The literature on the relationship of cannabis to the development of psychosis is both vast and exceedingly confused, and as one reads through its more noteworthy contributions, a definite dichotomy, one based largely on locale and observer, becomes evident. Authors from India, Egypt, Turkey, Africa, and other Eastern lands are largely in agreement that their psychiatric institutions are populated by a large number of cases of insanity which can be directly attributed to hashish. In the late 1800's and early 1900's particularly, but even as late as 1967, papers and official statements appeared which adamantly condemn the drug as harmful both to the mental health of the individual and to the integrity of the social fabric of their countries. It is striking that numerous discussions of the psychotogenic effects of cannabis in Western literature (notably those written recently in the United States) are in quite an opposite vein; they either exonerate marihuana from these charges or else cite only a handful of cases to support the contention that its use leads to the development of psychoses. Clearly, there are some discoverable factors or circumstances which account for the existence of such a wide dichotomy in world medical opinion. A critical look at this literature may reveal some reasonable conclusions that can be drawn with regard to cannabis and psychosis.
Examining first the Eastern literature, one is immediately impressed with the magnitude of the role that cannabis apparently plays in admissions to psychiatric facilities. Authors from the East would have us believe that anywhere from one-fourth to ninetenths of the admissions to their institutions result from the use