Lack of longitudinal changes in cognition in individuals with methamphetamine use disorder during the first 6 weeks after commencing treatment.

Background: Methamphetamine use disorder (MUD) associates with cognitive impulsivity deficits. However, few studies have examined longitudinal changes in cognition, and it remains unclear if deficits resolve during early recovery.Objectives: To compare: (1) cognitive function of individuals with MUD at treatment onset and six-weeks later with controls tested over the same period; (2) cognitive changes in MUD-individuals who remained abstinent versus relapsed.Method: We recruited 108 participants meeting DSM-IV-TR criteria for methamphetamine dependence (81 males) and 50 demographically matched controls (38 males); 77 methamphetamine- dependent participants (59 males) and 48 controls (36 males) were retained at follow-up. We administered response inhibition, delay discounting and uncertainty-based decision-making tests at both endpoints. Relapse was defined as methamphetamine concentrations >0.4 ng/mg at follow-up in hair toxicology.Results: We found a significant time-by-group interaction on uncertainty-based decision-making (effect size: η2 = .05), although post-hoc tests to disentangle this interaction yielded inconclusive results (p-range = .14-.40; BF10-range = 0.43-1.67). There were no significant time-by-group interactions on response inhibition or delay discounting, with the former likely a null effect (η2-interaction = .003 and .02; BFincl = 0.23 and 0.71). There were no significant differences in cognitive recovery between individuals who maintained abstinence (n = 12) versus relapsed (n = 65) (η2-range = .003-.04), although evidence was inconclusive toward whether findings reflected true null effects (BFincl-range = 0.33-0.75).Conclusion: We did not find evidence that MUD-related cognitive impulsivity deficits improve beyond practice effects over 6 weeks. Findings do not support previous, albeit conflicting, evidence of early recovery of cognitive deficits in MUD.

Impulsivity predicts poorer improvement in quality of life during early treatment for people with methamphetamine dependence.

BACKGROUND AND AIMS: Methamphetamine dependence is associated with heightened impulsivity and diminished quality of life, but the link between impulsivity and changes in quality of life during treatment has not been examined. We aimed to investigate how different elements of impulsivity predict change in quality of life in the 6 weeks after engaging in treatment. DESIGN: Longitudinal, observational cohort study. SETTING: Public and private detoxification and rehabilitation facilities in metropolitan Melbourne, Australia. PARTICIPANTS: One hundred and eight individuals with methamphetamine dependence (81 male) tested within 3 weeks of commencing treatment; 80 (74%) were followed-up at 6 weeks. MEASUREMENTS: The Continuous Performance Test-2 measured impulsive action (cognitive and motor impulsivity); the Delay Discounting Task measured impulsive choice. Quality of life was measured with the World Health Organization Quality of Life Scale-Brief, which includes social, psychological, physical and environment domains. Control variables included age, gender, estimated IQ, depression severity score, methamphetamine dependence severity score, cannabis dependence severity score and treatment modality. FINDINGS: We found that all three forms of impulsivity were significant predictors of change in the social domain: motor impulsivity (ß = -0.54, P = 0.013), cognitive impulsivity (ß = -0.46, P = 0.029) and impulsive choice (ß = -0.26, P = 0.019). Change in the psychological domain was predicted significantly by motor impulsivity (ß = -0.45, P = 0.046). Control variables of age and depression were associated significantly with changes in the physical domain. CONCLUSIONS: In Australian methamphetamine-dependent individuals, elevated impulsivity predicts lower improvement of social and psychological quality of life in the first 6-9 weeks of treatment.