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Disrupted 'reflection' impulsivity in cannabis users but not current or former ecstasy users.

Clark L, Roiser JP, Robbins TW, Sahakian BJ - J. Psychopharmacol. (Oxford) (2008)

Bottom Line: However, current findings are inconsistent.Despite elevated scores on the Impulsivity subscale of the Eysenck Impulsiveness-Venturesomeness-Empathy questionnaire, the current and previous ecstasy users did not differ significantly from the drug-naive controls on the Information Sampling Test.However, the lack of effects in the two ecstasy groups suggests that the relationship between serotonin function, ecstasy use and impulsivity is more complex.

View Article: PubMed Central - PubMed

Affiliation: Behavioural and Clinical Neuroscience Institute, Department of Experimental Psychology, School of Clinical Medicine, University of Cambridge, and Addenbrooke's Hospital, Cambridge, UK. lc260@cam.ac.uk

ABSTRACT
Evidence for serotonin involvement in impulsivity has generated interest in the measurement of impulsivity in regular ecstasy users, who are thought to display serotonergic dysfunction. However, current findings are inconsistent. Here, we used a recently developed Information Sampling Test to measure 'reflection' impulsivity in 46 current ecstasy users, 14 subjects who used ecstasy in the past, 15 current cannabis users and 19 drug-naïve controls. Despite elevated scores on the Impulsivity subscale of the Eysenck Impulsiveness-Venturesomeness-Empathy questionnaire, the current and previous ecstasy users did not differ significantly from the drug-naive controls on the Information Sampling Test. In contrast, the cannabis users sampled significantly less information on the task, and tolerated a lower level of certainty in their decision-making, in comparison to the drug-naive controls. The effect in cannabis users extends our earlier observations in amphetamine- and opiate-dependent individuals (Clark, et al., 2006, Biological Psychiatry 60: 515-522), and suggests that reduced reflection may be a common cognitive style across regular users of a variety of substances. However, the lack of effects in the two ecstasy groups suggests that the relationship between serotonin function, ecstasy use and impulsivity is more complex.

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Related in: MedlinePlus

Performance on the Information Sampling Test in the Current and                            Ex-ecstasy users, cannabis users and drug-naïve controls, in                            terms of the probability of making a correct response at the time of                            decision [P(Correct)]. These data are collapsed across                            the two conditions of the task (Fixed Reward and Reward Conflict) given                            the absence of a significant group × condition interaction                            term. Error bars display standard error of the mean. The asterisk                            signifies P < 0.05 in the                            comparison against drug-naïve controls.
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Figure 1: Performance on the Information Sampling Test in the Current and Ex-ecstasy users, cannabis users and drug-naïve controls, in terms of the probability of making a correct response at the time of decision [P(Correct)]. These data are collapsed across the two conditions of the task (Fixed Reward and Reward Conflict) given the absence of a significant group × condition interaction term. Error bars display standard error of the mean. The asterisk signifies P < 0.05 in the comparison against drug-naïve controls.

Mentions: A mixed-model ANOVA of P(Correct) data (the probability of being correct at the point of decision), with Condition (Fixed Reward, Reward Conflict) as a within-subjects variable and Group and Gender as between-subjects variables, revealed a significant main effect of Condition (F1,86 = 95.8, P < 0.0001). As expected, subjects tolerated more uncertainty [a lower P(Correct)] in the Reward Conflict condition than the Fixed Reward condition, thus demonstrating sensitivity to the task contingencies (see Table 3). There was a significant main effect of Group (F3,86 = 5.45, P = 0.002), and a significant Group × Gender interaction (F3,86 = 4.53, P = 0.005). The other terms did not attain significance (all F < 1), and notably, the Group × Condition interaction was not significant (F3,86 = 0.621, P = 0.603) suggesting comparable sensitivity to the change in conditions across groups. Post hoc group comparisons (Tukey’s) collapsed across Condition showed that the cannabis users opened significantly fewer boxes compared with the Ex-ecstasy group (P = 0.013), and differed at trend from the Current ecstasy users (P = 0.076) and the drug-naïve controls (P = 0.078). There were no differences between the ecstasy groups and drug-naïve controls (see Figure 1). An a priori planned contrast confirmed a significant difference between the cannabis users and the drug-naive controls (t32 = 2.31, P = 0.027) with a large effect size (Cohen’s d = 0.81).


Disrupted 'reflection' impulsivity in cannabis users but not current or former ecstasy users.

Clark L, Roiser JP, Robbins TW, Sahakian BJ - J. Psychopharmacol. (Oxford) (2008)

Performance on the Information Sampling Test in the Current and                            Ex-ecstasy users, cannabis users and drug-naïve controls, in                            terms of the probability of making a correct response at the time of                            decision [P(Correct)]. These data are collapsed across                            the two conditions of the task (Fixed Reward and Reward Conflict) given                            the absence of a significant group × condition interaction                            term. Error bars display standard error of the mean. The asterisk                            signifies P < 0.05 in the                            comparison against drug-naïve controls.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2637477&req=5

Figure 1: Performance on the Information Sampling Test in the Current and Ex-ecstasy users, cannabis users and drug-naïve controls, in terms of the probability of making a correct response at the time of decision [P(Correct)]. These data are collapsed across the two conditions of the task (Fixed Reward and Reward Conflict) given the absence of a significant group × condition interaction term. Error bars display standard error of the mean. The asterisk signifies P < 0.05 in the comparison against drug-naïve controls.
Mentions: A mixed-model ANOVA of P(Correct) data (the probability of being correct at the point of decision), with Condition (Fixed Reward, Reward Conflict) as a within-subjects variable and Group and Gender as between-subjects variables, revealed a significant main effect of Condition (F1,86 = 95.8, P < 0.0001). As expected, subjects tolerated more uncertainty [a lower P(Correct)] in the Reward Conflict condition than the Fixed Reward condition, thus demonstrating sensitivity to the task contingencies (see Table 3). There was a significant main effect of Group (F3,86 = 5.45, P = 0.002), and a significant Group × Gender interaction (F3,86 = 4.53, P = 0.005). The other terms did not attain significance (all F < 1), and notably, the Group × Condition interaction was not significant (F3,86 = 0.621, P = 0.603) suggesting comparable sensitivity to the change in conditions across groups. Post hoc group comparisons (Tukey’s) collapsed across Condition showed that the cannabis users opened significantly fewer boxes compared with the Ex-ecstasy group (P = 0.013), and differed at trend from the Current ecstasy users (P = 0.076) and the drug-naïve controls (P = 0.078). There were no differences between the ecstasy groups and drug-naïve controls (see Figure 1). An a priori planned contrast confirmed a significant difference between the cannabis users and the drug-naive controls (t32 = 2.31, P = 0.027) with a large effect size (Cohen’s d = 0.81).

Bottom Line: However, current findings are inconsistent.Despite elevated scores on the Impulsivity subscale of the Eysenck Impulsiveness-Venturesomeness-Empathy questionnaire, the current and previous ecstasy users did not differ significantly from the drug-naive controls on the Information Sampling Test.However, the lack of effects in the two ecstasy groups suggests that the relationship between serotonin function, ecstasy use and impulsivity is more complex.

View Article: PubMed Central - PubMed

Affiliation: Behavioural and Clinical Neuroscience Institute, Department of Experimental Psychology, School of Clinical Medicine, University of Cambridge, and Addenbrooke's Hospital, Cambridge, UK. lc260@cam.ac.uk

ABSTRACT
Evidence for serotonin involvement in impulsivity has generated interest in the measurement of impulsivity in regular ecstasy users, who are thought to display serotonergic dysfunction. However, current findings are inconsistent. Here, we used a recently developed Information Sampling Test to measure 'reflection' impulsivity in 46 current ecstasy users, 14 subjects who used ecstasy in the past, 15 current cannabis users and 19 drug-naïve controls. Despite elevated scores on the Impulsivity subscale of the Eysenck Impulsiveness-Venturesomeness-Empathy questionnaire, the current and previous ecstasy users did not differ significantly from the drug-naive controls on the Information Sampling Test. In contrast, the cannabis users sampled significantly less information on the task, and tolerated a lower level of certainty in their decision-making, in comparison to the drug-naive controls. The effect in cannabis users extends our earlier observations in amphetamine- and opiate-dependent individuals (Clark, et al., 2006, Biological Psychiatry 60: 515-522), and suggests that reduced reflection may be a common cognitive style across regular users of a variety of substances. However, the lack of effects in the two ecstasy groups suggests that the relationship between serotonin function, ecstasy use and impulsivity is more complex.

Show MeSH
Related in: MedlinePlus