[droithomme]

This is covered quite thoroughly in chapter 6 of Whitaker's Anatomy of an Epidemic, which has extensive citations of the history and research on this problem.

Neuroleptics make schizophrenia patients more biologically vulnerable to psychosis. Standard antipsychotics block 70-90% of D2 receptors in the brain. To compensate, postsynaptic neurons increase the density of their D2 receptors by 30% or more. The brain is then supersensitive to dopamine. This leads to dyskinetic and psychotic symptoms.