Some of the people, some of the time: field evidence for associations and dissociations between stress and drug use

Rationale: Stress's role in drug use is supported by retrospective interview and laboratory studies, but prospective data confirming the association in daily life are sparse. Objectives: This study aims to assess the relationship between drug use and stress in real time with ambulatory monitoring. Methods: For up to 16 weeks, 133 outpatients on opiate agonist treatment used smartphones to report each time they used drugs or felt more stressed than usual. They rated stress-event severity on a 10-point scale and as a hassle, day spoiler, or more than a day spoiler. For analysis, stress reports made within 72 h before a reported use of cocaine or opioid were binned into 24-h periods. Results: Of 52 participants who reported stress events in the 72-h timeframe, 41 reported stress before cocaine use and 26 before opioid use. For cocaine use, the severity of stressors, rated numerically (r _effect=0.42, CL95 0.17-0.62, p=0.00061) and percent rated as "more than a day spoiler" (r _effect=0.34, CL95 0.07-0.56, p=0.0292)], increased linearly across the three days preceding use. The number of stressors did not predict cocaine use, and no measure of stress predicted opioid use. In ecological momentary assessment (EMA) from the whole sample of 133, stress and drug use occurred independently and there was no overall relationship. Conclusions: EMA did not support the idea that stress is a necessary or sufficient trigger for cocaine or heroin use after accounting for the base rates of stress and use. But EMA did show that stressful events can increase in severity in the days preceding cocaine use.