Since the Second World War, rates of common mental illness (depression and anxiety) have been increasing in the industrialized nations, whereas rates of recovery from severe mental illness have not improved despite the availability of apparently effective therapies such as antipsychotic drugs.

The only way you can estimate environmental influences is by measuring them.

My interest in the psychological roots of psychosis has both personal (my brother Andrew committed suicide) and professional origins (I was trained in a behaviorist approach to psychology which - whatever its limitations - at least taught me to see human behavior in its social context).

At the individual level, if we can identify the psychological mechanisms linking adverse environments to psychosis (and there has been a lot of progress with this despite minimal funding) we should be able to devise more effective interventions for those who are already ill.

If we are to believe the evidence from clinical trials there are many effective pharmacological and psychological treatments for mental illness. Epidemiological data, on the other hand, says otherwise.

There are many kinds of adult adversities that can provoke severe psychological distress, including debt and unemployment, dysfunctional marital relationships and occupational stress. The reality is that the social causes of mental ill-health are all around us.

Conventional psychiatry has emphasized the genetic roots of psychosis based on the claim that twin and other studies show that schizophrenia is 80% heritable, which means that 80% of the cause is genetic.