February 18, 2025
Background:
ADHD is commonly accompanied by psychiatric comorbidities that complicate its diagnosis and treatment. Roughly two out of three affected children and adolescents have one or more comorbid psychiatric disorder.
Because the peak age of ADHD onset is typically a decade or more earlier than those for schizophrenia, depressive disorder, or bipolar disorder, it is essential to explore these comorbidities over an extended period. Populations studies help researchers identify broader patterns and trends within an entire population and includes adults as well as children. This type of study provides unique insights into the population at large, rather than a sample group.
In earlier studies the maximum follow-up period was twelve years, insufficient in view of the roughly ten years between onset of ADHD and onset of major psychiatric disorders. Also, previous nationwide population studies have included less than 150,000 participants.
This study, relying on data from South Korea’s universal single-payer health insurance system, included over one and a half million individuals. Persons previously diagnosed with depression, bipolar disorder, tic disorder, or schizophrenia were excluded.
382,434 individuals had been diagnosed with ADHD, while 1,169,279 were without an ADHD diagnosis.
Propensity score matching ensured that potential confounders, both sociodemographic and clinical, were equalized for the ADHD and control groups. After matching, there were 353,898 individuals in each group.
After these adjustments, individuals in the ADHD group were at least an order of magnitude more likely to subsequently be diagnosed with psychiatric disorders than their peers without an ADHD diagnosis:
Conclusion:
The Korean study team concluded, “Overall, our findings suggest that upon prolonged examination, the risk of subsequent diagnoses of other psychiatric disorders in individuals with ADHD appears to be higher than that reported previously. … Therefore, patients with ADHD should be carefully screened for the presence of other psychiatric symptoms on a regular basis from an earlier age … It is advisable to have a follow-up period extending beyond 10 years to sufficiently identify the occurrence of comorbid disorders in patients with ADHD.”
Sujin Kim, Mi-Sook Kim, Jinhee Kim, Jae Sung Kim, and Soon-Beom Hong, “Attention-deficit/hyperactivity disorder and subsequent diagnoses of major psychiatric disorders: a nationwide population-based study,” European Child & Adolescent Psychiatry, https://doi.org/10.1007/s00787-024-02497-5.