From schizophrenia to depression we assume our psychiatric diagnoses are real. But as the mental health epidemic turns global, the categories now seem like the cause. Is it time to abandon our biological account of mental illness? Or is it the best strategy we've got?

Polly Toynbee interrogates Cambridge psychologist Simon Baron-Cohen, author of Madness Explained Richard Bentall and Professor of Mental Health at King's College Dinesh Bhugra.

From the Institute of Art and Ideas collection.