Impulsivity in amphetamine use disorder: Examination of sex differences

Abstract

Aims: This study aimed to test whether there are sex differences in the relationship between impulsivity and amphetamine use disorder (AMP).

Design: A naturalistic cross-sectional design was used.

Setting: The Tulsa 1000 study was held in Tulsa, OK, USA.

Participants: There were two groups in this study: AMP+ (29F, 20M) and AMP- (57F, 33M).

Measurements: This project focuses on data related to impulsivity: UPPS-P impulsive behavior scale and a stop signal task (SST) during functional magnetic resonance imaging (fMRI) recording. Group, sex and their interaction were compared for UPPS-P ratings and SST fMRI and behavioral responses.

Findings: AMP+ reported higher UPPS-P positive and negative urgency scores (Ps < 0.001; r = 0.56 and 0.51) and displayed greater bilateral insula and amygdala responses across correct SST trials (Ps < 0.001, g range = 0.57-0.81) than AMP-. fMRI results indicated that AMP+ exhibited larger right anterior/middle insula, amygdala and nucleus accumbens signals during successful difficult stop trials than AMP- (Ps < 0.01; g = 0.63, 0.54 and 0.44, respectively). Crucially, two group × sex effects emerged: (a) within females, AMP+ reported larger UPPS-P lack of premeditation scores than AMP- (P < 0.001, r = 0.51), and (b) within males, AMP+ showed greater left middle insula signals than AMP- across correct SST trials (P = 0.01, g = 0.78).

Conclusions: Both female and male amphetamine users appear to be characterized by rash action in the presence of positive and negative mood states as well as heightened recruitment of right hemisphere regions during behavioral inhibition. In contrast, planning ahead may be particularly difficult for female amphetamine users, whereas male amphetamine users may need to recruit additional left hemisphere resources during inhibitory processing.

Keywords: Amphetamine use disorder; behavioral inhibition; functional magnetic resonance imaging; impulsivity; negative urgency; positive urgency; sex differences.

Figure 1.

Selection of participants with and without amphetamine use disorder (AMP+ and AMP−) groups from the Tulsa 1000 sample. CDDR = Customary Drinking and Drug Record. MINI = MINI International Neuropsychiatric Interview. MDD = major depressive disorder. SST = stop signal task.

Figure 2.

UPPS-P Impulsivity results showing that compared to individuals without amphetamine use disorder (AMP−), individuals with amphetamine use disorder (AMP+) reported higher (A) Positive Urgency scores; (B) Negative Urgency scores; and (C) Lack of Premeditation scores, although this group main effect was further qualified by sex: within females, AMP+ had higher scores than AMP−. Asterisks reflect significant differences (p < .001).

Figure 3.

The stop signal task group main effect for correct trials, wherein individuals with amphetamine use disorder (AMP+) exhibited greater bilateral amygdala, left middle insula, and right anterior/middle insula blood oxygen-level-dependent (BOLD) percent signal change from baseline (PSC) than individuals without amphetamine use disorder (AMP−). Error bars reflect ± 1 standard error of the mean. Asterisks reflect significant differences (p < .001).

Figure 4.

The stop signal task group*condition interaction for correct trials. Compared to individuals without amphetamine use disorder (AMP−), those with amphetamine use disorder (AMP+) exhibited higher blood oxygen-level-dependent (BOLD) percent signal change from baseline (PSC) for difficult stop trials within: (A) right anterior insula; (B) right nucleus accumbens; (C) right amygdala; and (D) left posterior insula. AMP+ also showed higher BOLD PSC than AMP− for easy stop trials within right amygdala. Error bars reflect ± 1 standard error of the mean. Asterisks reflect significant differences (p < .01).

Figure 5.

The stop signal task group*sex interaction for correct trials. Males with amphetamine use disorder (AMP+) exhibited greater left middle insula blood oxygen-level-dependent (BOLD) percent signal change from baseline (PSC) than males without amphetamine use disorder (AMP−) but female groups did not differ from each other. Error bars reflect ± 1 standard error of the mean. Asterisks reflect significant differences (p < .05).

Figure 6.

Within individuals with amphetamine use disorder (AMP+), greater summed UPPS-P Positive Urgency and Negative Urgency scores were associated with greater bilateral amygdala blood oxygen-level-dependent (BOLD) percent signal change from baseline (PSC) for correct trials (from the group main effect) during the stop signal task.