Depression or psychotic illness is experienced by hundreds of thousands, perhaps millions, of people in the UK. James Gallagher talks to the psychiatrists investigating this new understanding of mental illness and to people who may benefit from treatments aimed at the immune systems rather than their brain cells.

“I believe this is one of the strongest discoveries in psychiatry in the last twenty years”, says Professor Carmine Pariante of his and other research on the immune system and depression. "It allows us to understand depression no longer as just a disorder of the mind and not even a disorder of the brain, but a disorder of the whole body. It shifts conceptually what we understand about depression."

James also talks to New York journalist Susannah Cahalan. She began to experience paranoid delusions and florid hallucinations when her immune system made damaging antibodies against part of the molecular circuitry in her brain. Treatment to eliminate the antibodies prevented her committal to psychiatric hospital. Psychiatrist professor Belinda Lennox at the University of Oxford says she has evidence that a significant proportion of people presenting for the first time with psychotic symptoms are victims of a similar autoimmune problem.

(Photo: Brain Cells © Science Photo Library)