The Other Costs of Children: Motherhood, Substance Use, and Depression

There is an extensive theoretical literature identifying the negative effects of the number of children on the outcomes for mothers. While several studies have examined the effects on labor market and health outcomes, little research to date has considered effects on mental health and substance use. I use data from the National Longitudinal Surveys of Youth and a variety of empirical strategies to explore the causal effect of family size on maternal depression and drug use. To address the endogeneity of fertility decisions, I use two natural experiments that exogenously increase the number of children--parity-specific twin births and the gender composition of the first two children. My results provide suggestive evidence that an increase in family size at the third birth parity leads to an increase in a mother's probability of depression. The main findings indicate that a third birth induced by a twin birth or the same-sex composition of the first two children increases a mother's probability of alcohol consumption by about 5.0 percentage points. These estimated effects on alcohol consumption are greater for married mothers. By contrast, I do not find strong evidence of increased marijuana use after the birth of an additional child.