Early maturation and substance use across adolescence and young adulthood: A longitudinal study of Finnish twins

Abstract

Early maturation, indexed by pubertal development (PD), has been associated with earlier initiation and greater frequency of adolescent substance use, but this relationship may be biased by confounding factors and effects that change across development. Using a population-based Finnish twin sample (N = 3,632 individuals), we conducted twin modeling and multilevel structural equation modeling of the relationship between PD and substance use at ages 12-22. Shared environmental factors contributed to early PD and heavier substance use for females. Biological father absence was associated with early PD for boys but not girls, and did not account for the relationship between PD and substance use. The association between early PD and heavier substance use was partially due to between-family confounds, although early PD appeared to qualitatively alter long-term trajectories for some substances (nicotine), but not others (alcohol). Mediation by peer and parental factors did not explain this relationship within families. However, higher peer substance use and lower parental monitoring were themselves associated with heavier substance use, strengthening the existing evidence for these factors as targets for prevention/intervention efforts. Early maturation was not supported as a robust determinant of alcohol use trajectories in adolescence and young adulthood, but may require longer term follow-up. Subtle effects of early PD on nicotine and illicit drug use trajectories throughout adolescence and adulthood merit further investigation.

Figure 1

Theoretical model of a Cholesky decomposition of variance between pubertal development (PD) and substance use (SU). For ease of presentation, only the additive genetic (A) factors are shown; identical sets of paths for common environmental (C) and unique environmental (E) factors are in the full model, and these sets of paths are correlated between twins within pairs based on the principles of biometrical modeling (see text).

Figure 2

Diagram of the multilevel structural equation model of the relationship between pubertal development (PD), substance use (SU) across adolescence and young adulthood, and hypothesized mediating/confounding factors (peer substance use [Peer] and parental monitoring [Mon]).