In one of the primary investigations of the effects of ecstasy use on self-perceived PM deficits, Heffernan, Ling and Scholey (2001a) found increased reports of PM errors in ecstasy users compared to non-users. While these self-reported deficits were consistent across the three PM subscales measured by the PMQ (short-term habitual PM; long-term episodic PM;
internally cued PM), ecstasy users and non-users did not differ significantly in terms of the strategies used to aid PM remembering. Importantly, these group differences were still evident even after controlling for covariates such as other drug use. Although these findings were supported in a second paper (Heffernan, Jarvis, Rodgers, Scholey & Ling, 2001b), more recent research has not been consistent (Montgomery & Fisk, 2007). Montgomery and Fisk (2007) found cannabis use to be a significant predictor of PM errors in ecstasy users on the short-term habitual, long-term episodic and internally cued PM subscales of the PMQ.
However, the increased reports of lifetime cannabis use reported in this study (Montgomery
& Fisk, 2007) compared to previous investigations (Heffernan et al., 2001a; 2001b) may explain the different findings.
The laboratory-based PM data is generally consistent with self-report data in showing clear ecstasy-related impairments in PM. In one of the first investigations to administer a laboratory-based measure of PM to illicit drug users, Rendell et al. (2007) found evidence of PM impairment in both “frequent” and “infrequent” ecstasy users on The “Virtual Week”
task. In stark contrast to cannabis users (McHale and Hunt, 2008), both “frequent” and
“infrequent” ecstasy users displayed deficits in both event- and time-based PM. Nevertheless, event- and time-based PM deficits were attenuated among “infrequent” ecstasy users (Rendell et al., 2007) suggesting that there may be a lifetime dose-related effect of ecstasy use on PM impairment. Interestingly, former users of ecstasy also exhibit event- and time-based impairments in PM on the “Virtual Week” task highlighting the potential long-term deficits resulting from MDMA exposure (Rendell, Mazur & Henry, 2009). Despite these findings, the use of The “Virtual Week” task as an objective PM measure has been criticised on several grounds. Hadjiefthyvoulou and colleagues (2011a) argue that successful performance on The “Virtual Week” task is highly dependent on components of associative learning. For example, prior to the completion of the PM task components, participants must ensure that they are aware of specific responses/behaviours that are paired to different locations on the board. Given that ecstasy users display impairments in paired associative learning (Gallagher et al., 2012; Montgomery et al., 2005), it is possible that poor PM performance observed on The “Virtual Week” task reflects a deficit in associative learning rather than PM itself.
In light of the potential limitations of The “Virtual Week” paradigm, a number of studies have used alternative measures of PM. Zakzanis, Young and Campbell (2003) used the RBMT and found that abstinent ecstasy users made significantly more PM errors than non-users on both event- (Message) and time-based (Appointment) subsets of the measure.
These findings have not been supported by more recent research which has used the RBMT (Hadjiefthvouolou et al., 2011a). Hadjiefthyvoulou and colleagues found that ecstasy users performed similarly to non users on the time-based Appointment and event-based Message subsets of the RBMT but significantly worse than non users on the time-based Belonging subset.
Other event-and time-based measures of PM that were used in Hadjiefthyvoulou et al’s (2011a) investigation included The F1 event-based PM task, The long-term recall PM test and the Karolinska fatigue PM task. In terms of event-based PM performance, ecstasy users exhibited more problems than non-users in remembering to press “F1” during the F1 event-based PM task. Ecstasy/polydrug users were two to three times more likely than non-users to forget to press “F1” on the F1 event-based PM task.
In relation to short-term time-based PM performance, ecstasy/polydrug users had particular difficulty in completing the Karolinska fatigue PM task, especially during the final half of the experiment. Ecstasy/polydrug users only remembered to complete 51% of the fatigue questionnaires that were completed by non-users. With regard to more long-term time-based performance, non-users posted back significantly more delayed recall response sheets than ecstasy users during the 3 week period that followed the initial test-session (long-term delayed recall PM task). Importantly, the evidence from this study is indicative of ecstasy-related impairments on event-based PM tasks as well as short-term and more long-term measures of time-based PM. Findings from this study suggest that ecstasy use induces a globalised deficit in PM. Importantly, the observed group effects remained statistically significant after controlling for several covariates including frequency of cannabis use, total lifetime cannabis use, and current alcohol and tobacco intake. Further analyses of RM and executive functioning (EF) suggested that ecstasy/polydrug-related deficits in PM were not attributable to group differences in these memory processes. These findings increase the likelihood that the PM deficits found among ecstasy/polydrug users can be attributed to the use of ecstasy rather than the use of other illicit drug use or deficits in other aspects of memory.
A further study by Hadjiefthyvoulou and colleagues (2011b) used the sensitive CAMPROMPT measure to investigate differences in PM functioning between ecstasy/polydrug users, cannabis only users and non-illicit drug users. Measures of RM and EF were included to establish whether any observed ecstasy/polydrug-related impairments in PM were attributable to group differences in these processes. Findings showed that ecstasy users performed significantly worse than both cannabis only users and non illicit drug users on event-based subtasks of the CAMPROMPT. Ecstasy users were also significantly impaired on the time-based subtasks on the CAMPROMPT compared to non illicit drug users. Although better RM and EF performance was associated with improved PM
performance, this trend only approached statistical significance and did not underpin the PM impairments that were observed.
While Hadjiefthyvoulou and colleagues (2011a; 2011b) found substantial evidence for a globalised PM deficit among ecstasy/polydrug users, evidence from other studies are inconsistent. Weinborn, Woods, Nulsen and Park (2011) used the Memory for Intention Screening Test and found that ecstasy users were significantly impaired on long-term PM tasks (15-minute delay intervals) compared to high-risk alcohol users and non illicit drug users. This effect was particularly apparent for time-based PM tasks. No group differences were found for short-term PM tasks (2-minute delay intervals). RM and executive functions were not associated with long-term PM performance in ecstasy users confirming findings from previous research (Hadjiefthyvoulou et al., 2011a; 2011b). Long-term PM impairment in ecstasy users was attributed to risky decision making behaviour. From a multiprocess perspective (McDaniel & Einstein, 2000), it is feasible that ecstasy users have particular difficulty in strategic target monitoring over longer delay periods and that this deficit is accentuated in time-based PM tasks. In other words, ecstasy users may be less able to maintain cue-action pairings over longer delay periods compared to non illicit drug users.
The absence of short-term PM deficits in ecstasy users in this study might be explained by the low levels of lifetime ecstasy use. For example, the ecstasy users sampled in Weinborn et al’s (2011) investigation had a relatively low level of lifetime consumption (mean=56.5 tablets) compared to other studies where short-term PM deficits have been found (Hadjiefthyvoulou et al., 2011a, mean=668.90; Hadjiefthyvoulou et al., 2011b, mean=640.90). This is crucial considering that there is an association between lifetime ecstasy use and cognitive performance (Bedi & Redman, 2008).