The impact of maternal alcohol and illicit drug use on children’s behavior problems: evidence from the children of the national longitudinal survey of youth
Introduction
In 1996, approximately one out of 10 American children lived in a household where at least one parent met clinical standards for alcohol and/or illicit drug dependence. Larger numbers of children in 1996 lived in households where one or more parents reported any illicit drug use (Huang et al., 1996). Previous researchers, mostly from the fields of psychology and psychiatry, have noted that parental substance abuse is associated with mental health problems in children, but it is unclear whether or not the relationship is causal. The observed positive correlation may be causal if illegal drug or alcohol consumption directly impacts parenting ability and the amount of time parents spend with children, which in turn adversely affect children’s mental health. However, the observed relationship also may be due to unobserved factors that determine both parental substance use and children’s mental health outcomes, such as parental psychiatric disorder, personality, or environment.
The objective of this study is to use a large, national sample of mothers and children to test for evidence of a causal relationship between maternal alcohol, marijuana and cocaine use, and children’s early mental health problems, as measured by an index of behavior problems. Behavior problems during childhood are associated with psychiatric disorders, mental health services use, and delinquency later on in childhood and in adolescence (Gortmaker et al., 1990, Wacschlag et al., 1997). This study is based on the hypothesis that some forms of maternal substance use will interfere with the production of children’s mental health by decreasing the quality of parenting inputs, or by reducing the amount of time mothers invest in producing children’s mental health.
Empirically, establishing a causal relationship between maternal substance use and children’s behavior problems is not straightforward. If unobserved factors exist that are correlated with both maternal substance use and children’s outcomes, an observed positive association may not be causal. For example, if a mother suffers from chronic depression, this psychiatric disorder may lead both to maternal substance use and to children’s behavior problems.
If the relationship between maternal substance use and children’s outcomes can be explained by unobservable factors, programs and policies that reduce maternal substance use will not be effective in improving children’s behavior problems. Alternatively, if maternal substance use is causally linked to children’s outcomes, children will benefit from programs and policies that reduce maternal substance use. This study uses three empirical methods to address this issue: (1) an instrumental variables (IV) method, which uses alcohol and illicit drug prices and policies as identifying instruments; (2) family fixed-effects models, which control for unobserved heterogeneity at the level of the mother’s family of birth; and (3) mother–child fixed-effects models, which control for unobserved heterogeneity at the level of the mother–child pair.
The ordinary least squares (OLS) results of this study suggest that after controlling for a range of socioeconomic and demographic factors, maternal alcohol use, marijuana use and cocaine use are all strong predictors of children’s behavior problems. However, when maternal depression and cigarette use measures are included in the OLS models, alcohol use is no longer a statistically significant predictor of children’s behavior problems. Illicit drug use remains statistically significant. Mother–child and family fixed-effects models are generally consistent with the main OLS findings. The results from IV estimation show no consistent relationship between maternal substance use and children’s behavior problems. The identifying instruments, however, performed very poorly in the first stage, casting doubt on the validity of the IV results. Overall, then, this analysis provides some evidence that the observed association between maternal substance use and children’s behavior problems may be causal.
Section snippets
Previous literature
Researchers have identified a number of physiological, environmental, and genetic pathways that link maternal substance use to children’s behavioral outcomes. First, maternal substance use during pregnancy may affect adversely a developing child’s future behavioral outcomes through teratogenic processes. Second, maternal substance use may disrupt the home environment or affect parenting in a way that leads to children’s behavior problems. Finally, mothers and children may share an unobserved
Theoretical motivation
Theoretically, this study is motivated by the household production and health production frameworks developed by Becker (1965) and Grossman (1972). In our framework, a mother maximizes utility which is a function of the child’s stock of mental health capital and the mother’s stock of relaxation or euphoria capital. Euphoria is produced with a mind-altering substance such as alcohol, marijuana or cocaine, as well as with a time input. The child’s mental health is produced through good parenting
Empirical estimation
The child mental health production function is represented empirically by Eq. (1):and is specific to the ith child of mother j at time t. The output of the production function is measured by the standardized percentile score calculated from the BPI. The variable Ajt represents maternal alcohol and illicit substance use measures. The vectors Xi and Xj include observed, child specific factors and mother-specific factors, respectively, that may impact the
Estimation strategies
This analysis uses three approaches to estimate the coefficient on maternal substance use in Eq. (1). All three methods are intended to adjust for the potential correlation of maternal substance use (Ajt) with uj in the disturbance term. The first method accounts for as much of the unobserved uj as possible in the empirical specification by controlling for observed characteristics of the mother. The second method, IV, purges the maternal substance use measures of their correlation with uj. The
The CoNLSY data
The data used in this study come from the Children of the National Longitudinal Survey of Youth (CoNLSY). The National Longitudinal Survey of Youth (NLSY79) is an annual, national survey that was initiated in 1979 with a sample of 12,686 young people who at that time were aged 14–21. NLSY79 respondents provided extensive information on labor market participation, education, fertility, substance use, attitudes and family background. Beginning in 1986, children of female NLSY79 respondents were
Regression results
Initially, the models are estimated using OLS to establish baseline estimates of the effects of maternal substance use on children’s behavior problems. Although the OLS method ignores the potential endogeneity of maternal substance use, it offers the advantage of being robust to many specification errors. The baseline OLS results are displayed in the first columns of Tables 4 and 5. Next, in an effort to further control for unobserved factors that might affect both maternal substance use and
Summary and conclusions
This study provides some evidence that maternal substance use may be linked causally to children’s behavior problems. Although TSLS results are problematic due to the poor performance of the identifying instruments, OLS models, family fixed-effects models, and mother–child fixed-effects models all suggest that maternal marijuana and cocaine use are associated with increases in 4–15-year-old children’s BPI scores. Maternal alcohol use, as measured by the number of days the mother used alcohol in
Acknowledgements
We would like to express our gratitude to Michael Grossman, Robert Kaestner, Chris Swann, Sherry Glied, David Cutler, Jon Gruber, and two anonymous referees for very helpful comments and insights.
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