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.
Childhood trauma is not necessarily a prophecy of doom, because some children are resilient or because later experiences help to restore mental health.
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.
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.
Countries with the best-resourced medical services have the best outcomes for physical illness (it is better to have a heart attack in Washington or London than in rural Africa) whereas precisely the opposite is the case for mental illness (developing nations with limited psychiatric resources have better outcomes and lower suicide rates).
There is almost no evidence that diagnoses such as 'schizophrenia' and 'bipolar disorder' correspond to discrete entities ('natural kinds' in the language of philosophy).
At the population level, making the world more just and less unequal, while trying to figure out the toxic aspects of the urban environmental will probably help prevent a lot of psychosis.
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.
There is also evidence from epidemiological studies that psychotic-like experiences are much more common than has hitherto been thought (with about 10% of the population affected) and that these experiences exist on continua with healthy or 'normal' functioning: instead of the world falling into two groups (the psychotic and the non-psychotic) people vary in their disposition to psychosis and only a minority of people who have these experiences require or seek help.
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).
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.
The only way you can estimate environmental influences is by measuring them.
