Early Cannabis Use & Young Adult Sleep Duration: A Biometrically Informed Design

Early cannabis use is linked to cognitive and neuroanatomical outcomes and has become a focus of developmental substance use research. Sleep is an important factor across development that plays a crucial role in the regulation... [ view full abstract ]

Early cannabis use is linked to cognitive and neuroanatomical outcomes and has become a focus of developmental substance use research. Sleep is an important factor across development that plays a crucial role in the regulation of emotions, attention, and numerous other outcomes. Sleep disturbances and substance use may be related through several different mechanisms, but this relationship has rarely been investigated using a genetically informed design. In this study we tested the hypothesis that age of first regular cannabis use is associated with adult sleep duration, and disentangled the genetic and/or environmental influences underlying this relationship in a sample of young adult twins (n=1656). Phenotypically we found that early regular cannabis use was associated with decreased adult sleep duration for both weekdays (β= .16, p=0.000916 and weekends (β= .19, p=0.0000688) controlling for gender, current cannabis use, current alcohol use, and depression. We extended these analyses by performing univariate twin modeling which suggested additive genetic contributions for age of first regular use (a² =51%, p=.0004) and adult weekend sleep duration (a²=20%, 0.04044). Furthermore, we fit  bivariate Cholesky decomposition models to dissect the nature of the association between age of first regular cannabis use and adult sleep duration and found a significant additive genetic overlap between age of first regular cannabis use and weekend sleep (a=.14, p= 0.0020). Lastly, our best fitting model was a directional causal model which yielded a significant path between early cannabis initiation and adult sleep duration on the weekends (β=.11, p =0.0006). Results from these analyses are consistent with a casual model and provide evidence for a novel association between early regular cannabis use and adult sleep duration. These combined results lead us to propose a model where additive genetics play a significant role in the initiation of early cannabis use which in turn affects sleep duration in later life. Findings may have important implications for early substance use and developmental research.

Funding: DA011015, DA042755, DA041120, T32 DA017637 Research Training - Genetics of Substance Abuse.