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Children of moms who use weed during pregnancy more prone to anxiety

"...Some people use cannabis to reduce anxiety and relax. But our study shows exposure to cannabis in the womb has the opposite effect on children."

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By Mark Waghorn via SWNS

Children of mothers who smoke or vape cannabis during pregnancy are more likely to develop stress and anxiety, warns new research.

They are also prone to aggressive behavior and hyperactivity, say scientists.

The discovery adds to evidence marijuana can harm a baby's development in the womb.

It is the most widely taken drug by women of reproductive age - often to relieve stress and anxiety.

Cannabis use among pregnant women has become more common, doubling over the last two decades.

Senior author Dr, Yasmin Hurd, director of the Addiction Institute at Mount Sinai, New York, said: "Pregnant women are being bombarded with misinformation that cannabis is of no risk.

"The reality is it's more potent today than it was even a few years ago. Our findings indicate using it during pregnancy can have long-term impacts on children."

Portrait of woman smoking with electronic cigarette
Children whose mothers used cannabis during pregnancy showed higher anxiety, aggression and hyperactivity (Shutterstock)

They were based on 322 mother-child pairs in New York City drawn from a study of stress in pregnancy that has been ongoing since 2009.

When they were about six, children whose mothers used cannabis during pregnancy showed higher anxiety, aggression and hyperactivity.

They also had higher levels of the stress hormone cortisol - compared to children of non-cannabis users.

Maternal cannabis use was also linked with poorer heart rate variability, the change in time between heartbeats - reflecting increased sensitivity to stress.

Analysis of placental tissue collected at the time of birth also identified fewer immune-activating genes - predicting higher anxiety.

Cannabinoids, the active agents in cannabis, can be transferred from the mother to the offspring through the placental blood.

First author Professor Yoko Nomura, of the City University of New York, said: "We know cannabinoid signalling plays a role in modulating stress, which is why some people use cannabis to reduce anxiety and relax.

"But our study shows exposure to cannabis in the womb has the opposite effect on children.

"It causes them to have increased levels of anxiety, aggression and hyperactivity compared to other children who were not exposed to cannabis during pregnancy."

Hormone levels, including cortisol released during stress, were measured via the children's hair samples.

Heart function was measured using electrocardiogram recordings as they were subjected to minor stress.

A burst of startling loud tones interrupted their viewing of a calm video as they sat with their parents.

Behavioral and emotional functioning was also assessed based on surveys administered to the parents.

Legalization of cannabis is spreading across the world. Many people "mistakenly believe" its use is without significant health risks.

In line with softening public opinion, it has emerged as one of the most consumed recreational drugs of abuse during pregnancy.

Yet the impact of maternal cannabis use on foetal and childhood development is not clear, said the researchers.

Hurd said: "The study results underscore the need for non-biased education and outreach to the public and particularly vulnerable populations of pregnant women regarding the potential impact of cannabis use.

"Disseminating this data and accurate information is essential to improving the health of women and their children."

In September, a study of 11,500 US children found those whose mothers took it while pregnant were vulnerable to psychosis and sleep problems.

Earlier this year a study in Canada found exposure to the drug in the womb doubles the risk of autism.

Previous research has suggested exposure to cannabis in the womb causes learning and physical activity difficulties in children.

Brain receptors that trigger the behavioural effects of cannabis have been found to be present in rat brains during prenatal development.

Cannabinoids can be transferred from the mother to the offspring through the placental blood during gestation both in humans and in rodents.

Other studies have indicated cannabis taken during pregnancy affects the cognitive development of the unborn child - particularly memory.

Cannabis use among pregnant women has doubled over the last two decades.

The UK's National Health Service says: "Cannabis use may affect fertility. Regular or heavy cannabis use has been linked to changes in the female menstrual cycle and lower sperm count, or lower sperm quality in men.

"Using cannabis while pregnant may harm the unborn baby. Cannabis smoke contains many of the same harmful chemicals found in cigarette smoke.

"Regularly smoking cannabis with tobacco increases the risk of a baby being born small or premature.

"Cannabis has not been linked to birth defects, but research suggests that using cannabis regularly during pregnancy could affect a baby's brain development as they get older."

The findings were published in Proceedings of the National Academy of Sciences.

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