Problem-solving deficits in methcathinone use disorder.

Rationale: The use of methcathinone (MCAT), a psychostimulant drug that can lead to long-term health risks and executive dysfunction, increased to an alarming rate in recent years. Impairments in low-level executive function have been reported in substance use disorder. However, little empirical evidence is available regarding high-level executive function (e.g., problem solving), which may act as a risk factor for relapse. Objectives: The present study aimed to investigate whether the problem-solving ability was altered in abstinent individuals with methcathinone use disorder (MCUD). Here, we tested fifty male MCUD individuals (short-term MCUD group: twenty-nine patients with MCAT use less than 3 years, long-term MCUD group: twenty-one patients with MCAT use longer than 3 years, which were split by medium years of drug use) and twenty-four well-matched healthy controls (HC) in the Tower of Hanoi task (TOH) to assess the impact of task difficulty on drug-related changes in problem-solving performance. We used several measures to characterize problem-solving performance: the number of mistakes made, the completion time of the task, and the thinking time before the first move. Results: In the low task difficulty condition, the MCUD group and HC group showed similar levels of mistakes and completion time, while in the high task difficulty condition, the MCUD group reported more mistakes (the mean number of mistakes in each trial: 1.41 ± 1.15 vs 0.79 ± 0.76, P = 0.019, Cohen's d = 0.635) and longer completion time in the task (the mean completion time in each trial: 45.83 ± 20.51 s vs 33.40 ± 15.10 s, P = 0.010, Cohen's d = 0.690) than the HC group. The thinking time before the first move did not differ significantly between groups (P = 0.257). We further found that the long-term (more than 3 years) MCUD group made more mistakes than the short-term MCUD group and HC group, mainly in the highly difficult subtasks. The longer time than HCs was reported in the long-term MCUD group among high task difficulty of subtasks. In addition, there was a positive correlation between years of MCAT use and the number of mistakes made in high task difficulty TOH task (r = 0.326, P = 0.021). Conclusions: Chronic methcathinone use was associated with deficits in problem-solving performance, which depended on the degree of task difficulty. The impairment was more evident in the long-term (> 3 years) MCAT group. [ABSTRACT FROM AUTHOR]