Pubdate: Tue, 25 Mar 2003
Source: New Scientist (UK)
Copyright: New Scientist, RBI Limited 2003
Contact:  http://www.newscientist.com/
Details: http://www.mapinc.org/media/294

MARIJUANA USE IN PREGNANCY DAMAGES KIDS' LEARNING

Children born to mothers who use marijuana during pregnancy may suffer a 
host of lasting mental defects, suggests a new study in rats. Marijuana is 
the most widely used illegal drug among women of reproductive age.

The offspring of pregnant rats given a low dose of cannabinoid were found 
to perform poorly in learning tests throughout their lives, compared to 
rats that were not exposed.

The Italian research team found that long-term learning in the rats was 
damaged by the cannabinoids irreversibly disrupting chemical and electrical 
processes in the brain during gestation. The exposed rats were also more 
hyperactive as infants, although this effect wore off as the rats reached 
adulthood.

Vincenzo Cuomo, at the La Sapienza University in Rome, and colleagues 
suggest that similar brain effects could explain learning problems in 
children born to mothers who use the soft drug during pregnancy.

"This is absolutely relevant," says Peter Fried, a psychologist at Carleton 
University in Ottawa, Canada, who has done similar work in humans. "What 
they have found is very consistent with what we have found in humans."

Confounding Factors

The possible effects of maternal marijuana use on the unborn child and the 
child's later behaviour are controversial, say Cuomo and colleagues. They 
argue that rat studies can be very useful in assessing human effects, 
because studies of people can be hampered by complex confounding factors. 
These could include cigarette smoking, wealth or urban living.

In the study, pregnant rats were injected with a low dose of an artificial 
cannabinoid. Offspring exposed to the drug during gestation showed 
hyperactivity during infancy and adolescence, as measured by how many times 
they broke infrared beams crisscrossing their cages.

This stopped when they reached adulthood, but was replaced by problems with 
memory retention. The researchers showed reduced levels of a messenger 
chemical called glutamate in the hippocampus, part of the brain associated 
with learning and visual ability. They also found disruption of electrical 
processes associated with learning in this region.

Fried told New Scientist that as well as affecting memory and learning, 
exposure to marijuana during pregnancy has a strong effect on visual 
mapping and analysis in human children.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 
10.1073/pnas.0537849100)
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