Remembering to perform an intended task at the appropriate time (prospective memory) is an important aspect of memory functioning in the real world. Previous research has suggested that recreational drug use has a detrimental effect upon this ability. To date relatively few studies have investigated the effect of cannabis use on prospective memory performance. In addressing this hiatus, the present thesis extended this initial research to encompass three aims. Firstly, the thesis evaluated the psychometric properties of an objective prospective memory video procedure in order to mitigate criticisms associated with the use of self-report assessment of memory failures in many of these initial studies. Secondly, the thesis documents a series of quasi-experimental studies comparing cannabis users and non-users in order to examine the effect of cannabis use on prospective memory. Finally, the thesis explored the nature of the deficits observed in an attempt to better understand the neurobiological vulnerability of the cognitive processes underpinning prospective memory to the psychopharmacological effects of cannabis. The findings across all of the studies documented suggested that cannabis use, even in relatively light users with short duration of use, has a detrimental effect on prospective memory in young adults. In addition, the findings presented suggested that the deficits observed in current cannabis users recover on cessation of cannabis use and that time-based prospective memory was more vulnerable to the effects of cannabis use than event-based prospective memory. Furthermore, the findings presented suggested that these deficits arise as a consequence of problems in retrieval of the intentions rather than problems in their encoding and that these retrieval problems arise as a consequence of failures in cue identification rather than problems retrieving the task to be performed. The findings presented found no evidence that the prospective memory deficits observed were related to the number of joints smoked per week, duration of use, estimated lifetime consumption or to the age at which cannabis use commenced. Although the scale of the deficits appeared trivial with cannabis users recalling, on average, only two items fewer than nonusers, the magnitude of the effect was moderate suggesting practical significance, particularly as the deficits were observed in independent cohorts comprising cannabis users with light use and relatively short duration of use.
|Publication status||Accepted/In press - 2011|