ADHD positively associated with suicidal behaviour

Individuals with attention-deficit hyperactivity disorder (ADHD) are likely to exhibit suicidal behaviour, and this probability is further increased in the presence of comorbid psychiatric disorders, a recent study suggests.

The study used nationwide registers covering the entire population of Denmark, including 2.9 million individuals followed for more than 46 million person-years. A total of 37,705 suicidal events (4,930 suicide deaths; 32,775 suicide attempts) were documented during the 20 years of observation.

ADHD was diagnosed in 32,540 individuals (including 10,019 females). This group was followed for 164,113 person-years and 697 suicidal outcomes (35 suicide deaths; 662 suicide attempts) were recorded. The incidence rates of suicidal behaviour in the total cohort and those with ADHD were 75.5 and 415.6 per 100,000 person-years, respectively.

The incidence rate ratio (IRR) of suicidal behaviour was 4.7 (95 percent CI, 4.3–5.1) in the ADHD vs the non-ADHD group. The rate was 3.4-fold (3.04–3.76) higher in males and 9.1-fold (8.12–10.12) higher in females relative to their counterparts without ADHD.

For persons with ADHD and comorbid disorders, the IRR was even higher at 10.4 (9.5–11.4). Having an increasing number of different comorbid disorders was associated with increasing rates of suicidal behaviour. Specifically, individuals having one, two, and three or more comorbid disorders had IRRs of 4.76 (3.88–5.84), 4.41 (3.47–5.61) and 8.20 (7.36–9.13), respectively, as compared with those without ADHD.

The findings point to people with ADHD and comorbid psychiatric disorders as targets for suicide preventive interventions, researchers said. Clinicians might consider other risk factors, such as juvenile delinquency and/or a history of psychiatric disorders or suicidal behaviour in parents, when evaluating risk of suicidal behaviour.