For decades, scientists have treated conditions like depression, ADHD, and schizophrenia as separate illnesses. Still, new research suggests they may be connected at a much deeper level, by the same genes influencing brain development.
A US study published in Cell found that eight major psychiatric disorders, including autism, bipolar disorder, obsessive-compulsive disorder, and anorexia, share a common genetic foundation. Let’s look at what the researchers discovered, how these shared variants might shape the brain, and why this could change how we think about mental health treatments in the future.
The shared genetic roots of mental illness
Researchers from the University of North Carolina analyzed nearly 18,000 genetic variations linked to eight psychiatric disorders. They identified 683 variants that influenced how genes are regulated inside brain cells, changes that can affect how neurons form and function over time.
These shared variants, known as pleiotropic genes, appear to play a much bigger role than previously thought. Rather than being tied to one condition, they’re active in multiple stages of brain development and in different types of brain cells. That means the same genetic mechanisms may increase the risk for several mental health conditions at once.
“Changes to these proteins in particular could ripple through the network, potentially causing widespread effects on the brain”, explained geneticist Hyejung Won, who led the study. Her team found that these pleiotropic genes are highly connected to other proteins in the brain, forming complex networks that influence how neurons grow, communicate, and mature.
The study helps explain why conditions like autism and ADHD often occur together, and why mental illnesses frequently run in families. Earlier research had already shown overlap among 109 genes linked to various disorders, but this study goes further by showing how those shared genes actually behave during brain development.
By observing how the genetic variants operated inside developing neurons—both human and mouse cells—the researchers revealed that these shared genes remain active far longer than previously known. This extended activity may make the brain more vulnerable to disruptions that manifest differently depending on other genetic or environmental factors.
What shared genetics mean for mental health treatment
Pleiotropy—the idea that one gene can influence multiple traits—was once seen as a complication in psychiatry. It blurred diagnostic lines and made disorders harder to define. But according to Won, it could be the key to better treatment.
“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“, she said.
In other words, instead of developing separate drugs for each condition, researchers could target the shared biological pathways underlying them all. This approach might one day allow doctors to treat depression, schizophrenia, or anxiety by focusing on the same cellular systems that tie them together.
Given that nearly one in eight people worldwide lives with a mental health disorder, this genetic overlap could have major clinical implications. Understanding how these shared genes shape the brain may lead to earlier diagnosis, better treatment precision, and a clearer picture of how mental illness develops.