VIRAL-MI publishes first study on infections and mental health

Can infections throughout life shape our vulnerability to mental illness? A new study from the international VIRAL-MI research collaboration provides important clues.

Published in Translational Psychiatry, the study investigated whether infections acquired in everyday life are associated with the later development of mental disorders. While previous research has often focused on severe infections requiring hospitalisation, VIRAL-MI researchers wanted to look at something much more common: infections that people experience in the community.

The researchers analysed health records from 35,020 people with a history of specific infections and compared them with 35,020 matched individuals without such infections. Participants were followed until 2024, with researchers looking at the subsequent onset of anxiety, depression, schizophrenia and bipolar disorder. The infections studied included cytomegalovirus, herpesviruses, hepatitis, influenza and Toxoplasma gondii.

More infections, greater vulnerability?

One of the most striking findings was that the association became stronger as the number of infections increased. Compared with people without a history of these infections, the risk of developing a mental disorder was:

• 8% higher after one infection

• 19% higher after two infections

• 81% higher after three or more infections

These associations were particularly pronounced in women, older individuals and people from larger families.

Importantly, these findings do not mean that an infection directly causes a mental disorder. Mental health is shaped by many interacting biological, psychological and environmental factors. Instead, the results suggest that repeated immune challenges may be one of the factors that influence an individual's vulnerability to mental illness.

A new perspective on mental health

The findings support a growing research perspective in which the immune system, infections and mental health are studied as interconnected parts of the same biological system.

For VIRAL-MI, this is an important first step towards a bigger question: how do the viruses and other infections we encounter throughout our lives interact with our biology and shape our vulnerability to mental illness?

By bringing together researchers from psychiatry, immunology, infectious diseases and epidemiology, VIRAL-MI aims to move beyond studying individual infections in isolation and towards understanding the cumulative impact of our infectious history on mental health.

Read the full paper: Community-based infections and its association with mental disorder onset: a nationwide matched cohort study, published in Translational Psychiatry on 17 August 2026.

Read the full paper in Translational Psychiatry