Our knowledge about marihuana is incomplete, but certain behavior characteristics appear to be emerging in regard to long term American marihuana use which, for the most part, is significantly less than 10 years. These impressions were confirmed in the Boston free-access study. The group of American young adults studied averaged five years (range 2-17 years) of intermittent or daily use, of marihuana.

No significant physical, biochemical, or mental abnormalities could be attributed solely to their marihuana smoking. Some abnormality of pulmonary function was demonstrated in many of the subjects which could not be correlated-with quantity, frequency or duration of smoking marihuana and/or tobacco cigarettes. (One other investigation recently completed uncovered no abnormalities in lung or heart functioning of a group of non-cigarette smoking heavy marihuana users). Many of the subjects were in fair to poor physical condition, as judged by exercise tolerance.

The performance of one-fifth of the subjects on a battery of tests sensitive to brain function was poorer on at least one, index than would have been predicted on the basis of their IQ scores and education. But a definite relationship between the poor test scores and prior marihuana or hallucinogen use could not be proven.

In the past few years, observers have noted various social, psychological and behavioral changes among young high school and college age Americans including many who have used marihuana heavily for a number of years. These changes are reflected by a loss of volitional goal direction. These individuals drop out and relinquish traditional adult roles and values. They become present rather than future oriented, appear alienated from broadly accepted social and occupational activity, and experience reduced concern for personal hygiene and nutrition.

Several psychiatrists believe they have detected clinically that some heavy marihuana-using individuals appear to undergo subtle changes in personality and modes of thinking, with a resulting change in life style. In adopting this new life style, a troubled youth may turn toward a subculture where drug use and untraditional behavior are acceptable.

This youthful population resembles in many respects the marihuana smoker described in the Boston study. No evidence exists to date to demonstrate that marihuana use alone caused these behavioral changes either directly or indirectly. Many individuals reach the same point without prior marihuana use or only intermittent or moderate use; and many more individuals use marihuana as heavily but do not evidence these changes. For some of these young people, the drop out state is only a temporary phase, preceding a personal reorganization and return to a more conventional life style.

If heavy, long-term marihuana use is linked to the formation of this complex of social, psychological and behavioral changes in young people, then it is only one of many contributing factors.