Toxic cannabis psychosis is a valid entity.

One hundred black men admitted to hospital with acute psychiatric symptoms were investigated for the presence of urinary cannabis metabolites in order to delineate the psychiatric role played by 'dagga', the potent South African cannabinol, in the study population and to determine the diagnostic value of the entity 'toxic psychosis (dagga)'. Cannabinoids were present in 29% of patients, and 31% were discharged with a diagnosis of toxic psychosis (dagga). Clinical and demographic material was gathered for all patients and no consistent differences were found between dagga-positive and dagga-negative patients or toxic dagga psychotic patients and 'functional' psychotics other than a history of recent dagga use and the dagga screening test result. The latter measure was found to be both more sensitive and more specific than the history of dagga use alone. The findings support the routine use of a simple screening test for dagga in the sample population studied. The study demonstrated the heterogeneous nature of the toxic dagga psychosis syndrome by documenting a variety of different clinical presentations, which included schizophrenia (42%), paranoia (26%), maniform psychosis (16%) and organic psychosis (16%).