The largest and most comprehensive study to date finds substantial genetic overlap across 14 psychiatric conditions, with internalizing and substance-use disorders sharing notable genetic risk and shaping potential treatment directions.

Internalizing disorders (including major depressive disorder, anxiety, and PTSD) and substance use disorders, along with ADHD and related conditions, show the strongest shared genetic risk, while schizophrenia and bipolar disorder share a substantial, yet distinct, overlap.

Disorders with shared genetic risk cluster into five groups: compulsive disorders; internalizing disorders; neurodevelopmental disorders; schizophrenia and bipolar disorder; and substance-use disorders, reflecting organized genetic architecture across conditions.

Biological patterns align with these genetic overlaps, such that internalizing disorders show oligodendrocyte-related gene enrichment and schizophrenia/bipolar disorders link to excitatory neuron–related genes.

Researchers identified 428 genetic variants linked to multiple disorders and 101 chromosomal regions with high concentrations of shared variants, underscoring widespread pleiotropy.

The analysis draws on a large international dataset spanning more than six million individuals, underscoring the scale and robustness of the findings.

The study is described as the largest and most comprehensive assessment of genetic overlap among these 14 conditions, with implications for understanding biology and guiding more tailored treatments.

ADHD and autism spectrum disorder show a strong genetic correlation, indicating shared risk factors, with a 2025 study linking later-diagnosed autism with ADHD and other conditions more than early-diagnosed autism.

Co-occurring disorders are common: about half of individuals with one psychiatric disorder may receive a second or third diagnosis, with anxiety and depression frequently accompanying ADHD.

Cited context notes that anxiety, depression, and other conditions often co-occur with ADHD, highlighting the real-world complexity of clinical presentations.

Cited sources include Nature and related autism prevalence studies, along with prior DSM-based prevalence research, situating the findings within established literature.

Overall, the findings point toward a shared genetic scaffold across conditions that could inform more integrated screening and intervention strategies.