Smoking during pregnancy raises children’s mental health risk

by · News-Medical

MSDP and mental health

Mothers share common genetic and environmental influences with their offspring. This explains in part the externalizing symptoms associated with MSDP. However, internalizing and externalizing symptoms are often highly correlated, especially in adolescence.

MSDP may not be specifically associated with externalizing symptoms; rather, MSDP might predispose to mental ill-health, or contribute to both externalizing and internalizing symptoms. A single sibling study suggests that externalizing symptoms are more common with MSDP.

Externalizing versus internalizing symptoms

Externalizing and internalizing symptoms refer to the expression of mental ill-health. The former includes outwardly directed behaviors such as aggression, hyperactivity, and rule-breaking. Internalizing behaviors are inward-facing, such as anxiety, depression, or social withdrawal.

These symptom types appear at different ages. Externalizing symptoms tend to appear earlier and occur more often in boys. Internalizing symptoms appear more commonly in adolescence and affect more girls than boys. However, consistent developmental patterns have not been observed for either type or across sexes.

In addition, multiple studies suggest that male fetuses are more likely to be adversely affected by MSDP throughout development. MSDP is also linked to higher externalizing behaviors within the same child over time. This motivated the authors to search for MSDP-sensitive developmental windows.

Disentangling MSDP-associated mental health symptoms

To better understand how prenatal smoking relates to different types of mental health problems, the researchers applied the severity–directionality model of psychopathology, a framework designed to separate overall symptom burden from the balance of symptom types.

In this model, severity reflects the total level of psychopathology across both internalizing and externalizing domains, capturing the extent of comorbidit, since higher severity scores typically indicate the presence of both types of symptoms simultaneously. In contrast, directionality captures the relative predominance of one symptom type over the other, indicating whether an individual’s profile leans more toward internalizing problems, such as anxiety or depression, or toward externalizing behaviors like aggression or hyperactivity, regardless of total symptom load.

This approach allows researchers to move beyond traditional analyses that examine internalizing and externalizing symptoms separately, enabling a more precise assessment of whether MSDP is associated with general mental health risk, domain-specific effects, or both.

MSDP predicts more severe symptoms

Across all age groups examined in two-year intervals, maternal smoking during pregnancy was consistently associated with higher overall symptom severity, indicating greater comorbid mental health burden among exposed children. Importantly, these associations remained statistically significant even after adjusting for a wide range of potential confounders, including sociodemographic factors, family psychiatric history, other prenatal substance use, and postnatal smoke exposure.

When examining sex differences, the findings were largely similar for boys and girls. One exception emerged in the 13–14-year age group, where associations with symptom severity appeared stronger in boys, though this pattern was not observed in other age bins and should therefore be interpreted with caution, particularly given variability in sample sizes.

No age or sex differences

Overall, the findings showed consistency across developmental stages, with similar patterns of association observed from early childhood through adolescence. While the study was designed to detect potential age- or sex-specific effects, there was little evidence of strong or systematic differences across age groups or between boys and girls.

Although certain analyses hinted at possible variation, such as slightly stronger effects in early childhood or early adolescence, these patterns were not robust and often attenuated when additional covariates were included or when sample sizes were reduced. As a result, the findings do not provide strong evidence for clearly defined sensitive developmental periods during which MSDP exerts a uniquely heightened effect.

Instead, the results suggest that the impact of prenatal smoking on mental health may be broadly distributed across development, reinforcing the importance of prevention efforts aimed at reducing maternal smoking during pregnancy rather than targeting specific postnatal intervention windows.

Strengths and limitations

The study has some limitations, such as self-reported MSDP data and a lack of data on the timing and frequency of smoking in the prenatal period. The psychopathology scoring system used here could not be confirmed as measurement-invariant across age groups, limiting direct comparisons across age and sex categories.

Again, symptom severity is more strongly linked to the transmission of psychopathology across generations, rather than of the actual type of symptom across generations: externalizing versus internalizing. Thus, this study might have overestimated the risk of symptom severity from MSDP alone by not incorporating risk attributable to life stress and genetic factors, suggesting the findings should not be interpreted as strictly causal.

Still, this study used a large, sociodemographically diverse sample, improving its generalizability and enabling the detection of small associations.

Implications

These findings suggest that MSDP is linked with increased severity of multiple types of mental health symptoms in the offspring.

They also indicate a greater tendency to externalize problems across multiple developmental periods rather than a single age group. However, the other age categories had much smaller sample sizes, suggesting that while some patterns may hint at differences across developmental stages, there is no strong or consistent evidence for clear MSDP-sensitive periods. Rather, it is important to discourage MSDP and thus prevent prenatal exposure.

In addition, interventions should broadly target at-risk children until adulthood, rather than being applied to critical periods.

The occurrence of internalizing symptoms may primarily reflect the higher risk of comorbidity with MSDP, whereas externalizing problems may reflect both general severity and some degree of domain-specific risk. “This indicates that there are multiple pathways from MSDP to psychopathology symptoms in childhood and adolescence.”

While offering a novel viewpoint on pediatric neurodevelopment, it suggests the importance of reducing MSDP to minimize the risk of associated mental health disorders in children.

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