Craving mediates the association between affect and substance use in daily life among individuals with substance use disorders.

Background: Craving, the desire to use substances, is a key diagnostic feature for substance use disorders (SUDs) that predicts substance use. Experiencing affective states, both positive (PA) and negative affect (NA), are also implicated in SUDs. Yet, their dynamic interrelationships with craving and substance use remain unclear, particularly at the within-person level of analysis. This study aimed to use ecological momentary assessment (EMA) in daily life to test whether craving mediates the association between PA/NA and subsequent substance use. Methods: Adults with SUDs (N = 36), from outpatient addiction treatment centers, were included in an observational study using EMA over 14 days prior to randomization in a clinical trial. They completed EMA surveys three times daily [midday, afternoon, evening], reporting on PA, NA, craving, and substance use. Multilevel mediation models with bootstrapping were used to examine whether craving mediated within-person associations between affect (PA and NA) and subsequent substance use. Results: Craving significantly mediated the association between affect and subsequent substance use. Higher PA was associated with lower craving at the same timepoint, which in turn led to reduced likelihood of substance use at the next timepoint (β=-0.04, p = 0.02). Conversely, higher NA was associated with higher craving, leading to greater likelihood of substance use at the next timepoint (β=0.08, p = 0.03). Conclusion: At the within-person level, craving mediates the association between affective states and subsequent substance use in individuals with SUD. Targeting momentary affect and craving in daily life, such as through ecological momentary interventions, is a promising strategy for treating SUDs.