Profile of executive and memory function associated with amphetamine and opiate dependence

Abstract

Cognitive function was assessed in chronic drug users on neurocognitive measures of executive and memory function. Current amphetamine users were contrasted with current opiate users, and these two groups were compared with former users of these substances (abstinent for at least one year). Four groups of participants were recruited: amphetamine-dependent individuals, opiate-dependent individuals, former users of amphetamines, and/or opiates and healthy non-drug taking controls. Participants were administered the Tower of London (TOL) planning task and the 3D-IDED attentional set-shifting task to assess executive function, and Paired Associates Learning and Delayed Pattern Recognition Memory tasks to assess visual memory function. The three groups of substance users showed significant impairments on TOL planning, Pattern Recognition Memory and Paired Associates Learning. Current amphetamine users displayed a greater degree of impairment than current opiate users. Consistent with previous research showing that healthy men are performing better on visuo-spatial tests than women, our male controls remembered significantly more paired associates than their female counterparts. This relationship was reversed in drug users. While performance of female drug users was normal, male drug users showed significant impairment compared to both their female counterparts and male controls. There was no difference in performance between current and former drug users. Neither years of drug abuse nor years of drug abstinence were associated with performance. Chronic drug users display pronounced neuropsychological impairment in the domains of executive and memory function. Impairment persists after several years of drug abstinence and may reflect neuropathology in frontal and temporal cortices.

Figure 1

Mean attempts to success per group on 1–6-move planning problems on the one-touch TOL planning task. Planning performance for one-move and two-move problems was not different between the groups. For solving 3–6-move planning problems, all three drug user groups needed significantly more attempts than controls (all p <0.001). Performance did not differ between current and former drug users, but amphetamine users needed significantly more attempts on three-move problems relative to opiate users (p <0.05).

Figure 2

Total errors made to successfully complete the PAL task. All three drug user groups made a significantly greater number of errors compared to controls in learning the correct associations between the patterns and their spatial locations (p = 0.007).

Figure 3

Gender differences regarding how many paired associates (PAL) had been remembered following first presentation. In controls, men remembered significantly more paired associates than women (p = 0.031). In drug users, the performance profile was reversed: women remembered more paired associates than men (p = 0.021). While there was no significant difference between drug using women and female controls, male drug users performed significantly worse than male controls (p<0.001). Note: Neither in the control group nor in the drug user group did male and female participants differ regarding BDI scores, age, or verbal IQ. Male and female drug users did not differ with respect to duration of drug use. *p 0.05