Prenatal Cannabis Co-Exposure With Tobacco Had Mixed Effects on Children's Attention and Memory

Prenatal tobacco exposure was associated with increased impulsive responding on sustained attention tasks, particularly when exposure occurred in the first trimester. Surprisingly, children co-exposed to both tobacco and cannabis showed higher short-term memory scores than non-exposed children. Cannabis co-exposure did not exacerbate the attention deficits seen with tobacco alone.

Longitudinal cohort study recruiting participants in the first trimester of pregnancy. Children (n=133) were assessed at ages 9-12 on sustained attention, attentional set shifting, and working memory tasks. Three groups were compared: non-exposed (n=34), tobacco-only (n=37), and tobacco-cannabis co-exposed (n=62).

Most studies examine cannabis or tobacco exposure separately. This study directly compares the effects of combined exposure, finding that cannabis does not appear to add to tobacco's neurodevelopmental impact on attention. The unexpected memory finding highlights how complex prenatal exposure effects can be.

The finding that cannabis co-exposure did not worsen tobacco-related attention deficits challenges assumptions about cumulative prenatal substance harm. The perplexing memory finding may reflect selection effects, resilience factors, or genuine neurodevelopmental complexity.

Small sample size, particularly for the non-exposed group (n=34). Could not isolate cannabis-only exposure effects. Oversampled for co-exposure, which may limit generalizability. The unexpected memory finding needs replication before drawing conclusions.