Joint effects of stress and chronic cannabis use on prospective memory.

RATIONALE: Prospective memory pervades our daily lives and failures can have detrimental consequences. This ability to execute delayed intentions may be impacted by stress, yet few studies have examined these effects. Moreover, as many cannabis users report using cannabis to cope with stress, it is important to understand how stress impacts memory in cannabis users.

OBJECTIVES: We assessed the effects of acute and chronic stress on prospective memory to examine whether stress differentially impacts prospective memory in cannabis users vs. non-users.

METHODS: Forty cannabis users and 42 non-users were assigned an episodic and a habitual prospective memory test before completing either the stress or no stress condition of the Maastricht Acute Stress Test (MAST). Participants were instructed to execute the habitual test during the MAST and the episodic test shortly after the MAST. Chronic stress was measured using the Perceived Stress Scale, and acute stress was measured using subjective ratings and cortisol.

RESULTS: There was a main effect of acute stress indicating that stress detrimentally impacted habitual prospective memory performance. Although there was not a significant stress x cannabis interaction, further planned comparisons indicated the habitual prospective memory impairment was selective to cannabis users. There were also significant negative correlations between (i) episodic prospective memory and both subjective stress as well as chronic stress, and (ii) habitual prospective memory and change in subjective stress.

CONCLUSIONS: This study is the first to reveal detrimental effects of acute stress on prospective memory performance, which may be exacerbated in cannabis users.