Scientists have identified hundreds of genetic variants that work like master switches, potentially revolutionizing how we treat conditions from autism to depression.
This discovery explains why these disorders often appear together and could lead to treatments that address multiple conditions simultaneously.
Picture this: a patient diagnosed with ADHD who also struggles with symptoms of depression. Or someone with autism who simultaneously battles anxiety.
For decades, psychiatrists have observed these overlapping conditions, treating each as separate entities requiring different medications and therapies.
But what if these seemingly distinct disorders actually stem from the same root cause?
A groundbreaking study published in the prestigious journal Cell has revealed that eight major psychiatric disorders—including autism, ADHD, schizophrenia, and depression—share common genetic foundations.
These shared genes don’t just contribute to multiple conditions; they operate like master regulators that influence brain development at numerous stages and across various cell types.
The discovery represents a fundamental shift in how we understand mental health conditions and could lead to revolutionary new treatments that address multiple disorders with a single approach.
The Genetic Connection Between Different Psychiatric Disorders
For years, scientists have observed that certain psychiatric conditions frequently occur together. For instance, up to 70 percent of people with autism also have ADHD, and these conditions often appear within the same families.
This clinical observation provided the first clue that these disorders might share underlying causes.
In 2019, an international research team identified 109 genes associated with eight different psychiatric disorders. This initial finding suggested a shared genetic basis, but the mechanisms remained unclear. How could the same genes contribute to conditions as seemingly different as anorexia and schizophrenia?
Dr. Hyejung Won, geneticist at the University of North Carolina and lead researcher of the new study, wanted to answer this question. Her team set out to understand exactly how these shared genes function and why they can lead to such different outcomes.
“We were particularly interested in what makes these shared genetic variants different from variants that only affect one specific disorder,” explains Won. “What we found was truly remarkable.”
How Shared Genes Function Differently
Won’s team examined almost 18,000 genetic variants—both those shared across multiple disorders and those unique to specific conditions. They introduced these variants into neural precursor cells—the cells that eventually develop into neurons—to observe how they influenced gene expression during human development.
This painstaking process allowed them to identify 683 specific genetic variants that actively impact gene regulation in developing brain cells.
The results revealed something surprising: genes shared across multiple disorders (called “pleiotropic” genes) have fundamentally different properties than genes linked to just one condition.
“The proteins produced by these genes are highly connected to other proteins,” explains Won. “Changes to these proteins in particular could ripple through the network, potentially causing widespread effects on the brain.”
In other words, these shared genes don’t just control one specific brain function—they influence entire networks of proteins and cellular processes. Like dropping a stone in a pond, alterations in these genes create ripples that affect numerous downstream processes.
Why Some Genes Affect Multiple Disorders
To further understand how these shared genes function, Won’s team also examined their activity in developing mouse brains. They discovered three key characteristics that differentiate the pleiotropic genes from disorder-specific genes:
- Broader cellular presence: The shared genes were active across many more types of brain cells than genes linked to just one disorder.
- Extended developmental activity: Pleiotropic genes remained active for longer periods during brain development, potentially influencing multiple developmental stages.
- Higher network connectivity: These genes participated in far more protein-to-protein interactions, allowing them to influence multiple brain systems simultaneously.
Dr. Jordan Smoller, professor of psychiatry at Harvard Medical School, who was not involved in the study, called the findings “a major advance in psychiatric genetics.”
“For decades, we’ve been stuck in a diagnostic system that treats these conditions as entirely separate entities,” Smoller says. “This research provides compelling evidence that many psychiatric disorders share fundamental biological mechanisms—and that has enormous implications for how we classify and treat these conditions.”
Challenging Traditional Views of Psychiatric Disorders
The traditional psychiatric approach has been to diagnose and treat mental health conditions as distinct disorders with clear boundaries. This research fundamentally challenges that paradigm.
Rather than viewing psychiatric conditions as separate entities, this genetic evidence suggests they exist on a spectrum with overlapping biological causes—similar to how different types of cancer can share common cellular mechanisms despite affecting different organs.
Dr. Won acknowledges this represents a significant shift in thinking. “Pleiotropy was traditionally viewed as a challenge because it complicates the classification of psychiatric disorders,” she says. “However, 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.”
This approach is particularly promising given the staggering prevalence of psychiatric conditions worldwide. The World Health Organization estimates that approximately one billion people—about 1 in 8 humans on the planet—live with some form of psychiatric condition.
Current treatments often address symptoms rather than underlying causes, and many patients don’t respond adequately to available therapies.
A treatment approach targeting shared biological mechanisms could potentially help millions of people who currently struggle with multiple psychiatric conditions.
From Genes to Therapies
While the research represents a significant breakthrough, translating these genetic findings into effective therapies remains a challenge. However, several promising approaches are already being explored:
- Network-based drug discovery: Rather than targeting single proteins, researchers are developing compounds that influence entire biological networks impacted by pleiotropic genes.
- Gene therapy approaches: Advanced techniques like CRISPR gene editing could potentially correct problematic regulatory regions identified in this study.
- Developmental timing interventions: Since these shared genes influence multiple stages of brain development, therapies that target specific developmental windows might prevent or mitigate multiple conditions simultaneously.
- Personalized medicine: Genetic testing could help identify which specific variants a patient carries, allowing for more tailored treatment approaches.
Dr. Benjamin Neale, a psychiatric geneticist at Massachusetts General Hospital and the Broad Institute, describes the potential impact: “This work gives us new targets that could influence multiple conditions at once. It’s like finding the shared roots feeding several different branches of a tree—address the roots, and you might improve the health of the entire system.”
Rethinking Diagnosis and Treatment
The findings also raise profound questions about how we diagnose and categorize psychiatric conditions. Our current diagnostic system—the Diagnostic and Statistical Manual of Mental Disorders (DSM)—classifies disorders based primarily on observable symptoms rather than underlying biology.
But if multiple conditions share common genetic causes, should we continue treating them as entirely separate disorders?
Dr. Thomas Insel, former director of the National Institute of Mental Health, has long advocated for a more biologically-based approach to psychiatric classification. “This study provides some of the strongest evidence yet that our current diagnostic categories don’t necessarily reflect the underlying biology,” Insel comments. “We may need to develop new frameworks that better reflect these shared genetic mechanisms.”
Some researchers envision future treatments targeting specific biological pathways rather than diagnostic categories. Under this approach, patients might receive therapies based on their genetic profile rather than their diagnostic label.
“Imagine being able to tell a patient, ‘You have variants in genes that regulate dopamine signaling, so this specific medication is likely to help—regardless of whether your symptoms fit neatly into ADHD, depression, or another category,'” explains Dr. Neale. “That’s the promise of this kind of research.”
Hope for Patients and Families
For people living with psychiatric conditions, these findings offer new hope. Many patients struggle with multiple diagnoses and take several medications with varying degrees of effectiveness. A more unified biological understanding could lead to simpler, more effective treatment approaches.
Sarah Johnston, whose 14-year-old son has both autism and ADHD, finds the research encouraging. “We’ve always felt there was something connecting his conditions. He takes different medications for different symptoms, but they interact and sometimes cancel each other out. The idea that there might someday be treatments that address the shared cause rather than just individual symptoms—that would be life-changing.”
The research also helps explain why psychiatric conditions often run in families, but in varied forms. One family member might have depression, another ADHD, and another anxiety—all potentially linked to the same underlying genetic variants expressed differently due to other genetic or environmental factors.
The Next Research Frontier
Won and her team are already planning follow-up studies to further understand how these pleiotropic genes function. Key questions include:
- How do environmental factors interact with these shared genetic variants?
- Why do the same genetic variants lead to different conditions in different people?
- At what stages of development might interventions be most effective?
- Can these findings help identify high-risk individuals before symptoms develop?
“We’re really just at the beginning of understanding the implications of this shared genetic architecture,” Won says. “But it opens up entirely new ways of thinking about these conditions and how we might treat them.”
The message for the millions of people affected by psychiatric disorders worldwide is clear: these conditions may be more biologically related than we ever realized—and that insight offers new paths toward more effective treatments.
As research continues to unravel the complex genetics of psychiatric disorders, the artificial boundaries between conditions may gradually dissolve, replaced by a more nuanced understanding of the brain’s development and function. For patients caught in the sometimes frustrating maze of psychiatric diagnosis and treatment, that future can’t come soon enough.
References
Won, H., et al. (2025). Pleiotropic genetic variants in psychiatric disorders orchestrate brain development via extensive protein networks. Cell.
Cross-Disorder Group of the Psychiatric Genomics Consortium. (2019). Genomic relationships, novel loci, and pleiotropic mechanisms across eight psychiatric disorders. Cell.
World Health Organization. (2024). Mental disorders fact sheet. WHO Global Health Database.
Smoller, J., et al. (2023). Psychiatric genetics and the structure of psychopathology. Nature Reviews Neuroscience.
Insel, T. (2022). Healing: Our Path from Mental Illness to Mental Health. Penguin Random House.
National Institute of Mental Health. (2024). Research Domain Criteria (RDoC) Framework. NIMH Publications.
