The presence of two antibodies may trigger episodes of psychosis in children, says a study, affirming a longstanding belief that auto-immune disorders play a significant role in psychiatric illnesses.

Antibodies defend the body against bacterial, viral, and other invaders but sometimes the body makes antibodies that attack healthy cells. In these cases, auto-immune disorders develop. 

These include conditions such as multiple sclerosis, rheumatoid arthritis and Type 1 diabetes.

In the new study, published in the journal Biological Psychiatry, the researchers detected two antibodies among eight out of 43 children experiencing their first episode of psychosis, but no such antibodies in healthy children.

The antibodies to the dopamine D2 receptor or the N-methyl-D-aspartate (NMDA) glutamate receptor are key neural signalling proteins previously been implicated in psychosis.

"The antibodies we have detected in children having a first episode of acute psychosis suggest there is a distinct subgroup for whom auto-immunity plays a role in their illness," said senior study author Fabienne Brilot from the University of Sydney.

"The finding suggests that better interventions are possible, providing hope that major disability can be prevented for the subset of children experiencing acute psychosis with antibodies," Brilot added.