How Do Mental Health Disorders Cluster in Families?

What you need to know

• In families with multiple members affected by mental illness, diverse psychiatric diagnoses tend to cluster together rather than just one specific disorder.

• Even individuals without a formal psychiatric diagnosis often have significant mental health symptoms.

• The findings support viewing mental health conditions through a “transdiagnostic” lens that looks at shared symptoms and mechanisms across disorders.

How mental health disorders cluster in families

Mental health conditions tend to run in families, but the patterns are complex. A new large-scale study from India sheds light on how psychiatric disorders cluster within families that have multiple affected members. The findings highlight the interconnected nature of mental health conditions and support looking at them through a “transdiagnostic” lens that focuses on shared symptoms and mechanisms across diagnostic categories.

Studying families with high rates of mental illness

The researchers studied 1,406 individuals from 481 families in India where multiple members were affected by mental health conditions. They focused on five major psychiatric disorders: substance use disorder, bipolar disorder, obsessive-compulsive disorder (OCD), schizophrenia, and Alzheimer’s disease.

This approach allowed them to examine patterns in families with an especially high genetic and environmental risk for mental illness. The families were identified through mental health services at the National Institute of Mental Health and Neurosciences in Bangalore.

Diverse diagnoses tend to cluster together

A key finding was that in 61% of the families studied, affected members had different psychiatric diagnoses rather than all having the same condition. For example, one family might include someone with bipolar disorder, another with OCD, and a third with substance use problems.

This suggests that what’s inherited may be a general vulnerability to mental health issues rather than a specific disorder. It fits with the idea that there are shared genetic and environmental risk factors that can manifest in various ways.

High rates of psychiatric symptoms, even without diagnoses

The researchers also found high rates of mental health symptoms across diagnostic categories and even in family members without a formal psychiatric diagnosis:

• 15% of those diagnosed with one of the five disorders studied actually met criteria for two or more of these conditions over their lifetime.

• 66% of all participants, including those without diagnoses, had clinically significant symptoms in at least one mental health domain in the previous two weeks.

• 40% of relatives classified as “unaffected” (without one of the five diagnoses studied) still had at least one significant psychiatric symptom.

Common symptoms across groups included depression, anxiety, sleep problems, and somatic (physical) complaints. This again points to overlapping mental health issues rather than distinct categories.

A transdiagnostic view of mental health

The study authors argue their findings support taking a “transdiagnostic” approach to understanding mental health. This means looking at shared symptoms, risk factors, and underlying mechanisms across diagnostic categories, rather than viewing disorders as separate entities.

Dr. Biju Viswanath, the study’s corresponding author, explains: “Our results show that psychiatric conditions don’t neatly segregate within families. There’s a complex interplay of genetic and environmental factors that can manifest in diverse ways. This suggests we may gain more insights by studying common elements across disorders rather than treating them as fully distinct.”

A transdiagnostic lens could potentially lead to more flexible, personalized approaches to diagnosis and treatment. It may also help identify individuals at risk earlier, before they meet full criteria for a specific disorder.

Implications for families

For families with a history of mental health conditions, these findings highlight the importance of being aware of diverse symptoms, not just those associated with diagnosed disorders in relatives. Seeking help early for any persistent mental health concerns is advisable.

The high rates of symptoms even in “unaffected” relatives also point to the value of mental health support for family members of those with psychiatric diagnoses. Caring for loved ones with mental illness can take a toll, and family members may have their own vulnerabilities.

Limitations and next steps

It’s important to note this study focused on families with unusually high rates of mental illness, so the findings may not generalize to all families or individuals. The research was also conducted in India, and patterns could differ in other populations.

Additionally, the study design can’t definitively say whether the clustering of diverse diagnoses is due to genetic factors, shared environments, or a combination.

The researchers are continuing to follow these families over time and conducting more in-depth biological studies. This may provide further insights into the shared and unique factors underlying different psychiatric conditions.

Conclusions

• Mental health conditions in families often cross diagnostic boundaries rather than clustering neatly into specific disorders.

• Even relatives without diagnoses often have significant psychiatric symptoms, suggesting a spectrum of vulnerability.

• A transdiagnostic approach looking at shared factors across disorders may offer valuable insights for understanding, preventing, and treating mental health conditions.