Drug Watch International

MARIJUANA RESEARCH REVIEW                                                     

Prenatal exposure to cocaine and marijuana may lead to craving by infant

Mirochnick et al. checked forty-six infants for levels of the hormones norepinephrine and adrenaline at birth. Twenty-four were cocaine exposed during pregnancy and twenty-two were not. The cocaine-exposed babies had a 22% increase in levels of norepinephrine, which increased to 75% if marijuana was also used by the pregnant mother. There were neurobehavioral abnormalities in the babies at one to three days of age which disappeared by two weeks (Pediatrics 99:555-559,1997). 

Comment: The chronic use of cocaine, particularly when used with marijuana, sets up craving behavior by depleting brain dopamine and norepinephrine. Exposure during pregnancy increases the levels of these hormones, which may lead to drug craving in the infant during withdrawal after birth. Recent studies in rats (French et al, Neuro Report 8:649-652,1997) have shown that psychoactive cannabinoids increase dopamine levels in brain tissue contributing to the addictive effects of marijuana. ##

Impact of marijuana intoxication on the brain

Blood flow to the brain was studied in 32 volunteers who had a mean age of 32.5 years and a history of exposure to marijuana (Mathew, et al, Life Sciences, 60:2075-20-87,1997). This was a double blind study performed before and after intravenous injection of THC at the rate of either 0.25 mg/mm or 0.15 mg/mm, compared to placebo. The results showed that THC, but not the placebo, increased brain blood flow, particularly in the frontal part of the brain and correlated with the volunteers' analysis of whether or not they were high. Changes in the higher dose group could be detected sooner (within 30 minutes) than those in the lower dose group. This study shows that THC impacts activity in the part of the brain that is associated with memory and stress-induced cardiovascular responses, and particularly in the part of the brain involved in emotion and short-term memory. This study may provide a physiologic basis for the brain side effects seen with marijuana use.

Comment: The study provides dramatic evidence that acute use of marijuana, when it gains access in the blood stream, can significantly alter blood flow to the brain, particularly in areas that concern memory, emotion, and behavior. The structured clinical interview form used in this study includes criteria for abuse or dependence for alcohol or any other substance. However, prior to the experiments none of the volunteers had had evidence of either. This data shows that alterations in perception, emotion, and motor skills may be present in users of marijuana even when it has a very low THC content. ##

New controlled study compares alcohol and marijuana impairment

A double-blind placebo-controlled study was done by Heishman et al (Pharmacology Biochemistry and Behavior, Vol.5, No.1, pp 93-101,1997) using normal male volunteers with histories of moderate regular alcohol and marijuana use. Marijuana cigarettes used in the study were obtained from the National Institute on Drug Abuse (NIDA) Marijuana Research Center and contained 3.55% THC. Alcohol used in the study was 95% ethanol. Blood levels of alcohol and THC confirmed that active drug was delivered to the patients.

The outcome measures in this study were a subjective perceived rating of impairment on the part of the patient, and their objective performance in word recall and other measures. Results showed that there was a dose-­dependent relationship between the subject's perception of what the drug did and the performance on the objective tests. High doses of alcohol and marijuana caused all of the subjects to perceive that they were impaired. Both drugs produced "remarkably" comparable impairment on objective tests of word recall and digit substitution, and psychomotor and cognitive abilities. Alcohol, but not marijuana, impaired performance in number recognition, and marijuana, but not alcohol, caused a rapid heart rate (tachycardia).

Comment: This well-performed study by Heishman and colleagues elegantly substantiates observations made in many previous studies that even small doses of alcohol and marijuana impair performance. Studies such as this have implications for motor vehicle safety, occupational health, academic achievement, and job performance. While this study did not address poly-drug use, in real life alcohol is frequently used with other drugs and one could anticipate an additive, or perhaps even a synergistic effect.

The observation of marijuana induced tachycardia (rapid heart beat) should not be overlooked, particularly for those suffering ill health or with underlying heart disease. The data developed in this research further accentuates why any effort to increase public access to marijuana should be strongly resisted. ##

Significant predictors of marijuana dependency extracted from national surveys

Researchers used data from three National Household Surveys on Drug Abuse taken between 1991 and 1993 to analyze and measure the degree of marijuana dependence in over 9,000 adults and adolescents who had used marijuana during the past year. Standard criteria of dependence were used to evaluate symptoms of dependence and drug related problems reported by individuals using the drug. The study found that frequency and quantity of marijuana use were primary predictors for dependency on this drug. Other significant predictors of marijuana dependence were adolescence, graduation from high school or college, adequate median family income, and living on the West Coast. At any level and frequency of marijuana use, adolescents became dependent more often than adults, and this was particularly seen as "low level" exposure increased to more regular use, i.e., nearly 35% of adolescents who used marijuana daily were identified as being dependent as opposed to only 18% of daily users in the adult subjects. No significant differences in dependency were noted between men and women.

Comment: This study provides additional support for the now well-accepted phenomenon among addiction specialists that marijuana frequently produces a dependency syndrome like other mind-altering drugs, and that youth are far more susceptible to dependency than adults. It is likely that the reported rate of dependency was underestimated by the researchers (Chen et al, Drug and Alcohol Dependence Vol.46, 1997, pp 53-67) since the symptoms of dependence and drug-related problems on which they based their study were largely self-reported. However, the large number of subjects in this study makes it highly relevant, and the observations of the study should be seen as a cause for alarm considering the spiraling escalation of marijuana use by adolescents coupled with the widespread misconception that the drug is harmless. ##

Dust in cannabis hemp factories has deleterious impact on workers

Cannabis hemp has not been commercially grown or processed in the United States since the 1930's except for a brief period during World War II when the supply of Manila hemp, used for military purposes, was interrupted. Today, only a few underdeveloped countries grow cannabis hemp, including the former Yugoslavia. A study by Zuskin et al, re-examined 66 Yugoslavian men and women who had participated in a lung function study three years earlier. Though no longer exposed to particulate matter from hemp manufacturing, nearly 50% of the 38 women in the study and 65% of the 28 men (many of whom were tobacco smokers), had evidence of chronic lung damage (byssinosis). There was a decrease in the ability to exhale air even in non-users of tobacco, suggesting that hemp dust by itself could produce these changes. Dust levels in the Yugoslavian hemp factories were "much higher than those found in mills processing organic materials in North America." (Am J Ind Med, 26, 103-115,1994).

Comments: The authors stated that their data "demonstrated that work in the hemp industry... continues to have deleterious effects on respiratory function." Current efforts to reintroduce commercially grown cannabis for hemp production in the United States should consider potential health hazards. Hemp manufacturing may be an unnecessary risk considering the negative health aspects and the fact that numerous other superior fiber bearing plants, already being grown commercially in the United States, produce less dust. These other plants have no psychoactive properties and cause less damage to the environment. Additionally, production of cannabis hemp in the U.S. would require strict and costly safety precautions, likely to make the U.S. grown product commercially unviable. ##

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Material used in this publication has been reviewed and commented on by William M. Bennett, M.D., Professor of Medicine, Division of Nephrology, Clinical Pharmacology and Hypertension at Oregon Health Sciences University, Portland, Oregon

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