Both maternal and paternal cannabis use during pregnancy were linked to psychotic-like experiences in children at age 10 | Research

The takeaway

In a birth cohort of 3,692 children, both maternal cannabis use (38% higher risk) and paternal cannabis use (44% higher risk) during pregnancy were associated with more psychotic-like experiences at age 10, suggesting genetic rather than direct prenatal exposure effects.

Read this if you are a parent who used cannabis and want to understand the risk factors for your children's mental health.

Paternal cannabis use (44% increase) predicted child psychosis risk as much as maternal use (38%)

What the researchers found

Researchers followed 3,692 children from the Generation R birth cohort to examine whether parental cannabis use during pregnancy affected the risk of psychotic-like experiences at age 10. They used a clever study design: comparing maternal versus paternal cannabis use to disentangle direct prenatal exposure effects from shared genetic/familial factors.

Maternal cannabis use during pregnancy was associated with a 38% increase in offspring psychotic-like experiences. But critically, paternal cannabis use during pregnancy showed a nearly identical association (44% increase), even though fathers do not directly expose the fetus.

Furthermore, maternal cannabis use exclusively before pregnancy (but not during) showed similar associations to continued use during pregnancy, suggesting the timing of exposure mattered less than the fact that the parent used cannabis.

This pattern strongly suggests that shared genetic vulnerabilities or familial factors, rather than direct chemical exposure of the fetus to cannabis, largely explain the association between parental cannabis use and offspring psychotic-like experiences.

Why it matters

This study provides a more nuanced understanding of why children of cannabis-using parents may develop psychotic-like experiences. Rather than cannabis directly damaging the developing fetus, the finding that paternal use shows the same association points to shared genetics and family environment as the primary pathway. This has implications for how we counsel families and design prevention strategies.

The numbers in context

3,692 participants from Generation R cohort. Maternal cannabis use: adjusted OR = 1.38 (95% CI 1.03-1.85). Paternal cannabis use: adjusted OR = 1.44 (95% CI 1.14-1.82). Pre-pregnancy-only maternal use showed comparable estimates to continued use during pregnancy. Offspring assessed at age 10.

How the study worked

This prospective cohort study was embedded in the Generation R birth cohort (N = 3,692). Maternal cannabis exposure was verified using both self-reports and urine cannabis metabolite levels. Paternal cannabis use was reported by mothers. Offspring psychotic-like experiences were assessed at age 10. Adjusted odds ratios were calculated controlling for confounders.

What this study cannot tell us

Psychotic-like experiences at age 10 are subclinical and may not develop into psychotic disorders. Paternal cannabis use was reported by mothers, which may be less accurate than direct reporting. The study cannot completely rule out indirect paternal effects (secondhand smoke exposure, parenting behavior). Self-reported cannabis use may underestimate actual use.

How to read the evidence

This is a large prospective birth cohort with verified maternal exposure and clever paternal comparison design, providing moderate evidence for shared genetic mechanisms.

When this study was published

Published in 2018. The Generation R cohort continues to produce follow-up data on these children.

The bigger picture

This study reframes the cannabis-psychosis link from a purely environmental exposure narrative to one involving shared genetic vulnerability. The fact that a father's cannabis use during the pregnancy period predicts offspring psychosis risk as strongly as the mother's direct fetal exposure is a powerful argument for genetic confounding in the cannabis-psychosis literature.

Questions still open

What specific genetic variants are shared between cannabis use propensity and psychosis vulnerability? Does the finding that paternal use shows similar risk change how prenatal cannabis counseling should be framed? Will children with psychotic-like experiences at 10 develop clinical psychosis later?

Common questions

Does cannabis use during pregnancy cause psychosis in children?

This study found that parental cannabis use was associated with more psychotic-like experiences in children, but the fact that paternal use (which doesn't directly expose the fetus) showed the same association suggests shared genetics rather than direct fetal harm are the main explanation.

Should fathers stop using cannabis during pregnancy?

While this study cannot prove that paternal cannabis use directly harmed children, it does show that families where either parent uses cannabis have higher rates of offspring psychotic-like experiences. This likely reflects shared genetic vulnerabilities that warrant awareness and monitoring.

Read the original research

Maternal and paternal cannabis use during pregnancy and the risk of psychotic-like experiences in the offspring.

Schizophrenia research, 202, 322-327

View on PubMed ↗Publisher’s paper ↗

Citation

Bolhuis, Koen; Kushner, Steven A; Yalniz, Selda; Hillegers, Manon H J; Jaddoe, Vincent W V; Tiemeier, Henning; El Marroun, Hanan. (2018). Maternal and paternal cannabis use during pregnancy and the risk of psychotic-like experiences in the offspring.. Schizophrenia research, 202, 322-327. https://doi.org/10.1016/j.schres.2018.06.067