Parental Effects on Obesity, Smoking, and Drinking in Children and Adolescents: A Twin Study

Parenting style has been associated with children's weight-related outcomes and health behaviors, but this relationship may be confounded by genetic influences. Using a twin design to better control for genetics and shared home environments, this study aimed to estimate the longitudinal parental effects on obesity, smoking, and drinking in children and adolescents.

Data were retrieved from the first two waves of the German Twin Family Panel. A total of 631 pairs of same-sex monozygotic twins were analyzed, including three birth cohorts aged 5, 11, and 17 years. Self-reported parenting styles were measured in five dimensions: emotional warmth, psychological control, negative communication, monitoring, and inconsistent parenting. Outcome variables included children's body mass index z-score (BMIz) and smoking and alcohol drinking frequency. The differencing method was used to examine the relationship between within-monozygotic pair differences in parenting styles and health outcomes, controlling for differences at baseline, genetic influences, and other shared characteristics between twins.

Controlling for genetics, shared environmental effects, and body weight status at baseline, the twin who received harsher parenting in communication had lower BMI than their cotwin. Subgroup analyses found that negative communication had a stronger impact on the youngest cohort and female twins. Paternal parenting differentially relates to child weight compared to maternal parenting. No concurrent and long-lasting effects of paternal parenting on smoking and drinking were found.

The twin study design is a unique epidemiological tool to measure the contribution of genetics as opposed to the environment, to a given health trait. This study found that negative communication was associated with lower BMI in German twin families. However, it failed to identify strong evidence for the causal link between other parenting dimensions and child's weight status and alcohol and tobacco use. More twin studies with objective measurements are warranted to understand the critical role of parenting, especially family communication, in predicting children's BMIs and their health behaviors across cultures.