We are still not entirely sure how psychoactive drugs work on the brain. As Angell notes, the very first drugs used to treat psychosis were in fact discovered completely by accident. Early anti-psychotics were originally designed to treat infections but were soon discovered to also alter patients' mental states. Further research revealed that these drugs worked on neurotransmitters in the brain, a discovery that represented an important leap in the field of psychiatry. Unfortunately, the "chemical imbalance theory" of mental illness, so widely accepted, is not always supported by current scientific evidence.

In reviewing this evidence, Angell cites the work of Irving Kirsch, PhD, a professor of psychology at the University of Hull. Kirsch