How the Immune System Could Be Key to Treating Mental Illness

Mental health conditions like depression, schizophrenia and bipolar disorder affect one in four people during their lifetime, yet the biological mechanisms behind them are still not fully understood. Now, researchers at the University of Bristol have found evidence that the immune system might play a causal role in these disorders, potentially opening the door to new treatments.

The study, led by Dr Christina Dardani and Professor Golam Khandaker at Bristol’s MRC Integrative Epidemiology Unit, used Mendelian randomisation – a technique that leverages genetic data – to explore whether immune proteins are involved in seven major mental health conditions: depression, anxiety, schizophrenia, bipolar disorder, Alzheimer’s disease, autism, and ADHD.

They analysed 735 immune-related proteins found in blood and discovered 29 that may play a causal role in these disorders. Of those, 20 are already the target of drugs approved for other conditions, which raises the possibility of repurposing existing treatments for mental health use.

Current treatments for disorders like depression and schizophrenia usually focus on brain chemicals such as serotonin and dopamine. But as one in three patients don’t respond to these treatments, researchers believe other factors must be at play.

Professor Golam Khandaker, Professor of Psychiatry and Immunology, said: “Our study demonstrates that inflammation in the brain and the body might influence the risk of mental health conditions.

“The findings challenge the centuries-old Cartesian dichotomy between the body and the mind, and suggests that we should consider depression and schizophrenia as conditions affecting the whole person.”

This work suggests a shift in how we understand and treat mental illness – from brain-only explanations to a more integrated view that includes the body’s immune system. The next step is to further investigate these findings through health record studies, animal models and early clinical trials to see whether targeting immune pathways can help improve mental health symptoms.