ABSTRACT
Chronic pain is prevalent among military veterans and commonly presents with perceived stress and alcohol use. Allostatic load models suggest moderate-severe chronic pain may reflect a state of physiological dysregulation with heightened associations between pain and behavioural health symptoms. Yet little is known about daily associations between pain intensity, perceived stress, and alcohol use in veterans with and without moderate-severe chronic pain. This study examined day-to-day associations between pain intensity, perceived stress, and alcohol use among veterans, and whether associations differ between those with moderate-severe chronic pain and those with less severe pain. A sample of United States military veterans (n = 74) completed smartphone-based daily diary surveys for up to 3 months, providing 4307 days of data. Multi-group dynamic structural equation modelling examined within-person, day-to-day associations between symptoms, among veterans with moderate-severe chronic pain and those with less severe pain. Among veterans with moderate-severe chronic pain, bidirectional positive day-to-day associations emerged between pain intensity and perceived stress (b = 0.06–0.13), and between perceived stress and alcohol use (b = 0.05–0.07). Pain intensity also predicted increased next-day alcohol use (b = 0.04). Perceived stress appeared to act as a mechanism linking alcohol use to subsequent pain intensity (b = 0.01). For veterans with less severe pain, symptom associations differed markedly; higher perceived stress predicted lower next-day pain intensity (b = −0.05). Among veterans with moderate-severe chronic pain, day-to-day associations between pain intensity, perceived stress, and alcohol use appear more entangled. These veterans may experience heightened stress reactivity and poorer coping, requiring tailored interventions to monitor and address day-to-day symptom fluctuations.