A groundbreaking study has revealed that many mental health conditions may share more genetic similarities than previously thought. Researchers from the University of Colorado Boulder and Mass General Brigham analyzed DNA from over six million individuals, including more than one million diagnosed with at least one psychiatric disorder. This extensive research could significantly change how mental health conditions are diagnosed and treated, particularly for those living with multiple diagnoses.
The World Health Organization estimates that over a billion people worldwide are affected by mental health conditions. Current diagnostic practices rely heavily on observable symptoms, leading to complex cases where individuals receive multiple diagnoses. “Right now, we diagnose psychiatric disorders based on what we see in the room, and many people will be diagnosed with multiple disorders,” explained Andrew Grotzinger, assistant professor of psychology and neuroscience at the University of Colorado Boulder and corresponding author of the study. “That can be hard to treat and disheartening for patients.”
Shared Genetic Patterns Across Disorders
The research examined 14 different psychiatric disorders and identified that most genetic differences could be attributed to just five broad genetic patterns. These patterns are associated with 238 genetic variants affecting brain development and function. Based on these findings, the researchers categorized the conditions into five groups: disorders with compulsive traits such as anorexia nervosa and obsessive-compulsive disorder, internalizing conditions including depression and anxiety, substance use disorders, neurodevelopmental conditions like autism and attention-deficit hyperactivity disorder, and the fifth group encompassing bipolar disorder and schizophrenia.
Remarkably, around 70 percent of the genetic signals linked to schizophrenia were also found to be associated with bipolar disorder. Traditionally regarded as distinct illnesses, these two conditions may actually share a closer genetic relationship than previously understood. “Genetically, we saw that they are more similar than they are unique,” Grotzinger noted.
The findings, published in the journal Nature, challenge the long-standing belief that mental health disorders are largely separate illnesses. Instead, the study suggests that many conditions may be driven by shared biological processes.
Implications for Future Research and Treatment
While the findings are promising, the research team cautions against immediate changes to current diagnostic practices. They aim to inform future revisions of the Diagnostic and Statistical Manual of Mental Disorders, the globally recognized handbook for mental health professionals. “This work provides the best evidence yet that there may be things that we are currently giving different names to that are actually driven by the same biological processes,” Grotzinger stated.
By identifying commonalities across various disorders, the researchers hope to develop treatment strategies that do not require multiple medications or different psychotherapeutic interventions for each diagnosis.
The study also spotlighted specific biological pathways linked to different groups of mental health conditions. For instance, genes impacting excitatory neurons, which transmit signals in the brain, were more pronounced in individuals with bipolar disorder and schizophrenia. In contrast, genetic variants associated with oligodendrocytes—cells that maintain and protect the brain’s wiring—were more prevalent in those suffering from depression and anxiety.
Some of these shared genetic factors appear to influence brain development early in life, even before birth, while others may have a greater impact in adulthood. This could help elucidate the frequent overlap of mental health conditions. A 2018 review indicated that over half of individuals diagnosed with one psychiatric disorder later receive additional diagnoses, with around 41 percent meeting criteria for four or more conditions throughout their lives.
As the field of mental health research continues to evolve, this study could pave the way for a more integrated understanding of psychiatric disorders, ultimately leading to better care and outcomes for millions worldwide.
