Figure 1.
Conceptual model of circadian and sleep pathways to substance abuse. The solid arrows reflect the rich literature supporting bidirectional effects between sleep and substance abuse, and the cumulative human and animal evidence supporting the acute effects of substance use on circadian parameters. The hatched arrows reflect for hypothetical pathways awaiting more research attention, including direct circadian effects on substance abuse, and the reward system-mediated effect of circadian misalignment on substance abuse.