Marijuana Use During Pregnancy Harms The Fetus!

Exposing Marijuana Myths: A Review of the Scientific Evidence




Marijuana Use During Pregnancy Harms The Fetus



A powerful accusation in anti-drug campaigns is that children are permanently harmed by their mothers' use of drugs during pregnancy. Today, it is commonly claimed that marijuana is a cause of birth defects and development deficits.


The Facts


A number of studies claimed reported low birth weight and physical abnormalities among babies exposed to marijuana in utero. 43 However, when other factors known to affect pregnancy outcomes were controlled for—for example, maternal age, socioeconomic class, and alcohol and tobacco use—the association between marijuana use and adverse fetal effects disappeared. 44
Numerous other studies have failed to find negative impacts from marijuana exposure. 45 However, when negative outcomes are found, they tend to be widely publicized, regardless of the quality of the study.


It is now often claimed that marijuana use during pregnancy causes childhood leukemia. The basis for this claim is one study, in which .5% of the mothers of leukemic children admitted to using marijuana prior to or during pregnancy. A "control group" of mothers with normal children was then created and questioned by telephone about previous drug use. Their reported .5% marijuana use-rate was used to calculate a 10-fold greater risk of leukemia for children born to marijuana users. 46 Given national surveys showing marijuana prevalence rates of at least 10%, these "control group" mothers almost certainly under-reported their drug use to strangers on the telephone.


Also used as evidence of marijuana-induced fetal harm are two longitudinal studies, in which the children of marijuana users were examined repeatedly. However, on closer examination, the effects of marijuana appear to be quite minimal, if existent at all.


After finding a slight deficit in visual responsiveness among marijuana-exposed newborns, no differences were found at six months, 12 months, 18 months, or 24 months. 47 At age 3, the only difference (after controlling for confounding variables) was that children of "moderate" smokers had superior psycho-motor skills. At age 4, children of "heavy" marijuana users (averaging 18.7 joints/week) had lower scores on one subscale of one standardized test of verbal development. 48 At age 6, these same children scored lower on one computerized task—that measuring "vigilance." On dozens of others scales and subscales, no differences were ever found. 49


In another study, standardized IQ tests were administered to marijuana-exposed and unexposed three year-olds. Researchers found no differences in the overall scores. However, by dividing the sample by race, they found—among African-American children only—lower scores on one subscale for those exposed during the first trimester and lower scores on a different subscale for those exposed during the second trimester. 50


Although it is sensible to advise pregnant women to abstain from using most drugs—including marijuana—the weight of scientific evidence indicates that marijuana has few adverse consequences for the developing human fetus.

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Marijuana Causes Lung Disease!

Exposing Marijuana Myths: A Review of the Scientific Evidence


Marijuana Causes Lung Disease


It is frequently claimed that marijuana smoke contains such high concentrations of irritants that marijuana users' risk of developing lung disease is equal to or greater than that of tobacco users.

The Facts

Except for their psychoactive ingredients, marijuana and tobacco smoke are nearly identical. 21 Because most marijuana smokers inhale more deeply and hold the smoke in their lungs, more dangerous material may be consumed per cigarette. However, it is the total volume of irritant inhalation—not the amount in each cigarette—that matters.

Most tobacco smokers consume more than 10 cigarettes per day and some consume 40 or more. Regular marijuana smokers seldom consume more than three to five cigarettes per day and most consume far fewer. Thus, the amount of irritant material inhaled almost never approaches that of tobacco users.

Frequent marijuana smokers experience adverse respiratory symptoms from smoking, including chronic cough, chronic phlegm, and wheezing. However, the only prospective clinical study shows no increased risk of crippling pulmonary disease (chronic bronchitis and emphysema).

Since 1982, UCLA researchers have evaluated pulmonary function and bronchial cell characteristics in marijuana-only smokers, tobacco-only smokers, smokers of both, and non-smokers. Although they have found changes in marijuana-only smokers, the changes are much less pronounced than those found in tobacco smokers.

The nature of the marijuana-induced changes were also different, occurring primarily in the lung's large airways - not the small peripheral airways affected by tobacco smoke. Since it is small-airway inflammation that causes chronic bronchitis and emphysema, marijuana smokers may not develop these diseases. 22

In an epidemiological survey, approximately 1200 subjects gave information on smoking and pulmonary function at two-year intervals. A large percentage of the subjects underwent pulmonary function testing. Although a small group who reported previous marijuana smoking had significant pulmonary abnormalities, current marijuana smokers had no significant reduction in any pulmonary functions. 23

There are no epidemiological or aggregate clinical data suggesting that marijuana-only smokers develop lung cancer. However, since some bronchial cell changes appear to be pre-cancerous, an increased risk of cancer among frequent marijuana smokers is possible. 24

Since the pulmonary risks associated with marijuana are related to smoking, the danger is eliminated with other routes of administration. For committed smokers, pulmonary risk might be reduced with higher-potency products, which produce desired psychoactive effects with less inhalation of irritants. Smokers could also be encouraged to abandon deep inhalation and breath-holding, which increase drug delivery only slightly. Finally, pulmonary risk might be reduced if marijuana were smoked in water pipes rather than cigarettes. 25

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