Scientists Uncover Genetic Links Between Eight Major Psychiatric Disorders

Eight psychiatric conditions that appear very different on the surface may share important genetic influences beneath the brain’s complex biology. New research suggests that genetic variations affecting brain development could help explain why conditions such as ADHD, autism, schizophrenia, and anorexia sometimes occur together.

The findings could eventually help scientists develop treatments that target biological mechanisms shared by multiple disorders. However, researchers still have considerable work ahead before these discoveries can be translated into clinical care.

Scientists Find Genetic Variants Connected To Eight Disorders

A study published in the journal Cell in 2025 examined genetic variations associated with eight psychiatric conditions. Led by University of North Carolina geneticist Hyejung Won and her colleagues, the research investigated how these variants influence gene regulation in developing brain cells.

The researchers examined 17,841 genetic variants located within regions of the genome previously associated with psychiatric disorders. Using human neuronal precursor cells, which develop into neurons, they identified 683 variants that affected gene regulation. The team then investigated how these variants behaved in developing neurons, including experiments involving mouse cells.

The results revealed differences between genetic variants associated with multiple psychiatric conditions and those linked more specifically to individual disorders. Variants shared across several conditions tended to influence more protein interactions and operate across a wider range of brain cell types.

Some of these shared variants also remained active across multiple stages of development. This could help explain how genetic differences influence biological processes involved in more than one psychiatric condition.

The researchers believe these findings could eventually help identify new treatment targets. However, the study does not establish that all eight disorders have one single cause. Instead, it provides evidence that some genetic influences overlap, even when the conditions have different symptoms and diagnostic criteria.

Which Eight Psychiatric Conditions Share Genetic Influences?

The Cell study focused on eight conditions with previously identified genetic connections. Although each condition has its own diagnostic characteristics, researchers have found that some of their underlying genetic influences overlap.

The conditions examined were autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, bipolar disorder, major depressive disorder, Tourette syndrome, obsessive-compulsive disorder (OCD), and anorexia nervosa.

Autism can affect social communication and involve restricted interests or repetitive behaviors. ADHD is associated with persistent patterns of inattention, hyperactivity, and impulsivity. Both are classified as neurodevelopmental conditions, although their characteristics and effects on daily life vary considerably.

Schizophrenia can affect perception, thinking, emotions, and a person’s understanding of reality. Bipolar disorder involves episodes of depression and mania or hypomania, while major depressive disorder can cause persistent low mood or loss of interest that interferes with everyday activities.

Tourette syndrome involves multiple motor tics and at least one vocal tic. OCD is characterized by intrusive, unwanted thoughts and repetitive behaviors or mental rituals. Anorexia nervosa is an eating disorder associated with restricted food intake, intense concerns about weight or body shape, and potentially serious health consequences.

These conditions are not interchangeable, and people diagnosed with the same disorder can have very different experiences. Shared genetic influences help explain some biological overlap, but they do not eliminate the differences between individual diagnoses.

How Genetic Variations Can Affect Brain Development

Genes contain instructions that help cells function, grow, and maintain their biological processes. Gene regulation determines when particular genes become active and how much of their products cells produce.

Changes in this regulation can affect the development and operation of the brain. Their consequences depend partly on the type of cell involved, the stage of development, and the other biological processes connected to the affected genes.

The researchers investigated how genetic variants influenced gene regulation in neuronal precursor cells. These cells eventually develop into neurons, which transmit information throughout the nervous system.

By testing thousands of genetic variants, the team identified hundreds that altered gene regulation. This allowed the researchers to investigate which variants were shared across disorders and which were more specific to individual conditions.

What Scientists Mean By Pleiotropy

The study focused on a phenomenon known as pleiotropy. It occurs when a single genetic factor influences multiple traits or outcomes.

In psychiatric genetics, a variant associated with more than one disorder can be described as pleiotropic. The same genetic variation may influence biological processes involved in different conditions, although its effects can differ depending on the circumstances.

The researchers found that these shared variants were more interconnected with other proteins than variants associated with individual disorders. They also affected a broader range of brain cell types and showed activity across multiple developmental stages.

As Won explained, “The proteins produced by these genes are also highly connected to other proteins.”

She added that changes to these proteins could ripple through the network, potentially producing widespread effects on the brain.

This interconnected activity offers one possible explanation for why a genetic variation can influence several psychiatric conditions. A change affecting one biological process may also influence other processes connected to it.

However, a shared genetic variant does not automatically cause multiple disorders. Psychiatric risk generally involves many genetic influences alongside environmental and developmental factors. The researchers are investigating one part of that complex relationship.

Why Psychiatric Disorders Frequently Occur Together

Psychiatric conditions sometimes overlap in the same person. Someone diagnosed with ADHD, for example, may also experience depression or anxiety, while some people with autism have additional psychiatric diagnoses.

Shared genetic influences could help explain part of this pattern. If different conditions involve some of the same biological processes, the genetic factors contributing to vulnerability may overlap as well.

Earlier research published in 2019 identified 109 genes linked in different combinations to the eight conditions examined in the Cell study. That work helped establish the genetic connections that researchers subsequently investigated in greater detail.

The 2025 findings add information about how variants within these shared regions behave. Researchers found that shared variants could affect gene regulation across different cell types and developmental stages, potentially influencing multiple biological pathways.

Psychiatric diagnoses are primarily based on clinical symptoms and established diagnostic criteria. Those criteria remain important because two people with overlapping genetic risk can experience different symptoms, levels of impairment, and treatment needs.

A clearer understanding of shared genetic influences could eventually complement clinical assessments. It may also help explain why some people develop multiple psychiatric conditions during their lives.

A Separate Study Found Five Broad Genetic Patterns

A different study published in Nature investigated genetic similarities across a wider range of psychiatric disorders. Led by researchers from the University of Colorado Boulder and Mass General Brigham, the study examined DNA data from more than one million people diagnosed with at least one of 14 psychiatric disorders, alongside data from five million people without those diagnoses.

The researchers identified five broad genomic factors involving 238 genetic variants. These factors captured much of the genetic variation distinguishing people with particular diagnoses from those without them.

The analysis grouped several disorders according to shared genetic patterns. These included internalizing conditions such as depression and anxiety, neurodevelopmental conditions such as autism and ADHD, and disorders involving compulsive features.

The study also found substantial genetic overlap between schizophrenia and bipolar disorder. Approximately 70% of the genetic signal associated with schizophrenia was also associated with bipolar disorder, according to the researchers.

“Genetically, we saw that they are more similar than they are unique,” said Andrew Grotzinger, an assistant professor of psychology and neuroscience at the University of Colorado Boulder and a corresponding author of the study.

The finding challenges the idea that psychiatric diagnoses always correspond to entirely separate biological categories. Nevertheless, the researchers cautioned that the evidence does not justify combining existing diagnoses at this stage.

What The Two Studies Tell Scientists

The Cell and Nature studies used different methods and examined different aspects of psychiatric genetics. The Cell research investigated the functional effects of specific genetic variants associated with eight conditions, while the Nature study examined broad genetic patterns across 14 disorders.

Together, the findings provide complementary evidence that psychiatric conditions can share biological foundations. They also suggest that studying the relationships between diagnoses could reveal information that researchers might miss when examining each condition separately.

Neither study demonstrates that all psychiatric disorders arise from one genetic mechanism. Instead, both point toward a more complicated picture involving overlapping genetic influences and distinct biological processes.

Could Shared Genetic Findings Lead To New Treatments?

One of the most significant possibilities raised by the research is that treatments targeting shared biological mechanisms could eventually help people with multiple psychiatric conditions.

Current psychiatric care frequently involves selecting treatments according to a person’s symptoms, diagnosis, and individual circumstances. When several conditions occur together, clinicians may need to address different sets of symptoms and treatment needs.

A better understanding of shared genetic influences could help researchers identify biological pathways contributing to multiple disorders. Those pathways might eventually become targets for therapies designed to address more than one condition.

Won explained that pleiotropy has traditionally complicated psychiatric classification because shared genetic influences make it difficult to draw clear biological boundaries between disorders.

She believes understanding these influences could help researchers develop treatments targeting shared genetic factors, potentially allowing a common therapy to help people with different psychiatric diagnoses.

That possibility remains a research goal rather than an established clinical option. Identifying a genetic variant that affects gene regulation is an important step, but scientists must still determine whether changing the relevant biological process would improve symptoms safely.

A treatment that works for one group of patients may not work for everyone with the same diagnosis. Psychiatric conditions are complex, and individual differences can influence how people respond to medication, psychotherapy, and other forms of care.

The findings therefore offer a direction for future research rather than evidence that a single treatment for all eight conditions is now within reach.

What The Findings Could Mean For Mental Health Care

The World Health Organization estimates that approximately one billion people worldwide live with a mental disorder. Understanding the biological factors involved in these conditions remains an important challenge for researchers seeking more effective treatments.

Genetic research could eventually help clinicians develop more precise approaches to diagnosis and care. Future methods may combine information about symptoms with a clearer understanding of the biological processes contributing to those symptoms.

The Nature researchers suggested that their findings could also inform future revisions to the Diagnostic and Statistical Manual of Mental Disorders, commonly known as the DSM. The handbook is widely used by mental health professionals to classify and diagnose psychiatric conditions.

However, Grotzinger emphasized that it is too early to combine diagnoses based on the genetic findings alone. Clinical symptoms and patient experiences remain essential when determining what care a person needs.

A shared genetic foundation does not mean two conditions are identical. Nor does it mean that someone diagnosed with one condition will necessarily develop another.

Instead, researchers hope that understanding common biological mechanisms will help explain why certain conditions overlap and identify new ways to address them. Such knowledge could eventually support more individualized treatment decisions.

Important Questions Remain Before Treatments Change

Several challenges remain before the findings can translate into new clinical treatments. Researchers must establish how particular genetic variants influence psychiatric symptoms in people and determine which biological pathways can be targeted safely.

Laboratory experiments can identify changes in gene regulation, but those changes do not automatically establish how a psychiatric condition develops in an individual. Further research is needed to connect these genetic effects with clinical outcomes.

Scientists must also consider the complexity of interconnected protein networks. Changing one part of a biological system could affect other processes, making it necessary to investigate both potential benefits and unintended consequences.

Environmental influences and life experiences also contribute to mental health. Genetic findings alone cannot explain every person’s symptoms or predict exactly how a condition will develop.

The next stages of research will need to connect genetic discoveries with clinical evidence and test whether targeting shared biological pathways can improve outcomes.

For people living with psychiatric conditions, the findings offer a clearer picture of why different diagnoses may overlap biologically. For researchers, they provide new leads to investigate as they work toward more precise treatments.

The key discovery is that psychiatric disorders may share more of their genetic foundations than their separate labels suggest. Understanding those connections could help scientists develop better ways to study mental illness, while ensuring that treatment continues to reflect the needs of each individual.