Prenatal Cigarette Exposure Hurt Children's Reading and Language, but Prenatal Marijuana Did Not | Research

The takeaway

Among 131 children aged 9-12 followed from birth, prenatal cigarette exposure was linked to lower reading and language scores in a dose-dependent pattern, while prenatal marijuana exposure showed no significant relationship to either outcome.

Read this if you want to understand how prenatal cannabis exposure compares to prenatal tobacco exposure on children's cognitive development.

Prenatal marijuana exposure was not significantly related to reading or language outcomes

What the researchers found

Researchers examined reading and language abilities in 131 children aged 9-12 who were part of a longitudinal study tracking prenatal drug exposure from a predominantly middle-class population.

Prenatal cigarette exposure showed a dose-dependent association with lower language and reading scores, even after controlling for potential confounders. The effects were strongest on auditory-related aspects of reading, consistent with earlier findings linking prenatal cigarette exposure to altered auditory functioning.

Prenatal marijuana exposure was not significantly related to either reading or language outcomes at this age.

An additional finding: while the mother's own passive smoke exposure during pregnancy did not affect outcomes, the child's postnatal secondhand smoke exposure was associated with poorer language scores.

Why it matters

This study provided important comparative data: prenatal cigarette exposure, not marijuana exposure, was the substance linked to cognitive effects in this age group. The finding has implications for risk communication to pregnant women and for understanding which prenatal exposures carry the greatest developmental risk.

The numbers in context

131 children aged 9-12. Prenatal cigarette exposure: dose-dependent association with lower reading and language. Prenatal marijuana exposure: not significantly related to outcomes. Postnatal secondhand smoke: associated with poorer language scores.

How the study worked

Longitudinal study of 131 children aged 9-12 from a low-risk, predominantly middle-class sample. Prenatal exposure to marijuana and cigarettes was ascertained prospectively. Reading and language were assessed using multiple measures. Discriminant Function Analysis controlled for potential confounders.

What this study cannot tell us

Predominantly middle-class sample may not generalize to higher-risk populations. The absence of a significant marijuana association does not prove safety, as the study may have been underpowered to detect small effects. Self-reported prenatal substance use may be inaccurate.

How to read the evidence

A longitudinal cohort study with prospective exposure assessment and confounder control. Good design but moderate sample size and a single developmental window.

When this study was published

Published in 1997. Subsequent studies from this and other cohorts have continued to track prenatal cannabis exposure effects through adolescence.

The bigger picture

This study is part of a larger longitudinal project that has followed children prenatally exposed to cannabis from birth through adolescence. While prenatal marijuana exposure has been linked to some subtle effects at other ages, the reading and language domain at ages 9-12 did not appear to be affected.

Questions still open

Would larger samples or different cognitive measures detect prenatal marijuana effects? Do effects emerge at later ages as cognitive demands increase? How do prenatal cigarette and marijuana effects interact in combined users?

Common questions

Does smoking marijuana during pregnancy affect the child's reading?

In this study, prenatal marijuana exposure was not significantly related to reading or language outcomes in children aged 9-12. Prenatal cigarette exposure, by contrast, was associated with lower scores.

Does this mean marijuana is safe during pregnancy?

Not necessarily. This study measured specific outcomes at specific ages. Other studies have found subtle effects of prenatal cannabis exposure on other cognitive domains or at different ages.

Read the original research

Reading and language in 9- to 12-year olds prenatally exposed to cigarettes and marijuana.

Neurotoxicology and teratology, 19(3), 171-83

View on PubMed ↗

Citation

Fried, P A; Watkinson, B; Siegel, L S. (1997). Reading and language in 9- to 12-year olds prenatally exposed to cigarettes and marijuana.. Neurotoxicology and teratology, 19(3), 171-83.