Not feeling very social these days? Your immune system could be the culprit, according to a new study that might change the way doctors diagnose and treat conditions such as schizophrenia and autism spectrum disorders.

For the study, researchers at the University of Massachusetts Medical School and the University of Virginia (UVA) tracked an immune system molecule called interferon gamma in lab mice to see how it affected their social responses to one another. Interferon gamma is released by lymph cells in response to pathogens. But researchers found that when they blocked these molecules, the mice became "hyperactive" and uninterested in social interaction with the other mice. When the researchers stopped blocking the interferon gamma, the mice returned to their normal behavior and were once again interested in socializing.

Researchers came up with an evolutionary theory to explain the relationship, noting that the evolution of humans has depended upon our social interactions with one another, so it makes sense that the body would amp up the immune response when we are socializing to protect the individual and the herd.

Studies have long shown a person's mental health can have a direct effect on physical health. Depression and social isolation are more closely linked to chronic illness while happiness is aligned with better overall health. But this new research suggests the link might work in reverse as well — that the strength of the immune system might play a role in a person's mental state. The research team hopes this study can serve as a starting point for continued research on the immune system and its effect on social interactions and disorders.

“It’s crazy, but maybe we are just multicellular battlefields for two ancient forces: pathogens and the immune system. Part of our personality may actually be dictated by the immune system,” said Jonathan Kipnis, chair of UVA’s Department of Neuroscience and one of the authors of the study. You can hear more from Kipnis in this video: