Genetic Overlap in Psychiatric Disorders: A New Frontier in Mental Health
Recent research has unveiled a significant genetic overlap among eight major psychiatric disorders, shedding light on the complex interplay between genetics and mental health.
Researchers have long observed that disorders such as autism, ADHD, schizophrenia, bipolar disorder, major depressive disorder, Tourette syndrome, obsessive-compulsive disorder, and anorexia nervosa frequently co-occur. Still, the underlying genetic connections were not fully understood.
This groundbreaking discovery deepens our understanding of psychiatric conditions and opens new doors for targeted treatments that address multiple disorders simultaneously.
Shared Genetic Basis of Psychiatric Disorders
In 2019, an international team of researchers identified 109 genes that are associated with a spectrum of psychiatric conditions, including:
Autism spectrum disorder (ASD)
Attention-deficit/hyperactivity disorder (ADHD)
Schizophrenia
Bipolar disorder
Major depressive disorder (MDD)
Tourette syndrome
Obsessive-compulsive disorder (OCD)
Anorexia nervosa
This shared genetic foundation may explain why many psychiatric conditions exhibit overlapping symptoms and frequently co-occur within individuals and families. For example, up to 70% of people with autism also have ADHD, highlighting a genetic and neurodevelopmental link between these conditions.
New Insights into Shared Genetic Variants
A recent study published in Cell explored these shared genetic variants in greater depth to understand their function and potential as therapeutic targets. Researchers identified 683 genetic variants that influence gene regulation during brain development.
Notably, they found that these genetic variants are active for extended periods during brain development, suggesting they may impact multiple neurodevelopmental processes. This discovery challenges the traditional view that psychiatric disorders are entirely distinct entities and supports the idea that they may arise from common genetic pathways.
Pleiotropy: A Key Factor in Psychiatric Genetics
Many of these genetic variants exhibit pleiotropy, meaning they influence multiple traits or disorders. The pleiotropic genes involved in psychiatric conditions were found to:
Play a role in multiple stages of brain development
Be highly interconnected with other proteins, meaning that changes in one gene could create ripple effects throughout neural networks
Participate in complex gene regulation mechanisms, potentially affecting how neurons develop and function
Because these shared genetic factors influence multiple psychiatric disorders, understanding their mechanisms could pave the way for treatments that address multiple conditions simultaneously.
How Do These Genetic Variants Affect Brain Development?
The study used advanced gene-editing techniques, inserting nearly 18,000 genetic variations into precursor cells that develop into neurones. This allowed researchers to observe how these variants influenced gene expression and neural development in real-time.
Key insights from the study include:
Impact on protein interactions: Shared genetic variants were involved in many more protein-to-protein interactions than unique gene variants, indicating a more significant influence on brain function.
Gene regulation mechanisms: These variants affect crucial regulatory processes that control brain development, suggesting they contribute to a cascade of effects rather than isolated disruptions.
Broad activity across different brain cells: Unlike condition-specific genes, pleiotropic variants were active in multiple types of brain cells, further explaining their wide-ranging impact on mental health.
The Link Between Psychiatric Disorders: Why Do They Overlap?
Many psychiatric conditions share similar symptoms and frequently co-exist in individuals, a phenomenon long observed in clinical psychology. For example:
Bipolar disorder and schizophrenia share genetic risk factors, which is why some symptoms, such as mood instability and psychosis, can appear in both conditions.
Obsessive-compulsive disorder (OCD) and Tourette syndrome are strongly linked, with overlapping genetic components influencing compulsive behaviours and tics.
These findings suggest that psychiatric disorders should not always be viewed as entirely separate conditions but rather as different manifestations of shared neurodevelopmental pathways.
Potential for Novel Psychiatric Treatments
The ability to target shared genetic factors across multiple psychiatric disorders presents an exciting opportunity for precision medicine. Instead of treating each disorder separately, future therapies could focus on common genetic pathways, potentially benefiting a broader range of patients.
Dr Hyejung Won, a geneticist from the University of North Carolina, explains:
"If we can understand the genetic basis of pleiotropy, it might allow us to develop treatments targeting these shared genetic factors, which could then help treat multiple psychiatric disorders with a common therapy."
Given that nearly 1 in 8 people worldwide live with some form of psychiatric condition, according to the World Health Organization (WHO), the implications of this research are profound. Targeted therapies could revolutionise mental health treatment, offering hope to millions who struggle with multiple psychiatric disorders.
Future Directions in Genetic Psychiatry
The next steps in psychiatric genetics research will likely focus on:
Identifying specific pathways through which these genetic variants influence brain development and function
Developing precision medicine approaches to target shared genetic mechanisms
Expanding research into gene-environment interactions, as environmental factors can also shape psychiatric outcomes
By integrating genetic insights with advances in neuroscience and pharmacology, we may be on the verge of a new era in mental health treatment, where a single targeted therapy could address multiple psychiatric conditions at their root cause.
This breakthrough research on shared genetic variants among psychiatric disorders underscores the interconnected nature of mental health conditions. By shifting the focus from isolated disorders to common genetic mechanisms, scientists are paving the way for more effective, personalised treatments. With continued advancements in genomic medicine, neurobiology, and pharmacogenetics, the future of mental health care could see more precise, multi-condition treatments that improve the lives of millions worldwide.
Original Study:
Lee, S. Jiseok, JC. McAfee, M. et al. (2025). Massively parallel reporter assay investigates shared genetic variants of eight psychiatric disorders. Cell. doi:10.1016/j.cell.2024.12.022
References:
World Health Organization. "Mental health: Strengthening our response." Retrieved 2025.
University of North Carolina Research Institute, "Genetic basis of psychiatric disorder pleiotropy," 2025.