Conversion disorder is a poorly understood condition where physical symptoms, sometimes as severe as total paralysis, seem to be caused by psychological problems and have no basis in detectable damage to the nervous system or other parts of the body.
It is now thought that these sorts of problems occur on a continuum of medically unexplained symptoms and that milder forms are a significant part of a doctor’s caseload.
The second part of the programme discusses the dopamine hypothesis of psychosis, that argues that delusions and hallucinations can be largely explained by dysfunction to the dopamine systems in the brain.
My impression is that the discussion is a little uncritical of this over-simplified theory of the complex experience of psychosis, but is valuable as a clear explanation of the approach none-the-less.
Link to editorial from Canadian Journal of Psychiatry on conversion disorder and related conditions (see side panel for further articles).