Delusional disorders are a naturally occurring 'experimental psychosis'.

A delusion can only be 'explained' if it can be correlated with a demonstrable brain event, and this is only beginning to be possible. The misidentification syndromes are leading the way in demonstrating a close relationship between quite specific brain abnormalities and highly characteristic delusional symptoms. Although delusional disorder (DSM-IV 297.10) and its treatment are well described, virtually no investigations have been carried out on the neuropathological substrate. This article suggests that delusional disorder is a naturally occurring 'model psychosis' which would reward experimental study.