To determine the long-term chronic effects of heavy marihuana use, the Commission has carefully reviewed the world literature and contemporary studies of heavy, chronic (up to 41 years) cannabis users in the world. In addition, lower socioeconomic populations in Afghanistan, Greece, and Jamaica have been examined.

Effects On The Body

These recent studies in Greece and Jamaica report minimal physical abnormalities in the cannabis users as compared with their non-using peers.

Minimal abnormalities in pulmonary function have been observed in some cases of heavy and very heavy smokers of potent marihuana preparations (ganja or hashish). However, one study concluded the cause was smoking in general no matter what the substance. The other study could not express any conclusion because of the absence of a control population. Such decrements in normal pulmonary capacity may represent early warning signals in the development of chronic lung disease. They must be considered in any program of early prevention of disease and future disability.

No objective evidence of specific pathology of brain tissue has been documented. This fact contrasts sharply with the well-established brain damage of chronic alcoholism.

Effects On The Mind

No outstanding abnormalities in psychological tests, psychiatric interviews or coping patterns have been conclusively documented in studies of cannabis users in other countries of the world. Further research in this important area is necessary before definite conclusions can be drawn relating or linking marihuana to mental dysfunction because available psychological tests do not measure certain higher mental functions very accurately.

Cannabis use has long been known to precipitate short-term phychotic-like episodes in predisposed individuals or those who take excessive doses. Some observers report that the prevalence of shortterm psychoses as well as the psychotic episodes of longer duration in heavy cannabis users are compatible with the prevalence rate of psychosis in the general population and, therefore, may not be attributable to cannabis use. In fact, some believe that in populations under stress where marihuana is widely used, occurrence of the acute psychotic-like episodes occur less often than one would expect in such a population. Other researchers have disagreed with these conclusions, and the matter is still controversial.

Effects On Motivation

The Commission is deeply concerned about another group of behavioral effects that have been described in other nations as being associated with the heavy, long-term use of cannabis. This behavioral condition has been termed the "amotivational syndrome." An extreme form has been reported in populations of lower socioeconomic males in several developing nations. These reports describe lethargy, instability, social deterioration, a loss of interest in virtually all activities other than drug use. This state of social and economic disability also results in precipitation and aggravation of psychiatric disorders (overt psychotic behavior) and possible somatic complications among very heavy, very long-term users of high potency cannabis products. However, in the populations so far observed in Jamaica, Greece, and Afghanistan, physical and psychosocial deterioration was not reported. The life styles of these populations appeared to be conditioned by cultural and socioeconomic factors. Some researchers believe cannabis' may serve to keep these individuals stratified at this lower socioeconomic level.

The occurrence of a similar, though less intense, syndrome has been identified recently with heavy marihuana use among young persons in the Western world, including the United States. Some clinicians have described the existence of a complex of subtle social, psychological and behavioral changes related to a loss of volitional goal direction in certain individuals, including some long-term heavy users of marihuana. Such persons appear to orient only to the present. They appear, alienated from generally accepted social and occupational activities, and they tend to show a reduced concern for personal hygiene and nutrition.

Some clinicians believe that this picture is directly caused by the action of marihuana. However , other behavioral scientists believe that among impressionable adolescents, marihuana-induced suggestibility may facilitate the rapid adoption of new values and behavior patterns, particularly when the drug is taken in a socially alienated subculture that advocates and strongly reinforces such changes.

Whichever interpretation one accepts, the fact is apparent that the chronic, heavy use of marihuana may jeopardize social and economic adjustments of the adolescents We believe this is one concern which merits further research and evaluation. On the basis of past studies, the chronic, heavy use of marihuana, seems to constitute a high-risk behavior, particularly among predisposed adolescents. This consideration is especially critical when we consider the adolescent who is in the throes of a normally turbulent emotional process. The Commission has reviewed numerous reported studies and heard the testimony of several clinicians dealing with heavy users of marihuana who exhibit this particular behavior pattern. Although the United States does not, at the present time, have a large number of such persons within its population, the incidence is too frequent to ignore. Expanded epidemiologic studies are imperative to obtain a better understanding of this complex behavior.