Researchers have stumbled on yet another surprising effect of marijuana: smoking cannabis during pregnancy produced New Zealand children who scored better on one measure of brain development.

The team from University of Auckland, publishing their findings Nov. 19 in the journal Nature: Scientific Reports, investigated the effects of fetal exposure to recreational drugs, particularly the visual areas of the brain.

They found that prenatal cannabis benefitted global motion perception, a biomarker of visual neurodevelopment, in preschoolers – the cannabis-exposed kids were nearly 50 percent better at this than others. Drinking alcohol, on the other hand, impaired this measure.

Study author Arijit Chakraborty reported that exposure to both marijuana and alcohol had no effect, which suggested that the former cancelled out the harm from the latter. Further, there was no difference in global motion perception between kids exposed to both cannabis and alcohol and kids without drug exposure.

Prenatal exposure to methamphetamine, too, was seen to have no influence on vision. Overall drug exposure did not affect other related functions such as visual acuity.

The team measured global measure perception – a test involving specific visual brain areas – in 145 preschoolers age 4 1/2, all exposed to various mixes of the substances prior to birth, and 25 unexposed kids.

The drugs detected on the first group were marijuana on 40 percent, alcohol on 56.4 percent, methamphetamine on 44.2 percent, and nicotine on 75.2 percent. The majority of kids, or 81.3 percent, had multiple drug exposure.

“[T]he effects [on visual development] are dependent on the specific drugs used during pregnancy,” said Chakraborty, who proposed considering their findings in preventing the effects of fetal alcohol syndrome.

Fetal Alcohol Network’s Christine Rogan said that the dangers of alcohol intake during pregnancy have been established “for an awfully long time.”

“We know that of all drugs alcohol appears to be the most harmful; none of them are good,” she argued, adding that the amount of alcohol taken today has been normalized to the point that pregnant females do not realize they are drinking too much.

The research team said that they are not recommending mothers to start smoking marijuana, given previous findings that it had ill effects on other areas of neurodevelopment.

"We would recommend the mothers to stop drinking in the first place instead of trying marijuana unless subsequent research specifically answers this question,” said Chakraborty, who believed the results may also be relevant in the Indian setting given the prevalence of smoking and drinking among elite Indian women.

Photo: Torben Hansen | Flickr

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