Large study found no link between prenatal cannabis use and child autism | Research

The takeaway

In nearly 179,000 pregnancies, maternal cannabis use in early pregnancy was not associated with child autism spectrum disorder after adjusting for maternal characteristics, contradicting some earlier studies.

Pregnant individuals, pediatricians, autism researchers, cannabis policy makers

Adjusted HR 1.05 (not significant)

What the researchers found

After adjustment for maternal characteristics, prenatal cannabis use was not associated with child ASD (HR 1.05, 95% CI 0.84-1.32). No dose-response relationship was observed. No sex-specific associations were found (males: HR 1.01; females: HR 1.19).

Why it matters

A previous meta-analysis found a 30% increased ASD risk with prenatal cannabis exposure, but this larger, well-controlled study found no association after adjusting for confounders, suggesting earlier findings may have been driven by unmeasured variables.

The numbers in context

178,948 pregnancies. 8,486 (4.7%) screened positive for cannabis. ASD diagnosed in 3.6% of children. Adjusted HR: 1.05 (95% CI 0.84-1.32). Males HR: 1.01. Females HR: 1.19.

How the study worked

Population-based retrospective birth cohort of 178,948 singleton pregnancies among 146,296 Kaiser Permanente Northern California members (2011-2019). Cannabis use screened via self-report and urine toxicology at ~8-10 weeks gestation. ASD identified by ICD-10 codes from EHR.

What this study cannot tell us

Cannabis use assessed only at early prenatal care entry. Cannot rule out effects of use later in pregnancy. EHR-based ASD diagnosis may differ from research-standard assessment. Children born 2019 had limited follow-up time for ASD diagnosis.

How to read the evidence

Large population-based cohort with objective screening and confounder adjustment provides strong evidence, though limited to early-pregnancy exposure.

When this study was published

2024 study of Kaiser Permanente data from 2011-2019

The bigger picture

The contrast between this null finding and earlier positive associations underscores how important confounding adjustment is in observational cannabis research. Maternal characteristics that predict both cannabis use and ASD risk (mental health, other substance use) may drive apparent associations.

Questions still open

Why do some studies find a cannabis-ASD link while this one does not? Is the difference primarily about confounding adjustment? Would studies of heavier or later-pregnancy use find different results?

Common questions

Does this contradict studies linking cannabis to autism?

Partially. Earlier studies, including a meta-analysis, found associations, but this larger study with better confounding adjustment found none. The difference may be that earlier studies did not fully account for maternal characteristics that predict both cannabis use and ASD risk.

Should pregnant people stop worrying about cannabis and autism?

The study found no ASD link specifically, but prenatal cannabis is still associated with other adverse outcomes. The authors recommend clinicians continue advising against use during pregnancy.

Read the original research

Maternal Prenatal Cannabis Use and Child Autism Spectrum Disorder.

JAMA network open, 7(10), e2440301

View on PubMed ↗Publisher’s paper ↗

Citation

Avalos, Lyndsay A; Shenkute, Mahlet; Alexeeff, Stacey E; Oberman, Nina; Croen, Lisa A; Davignon, Meghan; Adams, Sara R; Ansley, Deborah; Castellanos, Carley; Young-Wolff, Kelly C. (2024). Maternal Prenatal Cannabis Use and Child Autism Spectrum Disorder.. JAMA network open, 7(10), e2440301. https://doi.org/10.1001/jamanetworkopen.2024.40301