Drug Watch International

MARIJUANA RESEARCH REVIEW  

Damaging effects of prenatal marijuana use show up in older children

Subjects of this investigation by Fried PA, reporting on the effects of marijuana used during pregnancy since 1978 (Life Sciences, 56:2159-2168,1995), were primarily middle class, low-risk women who entered the study in their early pregnancy. The offspring have been assessed repeatedly during the neonatal period and at least annually up unto the age of 6. While earlier reports of children to age 3 did not reveal an association between defects associated with in utero exposure to marijuana (memory, language development, visual perceptual functioning), later follow-up could distinguish between marijuana exposed children and control children.

Prenatal marijuana exposure showed that at age 4 and older children showed increased behavioral problems and decreased performance on visual perceptual tasks, language comprehension, sustained attention and memory. The author concluded that the nature and the timing of the appearance of these deficits were consistent with the notion that prenatal marijuana exposure adversely affected behavior that is goal-directed which includes planning, organized search, and impulse control. These findings suggested to the author that chronic marijuana use impacted on functioning of the prefrontal lobe in the brain.

Commentary: This study documents that the adverse effects of prenatal exposure may not become apparent until the child grows old enough to perform high level tests such as those termed "executive functioning." The danger of drawing short-term conclusions from effects that, while introduced in utero may take a generation to discover, have been amply documented for other poisons ingested by expectant mothers such as lead, cocaine, and alcohol. Some authors have suggested that differences in the functioning of children exposed in utero to marijuana to non-exposed children often disappear by age 2-3. However, effects of marijuana cannot be determined until enough time has passed so that the children are expected to perform. Then, and only then, can their performance be accurately assessed. This prospective study provides valuable insights into the many insidious problems associated with the use of marijuana. ##

Prenatal use of tobacco and marijuana by adolescent mothers causes increased damage to infants

Cornelius et al. studied the effects of tobacco and marijuana use during pregnancy on length of gestation, growth, and formation of 310 children of adolescent mothers (Pediatrics 95:738-743). The subjects were interviewed at mid-pregnancy and after delivery to obtain information on their use of tobacco, marijuana, and other substances before and during pregnancy. The infants were examined by physicians 24-36 hours after birth. The average maternal age was 16.

Prenatal tobacco use was associated with reduced birthweight, length, and circumferences of head and chest, but not the gestational age or the number of physical abnormalities of the baby. Prenatal marijuana smoking was associated with increased premature birth. Additionally, some physical abnormalities were associated with the use of marijuana during the first trimester among the white participants in the study. These effects of prenatal tobacco and marijuana smoke were prominent despite the lower levels of exposure in these offspring as compared with the offspring of mothers of adult age. The authors concluded that the risk of adverse effects from use of tobacco or marijuana during pregnancy may be increased for offspring of adolescent mothers.

Commentary: Under the best of circumstances, infants of adolescent mothers are 2-6 times more likely to be of low birthweight compared to infants of adult women, and these infants are at increased risk for prematurity, complications, and infant mortality. During the first year of life, the mortality of children born to teenagers is 2-3 times that of infants born to older mothers, and there is a 64:1 increase of Sudden Infant Death Syndrome, Hectman L. Teenage mothers and their children: risks and problems: A review, Canadian Journal of Psychiatry, 34:569-575,1989. The current study points out that the use of tobacco or marijuana can be associated with adverse effects on newborns. The authors found that adolescent mothers who smoked tobacco during pregnancy were more likely to binge on alcohol and use other illicit drugs in the first trimester. Mothers who smoked heavily had significantly lower pre-pregnancy weight. Similarly, teenagers who used marijuana tended to use more tobacco and drink more alcohol, particularly in the crucial first trimester when the fetal organs are being formed. It is clear that preventive efforts aimed at eliminating the use of marijuana and tobacco would correlate with reduction of alcohol intake, further reducing the risk of adverse effects to the children of these adolescent mothers. ##

Attention impaired by marijuana use  

If attention processes were impaired through chronic use of marijuana, this would be important to understanding decreases in work performance, memory learning, and every day tasks, such as driving. Previous research has shown that cannabis use impairs attention while the user is intoxicated, but the long-term effects of chronic use had not previously been studied. Subjects in this study by Solowji et al (Biol Psychiatry, 37:731-739,1995) were recruited from the general community through advertising. The minimum requirement for participation as a cannabis user was regular use at least once a month for 3 years. By criteria established by the American Psychiatric Association, all subjects could be labeled as cannabis-dependent or cannabis abusers. The control group of non-users was selected to cover the range of the age, years of education, and sex distribution in the user group. The subjects were excluded if they had a history of any psychiatric or neurologic disorders, head injury, or the use of any other drugs more than once a month, or alcohol abuse. The ability to focus attention and filter out irrelevant information was measured and was found to be impaired progressively by the number of years of marijuana use, but was unrelated to the frequency of use. With increasing frequency of use the speed of information processing was delayed significantly but was unaffected by the duration of use. The results suggested that a chronic build-up of cannabinoid produces both short- and long-term impairments of brain function compared to control subjects.

Commentary: The data from this well-done study provide an outstanding demonstration that marijuana use effects brain function, and documents in an objective way what has been observed for decades, namely that marijuana produces an attention deficit. This study was controlled for alcohol use, educational level, and l.Q. scores. No subject involved in other illicit drug activity was included in the sample so that these data are from individuals who consume marijuana by smoking alone. The data developed in this study provide evidence that increasing duration of cannabis use leads to progressively impaired information processing which could lead to distractibility and impairment in any situation where concentration and focus attention are essential. ##  

Passive exposure to cocaine and marijuana impacts children

In a study by Bhushan et al (American Journal of Public Health, 84:675-686,1994) over 7,700 infants and young children visiting the pediatric emergency room of a New York City hospital for six months in 1992 were screened for evidence of byproducts of marijuana and cocaine in their urine. Of the approximately 15% who were given a routine urinalysis 245 were randomly selected for further testing. The criteria recommended by NIDA for testing exposure to drugs were applied in 100 of the cases and no metabolites were detected. However, when more sensitive measures for cocaine and marijuana byproducts were used to test the remaining 145 specimens, 11% tested positive for cocaine or marijuana metabolites. Since these children were all age 8 and under, the most likely avenue of ingestion is by passive exposure to smoked forms of the drugs. There is some indication that passive low level exposure may be cumulative in children.

Commentary: Low level exposures to toxins in the environment can only be detected by changing the detection threshold to a highly sensitive, but still specific level. This study shows that use of NIDA limits for exposure would not have picked up the passive exposure of children whose mothers use smoked marijuana and cocaine in their presence. Symptoms consistent with cocaine toxicity have been described previously in infants and toddlers exposed to smoke of cannabinoids and free base cocaine, by Moreland, et al., Journal of Forensic Sciences 30:997-1002,1985. Though these children have no substance use problems themselves their exposure may predisposed them to such problems in the future as well as other negative physiological consequences. ##

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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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