Schaffer Library of Drug Policy

Marihuana: A Signal of Misunderstanding

Investigations of Very Heavy, Very Long-Term Cannabis Users - Summary

US National Commission on Marihuana and Drug Abuse

Table of Contents
I. Marihuana and the Problem of Marihuana
Origins of the Marihuana Problem
The Need for Perspective
Formulating Marihuana Policy
The Report
II. Marihuana Use and Its Effects
The Marihuana User
Profiles of Users
Becoming a Marihuana User
Becoming a Multidrug User
Effects of Marihuana on the User
Effects Related to Pattern Use
Immediate Drug Effects
ShortTerm Effects
Long Term Effects
Very Long Term Effects
III. Social Impact of Marihuana Use
IV. Social Response to Marihuana Use
V. Marihuana and Social Policy
Drugs in a Free Society
A Social Control Policy for Marihuana
Implementing the Discouragement Policy
A Final Comment
Ancillary Recommendations
Legal and Law Enforcement Recommendations
Medical Recommendations
Other Recommendations
Letter of Transmittal
Members and Staff
History of Marihuana Use: Medical and Intoxicant
II. Biological Effects of Marihuana
Botanical and Chemical Considerations
Factors Influencing Psychopharmacological Effect
Acute Effects of Marihuana (Delta 9 THC)
Effects of Short-Term or Subacute Use
Effects of Long-Term Cannabis Use
Investigations of Very Heavy Very Long-Term Cannabis Users
III. Marihuana and Public Safety
Marihuana and Crime
Marihuana and Driving
Marihuana - Public Health and Welfare
Assessment of Perceived Risks
Preventive Public Health Concerns
Marihuana and the Dominant Social Order
The World of Youth
Why Society Feels Threatened
The Changing Social Scene
Problems in Assessing the Effects of Marihuana
Marihuana and Violence
Marihuana and (Non-Violent) Crime
Summary and Conclusions: Marihuana and Crime
Marihuana and Driving
History of Marihuana Legislation
History of Alcohol Prohibition
History of Tobacco Regulation
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National Commission on Marihuana and Drug Abuse

Investigations of Very Heavy, Very Long-Term Cannabis Users


Marihuana has been used by man in countries around the world for many centuries. Scientifically, more is known about marihuana's effects than many other botanical substances consumed by man.

Marihuana is one of several preparations from the plant, cannabis sativa. The plant contains many different chemicals, but tetrahydrocannabinol appears to be the major active psychopharmacologic ingredient. The potency of the preparation is determined by the THC content, which varies according to the origin of the seed, the conditions of cultivation, and the extent of manicuring.

Several important factors exert significant influences on the psychopharmacological effect. These include dose, method of use, set and setting, and pattern of use including frequency and duration of use.

The acute subjective experience is dose-dependent. At low doses commonly used in this country a mild intoxication occurs, but at higher doses psychotomimetic experiences can occur. Few consistent physiological effects are noted. No pathologic bodily changes have been conclusively demon, strafed from acute use. Subtle effects on recent memory, psychomotor function, and social behavior have been demonstrated.

The margins of safety between the effective dose and the toxic dose is quite large. No human fatalities have been noted in this country caused by marihuana. The most common adverse reactions are becoming too intoxicated, and the acute anxiety panic reaction. Both of these are transient and related to dose consumed as well as set and setting factors.

Acute psychotic, reactions are quite rare. They usually last a few days to weeks and occur in predisposed persons either with preexisting mental disorders or borderline personalities especially under stressful conditions. Transient acute brain syndrome or toxic psychosis is possible at extremely large doses.

Evidence has accumulated which indicates that differential tolerance does develop at least, in persons who smoke large amounts of marihuana several times a day. Development of tolerance to the depressant effects on behavior appears to precede development of tolerance to the intoxicant effect.

Physical dependence has not been demonstrated. Little, if any, psychological dependence is present in most intermittent marihuana users. Moderate psychological dependence occurs in moderate to heavy users and marked psychological dependence has been described in very heavy chronic users.

Some detrimental effects have been conclusively linked to short- and long-term marihuana use for very heavy users. The most frequently reported change in the heavy, long-term smokers of large quantities of potent preparations is chronic bronchitis comparable to that developed by a heavy, long-term tobacco cigarette smoker. A chronic cannabis psychosis probably occurs rarely in heavy chronic, hashish smokers in Eastern countries. Most psychotic episodes are the acute variety and clear in a few days to weeks. No objective evidence has been demonstrated that even very heavy, long-term hashish use causes organic brain damage.

Objective studies of chronic, heavy smokers of potent preparations have not causally linked this drug with the amotivational syndrome which has been described by many clinicians. Almost all chronic, heavy hashish smokers are indistinguishable from their peers in the lower socioeconomic strata of their respective societies in social behavior, work performance, mental status and overall life style.

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