How Do Cannabis Users Mentally Travel in Time: Evidence from an fMRI Study of Episodic Future Thinking

Background: Episodic Future Thinking (EFT) is a cognitive function that allows individuals to imagine novel experiences that may happen in the future. Prior studies show that EFT is impaired in different groups of substance users, such as alcohol and heroin users. However, there is no evidence regarding the neurobiological mechanisms of EFT in cannabis users.Aim: We aimed to compare brain activations of regular cannabis users and non-using controls during an EFT fMRI task. Exploratory analyses were also conducted to investigate the association between EFT and cannabis use variables (e.g., duration of use, age-onset, etc.).Method: Twenty current cannabis-users and 22 non-users underwent a single session fMRI while completing a task involving envisioning future-related events and retrieval of past memories as a control condition. The EFT fMRI task was adapted from the autobiographical interview and composed of 20 auditory cue sentences (10 cues for past and 10 cues for future events). Participants were asked to recall a past or generate a future event, in response to the cues, and then rated their vividness after each response. Results: We found that cannabis-users compared to non-user controls had lower activation within the cerebellum, medial, and superior temporal gyrus, lateral occipital cortex, and occipital fusiform gyrus while envisioning future events. Cannabis-users rated the vividness of past events significantly lower than non-users (P<0.005). There were no significant group differences for rating the vividness of future events (P=0.052). Conclusion: Cannabis users, compared to drug-naïve controls, have lower brain activation in EFT relevant regions. Thus, any attempts to improve aberrant EFT performance in cannabis-users may benefit from EFT training.