Episodic foresight is the ability to visualize oneself experiencing future events. This ability is crucial for planning and fulfilling basic needs. For example, someone without episodic foresight may fail to buy enough food at the grocery store because they are unable to plan ahead for the coming week. A new study investigated whether cannabis users showed disruptive capacity for episodic foresight and whether such a disruption was related to frequency of cannabis use. Participants were Australian adults aged 18 to 25 years who did not have a current or past neurological condition or psychiatric disorder or a history of regular alcohol use. Fifty-seven participants were cannabis users, 23 of whom used cannabis weekly or less, while 34 reported smoking at least three times per week. A control group of non-cannabis users (n = 57) was also utilized. Participants completed testing to assess multiple cognitive functions and were instructed to abstain from substance use 24 hours prior to the tests. Assessments for executive control (mental flexibility, inhibitory control, and cognitive initiation), episodic foresight, and episodic memory were conducted. Tests for the latter two abilities included Autobiographical Interviews (AIs; semi-structured interviews that assess episodic and non-episodic content in the past and future). Participants were instructed to describe a personally-experienced event from the past or future in response to a positive, negative, or neutral cue word. The content from the interviews was transcribed and scored, wherein the number of internal details (episodic details specific to the central event) were the primary measure of episodic future thinking (for future events) and episodic memory (for past events). Data were analyzed using analysis of variance (ANOVA) and effect sizes were quantified using partial eta squared (η2 p). Results indicated there were no group differences on any of the executive functioning measures. Analysis of the AI data indicated there were no significant differences in the number of internal details provided by the control group and recreational cannabis users (p = 0.545); however, regular cannabis users performed significantly worse than the other two groups (p = 0.013 for control group vs. regular users and p = 0.011 for recreational users vs. regular users). The authors interpreted these results to indicate that regular cannabis users exhibited deficits in both episodic foresight and episodic memory.
Take away: This study compared episodic foresight and episodic memory (two important cognitive functions) across adults who abstained from marijuana, used marijuana occasionally, and used marijuana three or more times per week. The latter group performed significantly worse on tests of these abilities than the other two groups.