Meta-analysis found prenatal cannabis may slightly raise ADHD risk but not autism in offspring | Research

The takeaway

A meta-analysis of 534,445 participants found prenatal cannabis exposure slightly elevated ADHD risk (OR 1.13) and offspring cannabis use (OR 1.20), but was not associated with autism, psychosis, anxiety, or depression.

Pregnant individuals, obstetricians, developmental psychiatry researchers

ADHD OR 1.13; ASD not significant

What the researchers found

After adjusting for confounders, pooled ORs: ADHD 1.13 (95% CI 1.01-1.26); ASD 1.04 (0.74-1.46, not significant); psychotic symptoms 1.29 (0.97-1.72, not significant); anxiety 1.34 (0.79-2.29, not significant); depression 0.72 (0.11-4.57, not significant); offspring cannabis use 1.20 (1.01-1.42).

Why it matters

This is the most comprehensive meta-analysis of prenatal cannabis and long-term neuropsychiatric outcomes. The small but significant ADHD association and the null findings for ASD, psychosis, anxiety, and depression help clarify a confusing literature.

The numbers in context

18 studies, 534,445 participants. ADHD OR: 1.13 (1.01-1.26). ASD OR: 1.04 (0.74-1.46). Psychotic symptoms OR: 1.29 (0.97-1.72). Offspring cannabis use OR: 1.20 (1.01-1.42). Anxiety and depression: not significant.

How the study worked

PRISMA and MOOSE-compliant systematic review searching MEDLINE, EMBASE, and Cochrane through January 2024. 18 observational studies included (534,445 participants). Random-effects meta-analysis with confounder adjustment.

What this study cannot tell us

All observational studies with potential residual confounding. Small effect sizes near the null. Limited studies for some outcomes (depression: few studies). Cannot account for increasing cannabis potency over time. Exposure measurement varies across studies.

How to read the evidence

Large PRISMA-compliant meta-analysis with confounder adjustment provides strong evidence synthesis, though individual study quality varies.

When this study was published

2024 meta-analysis searching databases through January 2024

The bigger picture

The finding that offspring of cannabis-exposed pregnancies were 20% more likely to use cannabis themselves raises questions about whether this reflects genetic heritability, in utero neurobiological priming, or shared environmental factors.

Questions still open

Is the ADHD association causal or driven by unmeasured confounders? Does increasing cannabis potency mean future pregnancies will show larger effects? Why does prenatal exposure predict offspring cannabis use?

Common questions

Does prenatal cannabis cause ADHD?

The meta-analysis found a small increased risk (13%), which was statistically significant. However, the effect size is small and could partly reflect unmeasured confounders. The authors note caution is warranted but call for more research.

Does prenatal cannabis cause autism?

This meta-analysis found no significant association between prenatal cannabis and ASD (OR 1.04), contradicting some individual studies that reported positive associations.

Read the original research

Prenatal cannabis exposure and the risk for neuropsychiatric anomalies in the offspring: a systematic review and meta-analysis.

American journal of obstetrics and gynecology, 231(6), 574-588.e8

View on PubMed ↗Publisher’s paper ↗

Citation

Bassalov, Hely; Yakirevich-Amir, Noa; Reuveni, Inbal; Monk, Catherine; Florentin, Sharon; Bonne, Omer; Matok, Ilan. (2024). Prenatal cannabis exposure and the risk for neuropsychiatric anomalies in the offspring: a systematic review and meta-analysis.. American journal of obstetrics and gynecology, 231(6), 574-588.e8. https://doi.org/10.1016/j.ajog.2024.06.014