We expect a bidirectional relationship between pain and mental health: pain negatively affects mental health, while psychological distress amplifies pain perception. In turn, pain and mental health are presumed to directly affect the risk of drug misuse. Yet, drug misuse can also have feedback effects on pain (by increasing pain sensitivity) and mental health (by desensitizing the dopamine system). Although not shown in this conceptual model, sociodemographic characteristics may act as potential confounders. Thus, our models control for sex, age, period, race/ethnicity, marital status, and SES, all of which may have direct effects of pain levels, mental health, and drug misuse.