymic disorder (p < 0.001), substance-use disorders (p < 0.001), sleep disorders (OR 47.31 [95% CI 6.26–357.46]) and eating disorders (p = 0.005).
- Compared with controls, drug-naïve individuals were at a higher risk of major depressive disorder (p < 0.001), alcohol-use disorder (p = 0.014) and adjustment disorder (OR 68.49 [95% CI 9.24–507.77]).
- Compared with treated ADHD individuals, drug-naïve individuals were more likely to have generalised anxiety disorder (GAD; OR 4.13 [95% CI 1.51–11.33]), mood disorders (OR 3.24 [95% CI 1.51–6.98]), adjustment disorder (OR 8.37 [95% CI 3.15–22.27]) and sleep disorders (OR 2.07 [95% CI 1.14–3.75]).
The psychiatric comorbid patterns by treatment duration are summarised below:
- Here, drug-naïve individuals with ADHD were at an increased risk of adjustment disorders compared with individuals treated for ADHD for ≤1 year (OR 8.09 [95% CI 1.85–35.38]).
- Drug-naïve individuals with ADHD were at an increased risk of GAD (OR 6.45 [95% CI 1.47–28.41]), mood disorders (OR 10.75 [95% CI 2.48–46.53]) and adjustment disorders (OR 8.56 [95% CI 2.52–29.10]) compared with individuals treated for ADHD for ≥1 year.
- There were no between-group differences in obsessive-compulsive disorder or bipolar disorder across the ADHD groups and controls (p > 0.05).
The psychiatric comorbid patterns by childhood ADHD subtypes are summarised below:
- Participants with childhood combined inattentive and hyperactive-impulsive ADHD (ADHD-C) were more likely to have tic disorder (OR 4.32 [95% CI 1.22–15.21]), panic disorder (OR 2.10 [95% CI 0.41–10.66]) and alcohol-use disorder (p = 0.026) compared with individuals with childhood inattentive ADHD (ADHD-I).
- Participants with childhood ADHD-C were also more likely to have an eating disorder than healthy controls (p = 0.001), and more likely to have ODD (OR 4.76 [95% CI 2.62–8.64]), CD (OR 7.90 [95% CI 3.64–17.13]) and sleep disorders (OR 3.50 [95% CI 1.83–6.68]) than participants with childhood ADHD-I.
- In general, both ADHD subtypes were more likely to have all psychiatric comorbid conditions compared with controls (ADHD-C: OR 115.71 [95% CI 49.19–272.19]; ADHD-I: OR 20.56 [95% CI 9.67–43.70]), with the exception of bipolar disorder (p > 0.05).
- Adults with ADHD-C were more likely to have lifetime ODD (OR 2.25 [95% CI 1.23–4.11]), CD (OR 3.44 [95% CI 1.79–6.62]) and sleep disorders (OR 1.89 [95% CI 1.03–3.49]) compared with adults with ADHD-I.
Multivariate analyses demonstrated that childhood ADHD-C was associated with a higher likelihood of ODD (OR 4.10 [95% CI 2.14–7.85], p < 0.05), CD (OR 7.40 [95% CI 3.21–17.10], p < 0.05) and sleep disorders (OR 4.32 [95% CI 2.14–8.69], p < 0.05). Current use of medication was also associated with a higher risk of anxiety disorders (OR 3.39 [95% CI 1.22–9.41], p < 0.05). Conversely, longer duration of medication use was associated with a lower risk of mood disorders (OR 0.94 [95% CI 0.90–0.99], p < 0.05) and sleep disorders (OR 0.99 [95% CI 0.98–1.00], p < 0.05).
This study was limited by a number of factors. First, the directionality and causality of the significant findings reported here remain to be determined. Second, this study relied on adolescent/mother reports and self-reports regarding childhood ADHD symptoms; although there was a high correlation between these reports, recall bias may still exist. This longitudinal study was also limited as it was not a randomised controlled trial, and could therefore be subject to confounding by indications. Furthermore, the study may be limited by a degree of selection bias, as adults with ADHD were recruited from hospitals through physicians’ referrals and from the community through advertisement.
The authors concluded that these findings suggest that ADHD is associated with high psychiatric comorbidity, which may be reduced by treatment with ADHD medication. Furthermore, childhood ADHD-C is associated with a greater risk of adult comorbidities than ADHD-I. The authors suggested that physicians should consider ADHD medication as a necessary treatment modality to prevent the development of psychiatric comorbid conditions in individuals with ADHD, particularly in children with ADHD-C.
*Diagnostic interviews included the 18-item Conners’ Adult ADHD Diagnostic Interview, the modified adult ADHD supplement of the Chinese version of the Schedule for Affective Disorder and Schizophrenia-Epidemiological Version (K-SADS-E) and SADS. Intelligence tests included the Wechsler Adult Intelligence Scale Revised
†Diagnostic interviews included the 18-item Conners’ Adult ADHD Diagnostic Interview and the modified adult ADHD supplement of the Chinese K-SADS-E. Intelligence tests included the Wechsler Adult Intelligence Scale Revised
Barbaresi WJ, Colligan RC, Weaver AL, et al. Mortality, ADHD, and psychosocial adversity in adults with childhood ADHD: a prospective study. Pediatrics 2013; 131: 637-644.
Biederman J, Petty CR, Monuteaux MC, et al. Adult psychiatric outcomes of girls with attention deficit hyperactivity disorder: 11-year follow-up in a longitudinal case-control study. Am J Psychiatry 2010; 167: 409-417.
Tsai FJ, Tseng WL, Yang LK, et al. Psychiatric comorbid patterns in adults with attention-deficit hyperactivity disorder: treatment effect and subtypes. PLoS One 2019; 14: e0211873.