Study: Early cannabis use during pregnancy does not indicate autism

Cannabis use during pregnancy has been increasing in the United States, and many people may be wondering what impact this trend might have on children. Some previous research has raised the possibility that prenatal cannabis exposure could increase the likelihood of having autistic children. However, a recent study – one of the largest ever conducted on cannabis and autism – found that exposure to cannabis in early pregnancy did not result in a higher likelihood of an autism diagnosis.

What is Autism?

Autism is classified as a developmental disorder. It influences the way individuals interact with others, communicate, learn, and experience life. One in 36 Americans is diagnosed with autism; Symptoms usually appear in the first two years of a person's life. Autism is also a spectrum disorder – it includes a variety of different symptoms that a person may experience and may require varying degrees of medical support.

Challenges that autistic people may face include a communication style that non-autistic people have difficulty understanding, sensory issues due to increased or decreased sensory perception, and more repetitive or restricted behavior patterns than non-autistic peers.

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While the medical literature classifies autism as a disorder, many autism advocates point out that many of the “symptoms” of autism are not inherently problematic or disordered; They simply clash with non-autistic expectations and result in autistic people being marginalized.

Previous research on cannabis exposure and autism

The recent study, conducted by researchers at Kaiser Permanente and UC San Francisco, examined whether cannabis use in early pregnancy could increase a woman's chances of giving birth to an autistic child. Autism has been linked to a variety of potential environmental causes, but most research suggests that genetics is the primary cause.

A study published in 2020 found a link between prenatal cannabis use and autism, leading to the question of whether cannabis use could cause autism. However, other studies found no connections. Unfortunately, these studies used self-report methods, which may have biased the results due to possible under-reporting of cannabis use.

Current Kaiser/UCSF researchers used more rigorous methods to determine whether prenatal cannabis use leads to higher rates of autism in children.

Studying prenatal cannabis and autism

This current study was one of the largest ever conducted on this topic (it included 178,948 pregnancies), but also used a more robust data set for cannabis use and autism.

This current study was one of the largest ever conducted on this topic (it included 178,948 pregnancies), but also used a more robust data set for cannabis use and autism. The study included information from Kaiser Permanente Northern California's integrated health system, which generally screens pregnant women for cannabis use through both self-report and urine toxicology testing. Kaiser also regularly screens and assesses children for autism.

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The researchers also included related factors in their analysis, such as sociodemographics, the additional medications and substances a mother uses, and general health status.

Prenatal cannabis use is not linked to autism

While an initial analysis appeared to suggest a link between autism and prenatal cannabis use, this link disappeared after factors such as sociodemographic characteristics and maternal health status were taken into account.

This lack of association suggests that mothers who use cannabis during pregnancy are more likely to have autistic children – not because of the cannabis itself, but because of other factors that also increase the likelihood of cannabis use.

Although researchers don't identify these specific factors, these results shouldn't be that surprising: For one thing, autism has a high rate of inheritance. Additionally, cannabis is sometimes used as an effective treatment for autism symptoms. Separate studies have found that autistic individuals tend to have lower levels of endocannabinoids in their bodies, which could indicate impairment of the endocannabinoid system.

Mothers with autism – or other conditions linked to the same genes as autism – are more likely to use cannabis and have autistic children; This connection could help explain the initial results of the study. But only further research will provide conclusive answers to these questions.

Limitations and future research

This study used a strong methodology with a large and diverse data set. However, the measurement was limited by the fact that cannabis consumption was only measured in early pregnancy. Future studies should measure cannabis use throughout pregnancy and ideally include information such as the methods and dosage of the cannabis itself.

Although this study suggests that prenatal cannabis use is not linked to autism, the authors still note that there is evidence that cannabis may affect development in other ways and should be avoided during pregnancy.