Cannabis and psychosis: revisiting a nineteenth century study of 'Indian Hemp and Insanity' in Colonial British India.

This important nineteenth-century study observed frequency and dose-related effects of cannabis on mental health, particularly psychotic symptoms in young people with a previous or hereditary risk of mental illness. Pathophysiological observations were consistent with current knowledge. As one of the most systematic and detailed studies of the effects of cannabis of the time it foreshadowed contemporary cannabis issues.