Cannabis use during pregnancy may increase a child鈥檚 risk of developing neurodevelopmental conditions such as autism and ADHD.
Up to 5 per cent of people in the US report using cannabis while pregnant, making it one of the most widely used recreational drugs during pregnancy. Yet we know relatively little about how this might affect fetal development.
To investigate further, at Curtin University in Australia and his colleagues collected data on more than 220,000 pregnant people in Australia between January 2003 and December 2005. About 1500 of them were diagnosed with a cannabis use disorder while pregnant. The researchers then tracked incidences of autism, ADHD and intellectual disability in the participants鈥� children over the next 14 years.
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After adjusting for factors like socioeconomic status, mental health conditions and use of other substances, the researchers found that children whose parent had a cannabis use disorder while pregnant had twice the risk of ADHD and autism compared with those born to participants who didn鈥檛. They also had a 46 per cent higher risk of intellectual disability and were more likely to be born prematurely and at a low birth weight.
The effects were even greater in children exposed to both cannabis and tobacco in pregnancy. On average, they had more than five times the risk of ADHD and nearly three times the risk of autism or intellectual disability than children who weren鈥檛 exposed to either substance in the womb.
鈥淭hese findings highlight the adverse impacts of prenatal cannabis exposure on offspring and have significant implications for public health interventions aimed at reducing prenatal substance use in general, but specifically cannabis use,鈥� says Tadesse, who presented the findings at the European Congress of Psychiatry in Hungary on 8 April.
However, more research is needed to understand why cannabis use in pregnancy would increase these developmental conditions, he says. Other studies have shown that a psychoactive compound in cannabis called tetrahydrocannabinol, or THC, can pass through the placenta and into the fetus鈥檚 brain, potentially affecting brain development.
THC and other cannabis compounds also act on receptors in a cell-signalling network known as the endocannabinoid system. Using cannabis in pregnancy could, therefore, affect how this system develops in children, potentially leading to neurodevelopmental conditions, says at the University of Washington in Seattle.
But other factors could also be behind the association of prenatal cannabis use and neurodevelopmental conditions. 鈥淢aternal cannabis use doesn鈥檛 occur in a vacuum,鈥� says Stoner. 鈥淲hen people develop substance use disorders, that might be in the context of dealing with significant stressors in their lives.鈥� This could include issues with housing or access to healthcare. 鈥淎ll of these things can affect fetal development,鈥� she says. This makes it hard to disentangle whether cannabis or some other factor in pregnancy is behind these findings.
