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Marihuana, A Signal of Misunderstanding - Table of Contents

The Report of the National Commission on Marihuana and Drug Abuse

Effects of Long-Term Cannabis Use


Deterioration of mental functioning allegedly due to long-term use of marihuana can be subdivided into four major categories: organic brain damage, mental illness-psychosis, amotivational syndrome, and recurrent-pnuenomenia. As with alcoholism, it is quite often impossible to distinguish whether the described effects result from drug use or represent personality traits or changes which would have been present without the drug use.

When marihuana consumption was irregular, mental deterioration was not evidenced (Freedman and Rockmore, 1946) in 310 users with an average history of seven years of use. Sixty-seven heavy users in New York showed no evidence of dementia attributable to drug use although they did have underlying personality disorders. Another investigation (Mayor's Committee, 1944) of individuals who used a daily average of seven marihuana cigarettes (two to 18 range) for average of eight years (two-and-a-half to 16 range) showed no evidence of brain damage or mental deterioration.

Reports from India (Chopra, 1935; Chopra, 1940; Chopra and Chopra, 1939; Chopra, Chopra, and Chopra, 1942) relate minor impairment of judgment and memory, limited self -neglect and insomnia, when potent preparations are consumed regularly in large amounts for many years. No evidence for mental deterioration or brain damage has been noted.

Miras (1967) has described a Greek population of heavy hashish smokers who appear as outcasts from the community after 15 to 20 years of heavy hashish use. They appear mentally sluggish and depressed. They are reported to exhibit laziness, psychic instability, amorality and apparent lack of drive and ambition. Their speech and behavior has been described as -peculiar. Some degree of responsibility is retained in that some do work to cover their living and drug purchasing expenses. Some of them are still quite intelligent. Memory is not deteriorated except during the intoxication. They appear overly suspicious. Samples of their electroencephalograms were believed to demonstrate abnormalities.

However, Miras believes that this effect is related to the quantity and frequency of hashish use. He describes three categories of long-term hashish users. Type A uses low doses intermittently and is socially and mentally unaffected. Type B1 uses low doses daily and no interference is caused in function. Type B 2 uses high doses daily causing dependence and performance decrements. Type C uses very high doses daily allegedly causing mental deterioration and abnormal behavior described above. Fink and Dornbush (1971) are currently intensively studying this population. The results will be described in a later section.

Non-differentiated psychosis noted in foreign populations may also be included within this diagnostic category. These will be discussed with the psychosis.

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