Psychiatric comorbidity appears to play a key role in an elevated risk of premature death in adults with attention-deficit/hyperactivity disorder (ADHD), according to a longitudinal study published online in JAMA Psychiatry.
“In a national register-based cohort study with more than 2.6 million individuals, we found that ADHD was associated with elevated all-cause and cause-specific mortality risks,” researchers reported. “The association was stronger in adulthood than in childhood, with increased risks when ADHD was diagnosed later.”
“In adulthood, the all-cause mortality risk increased substantially with the number of psychiatric comorbidities with ADHD,” they wrote.
The study was based on Swedish national register data for people born between 1983 and 2009, 3.2% of whom were diagnosed with ADHD.
Among individuals with ADHD, 424 died during follow-up, compared with 6231 deaths in the group without ADHD. That translated to an all-cause mortality rate of 11.57 per 10,000 person-years for people with ADHD compared with a mortality rate of 2.16 per 10,000 person-years for people without ADHD.
While the adjusted hazard ratio of all-cause mortality with ADHD alone was 1.41, it increased substantially with the number of psychiatric comorbidities, the study found. With a single comorbid psychiatric condition, the hazard ratio of all-cause mortality was 3.71; with 4 or more psychiatric comorbidities, it was 25.22.
Among adults, early-onset psychiatric comorbidity was primarily associated with deaths due to natural causes, such as neoplasms, researchers found. Later-onset psychiatric comorbidity—substance use disorder, in particular—was mainly associated with deaths from unnatural causes, such as suicide and unintentional injury.
“These findings suggest that health care professionals should closely monitor specific psychiatric comorbidities in individuals with ADHD to identify high-risk groups for prevention efforts,” researchers advised.
Sun S, Kuja-Halkola R, Faraone SV, et al. Association of psychiatric comorbidity with the risk of premature death among children and adults with attention-deficit/hyperactivity disorder. JAMA Psychiatry. 2019 August 7;[Epub ahead of print].