The association between prenatal exposure to cannabis with and without tobacco and early cognitive and language development in a sample of polysubstance-exposed children

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BACKGROUND: Prenatal cannabis exposure may have adverse effects on development which could be amplified by co-exposure with tobacco. OBJECTIVE: This study examined whether prenatal cannabis exposure was associated with disrupted language or cognitive development, and whether co-exposure to tobacco was associated with worse outcomes than to cannabis alone. METHODS: In this historical cohort study, we compared children from the Danish Family Outpatient Clinics who had prenatal exposure to cannabis (n = 106), tobacco (n = 138), cannabis and tobacco (n = 112), or no exposure to either drug (control group, n = 454) on the Bayley-III Language and Cognitive scales at 1-58 months of age (99.7% at ≤36 months). Roughly half were tested at multiple ages, yielding 1362 language assessments (49.2% tested ≥ twice) and 1549 cognitive assessments (53.6% tested ≥ twice). Most children had additional prenatal exposure to other drugs (49.8%), including the control group (63.9%). Scores were investigated in linear mixed models with factors Exposure Group, Age, and Exposure Group ∗ Age, and covariates alcohol exposure, other drug exposure, maternal medical diagnoses, and maternal education. RESULTS: Children with prenatal cannabis exposure scored significantly higher on the Language scale compared with controls (3.26 points; 95% CI = 0.26-6.26). There was a positive association between Language scores and age at assessment for children with cannabis and tobacco exposure (0.31 points/month; 95% CI = 0.11-0.51) but not the other groups. There were no significant effects of Exposure Group or Exposure Group × Age for the Bayley-III Cognitive scale. CONCLUSION: Prenatal exposure to cannabis, alone or with tobacco, was not associated with disrupted cognitive or language development during the first three years of life in this sample of high-risk children.