Background
Becoming a mother is a developmental transition that has been linked to desistance from substance use. However, timing of motherhood may be a key determinant of cannabis use in women, based on preliminary evidence from teenage mothers. The goal of this study was to identify trajectories of maternal cannabis use, and to determine if maternal age was associated with different trajectories of use.
Methods
This prospective study examined 456 pregnant women recruited at a prenatal clinic, ranging in age from 13-42 years old. The women were interviewed about their cannabis use one year prior to pregnancy and during each trimester of pregnancy, and at 6, 10, 14, and 16 years postpartum.
Results
A growth mixture model of cannabis use reported at each time point clearly delineated 4 groups: non/unlikely to use, decreasing likelihood of use, late desistance, and increasing likelihood/chronic use (Lo-Mendell-Rubin adjusted LRT test statistic = 35.7, p < .001).The youngest mothers were least likely to be in the “non/unlikely to use” group. Younger maternal age also differentiated between late desistance and increasing likelihood/chronic use, versus decreasing likelihood of use post-partum.
Conclusions
This is the first study to demonstrate that younger mothers are more likely to use cannabis across 17 years, including later desistance post-partum and increasing/chronic use. Other substance use and chronic depressive symptoms were also associated with more frequent use. These findings have implications for both prevention and treatment of cannabis use in mothers.