Methamphetamine (MA) is one of the most commonly abused illicit substances worldwide. Among other problems, abuse of the drug has been associated with reduced cognitive function across several domains. However, much of the literature has not attempted to differentiate cognitive difficulties caused by MA abuse from preexisting cognitive difficulties that are likely caused by other factors. Here, we address this question, evaluating evidence for a priori hypotheses pertaining to six lines of research: (a) animal studies; (b) crosssectional human studies; (c) a twin study; (d) studies of changes in cognition with abstinence from MA; (e) studies of changes in brain structure and function with abstinence from MA; and (f) studies of the relationship between the severity of MA abuse and the extent of cognitive deficits observed. Overall the findings were mixed, with some support for a causal relationship between MA abuse and cognitive decline, and other findings suggesting that there is no relationship. The preponderance of the data, however, does support the possibility that MA abuse causes cognitive decline, of unknown duration, in at least some users of the drug. When averaged across individuals, this decline is likely to be mild in early-to-middle adulthood. However, moderator variables are likely to contribute to the presence and/or severity of cognitive decline exhibited by a given individual.

ABSTRACT. Objective: The purpose of this work was to assess neuropsychological functioning of individuals in early abstinence from methamphetamine dependence and to test for cognitive change over the first month of abstinence. Method: Methamphetamine-dependent subjects in very early abstinence from methamphetamine (4-9 days; n = 27) were compared with healthy comparison subjects (n = 28) on a test battery that evaluated five cognitive domains (attention/processing speed, learning/memory, working memory, timed executive functioning, and untimed executive functioning). A subsample of the methamphetaminedependent subjects (n =18), who maintained abstinence for 1 month, as well as a subsample of the comparison subjects (n = 21), were retested. Results: At the first assessment, the methamphetamine-dependent subjects showed significantly worse performance than the comparison group on a test of processing speed; they also performed 0.31 SDs worse than the control group on a global battery composite score (p < .05). After a month of abstinence, methamphetamine-dependent subjects demonstrated slightly more cognitive improvement than healthy control subjects on the entire cognitive battery, but this difference did not approach statistical significance (p = .33 (Gonzalez et al., 2004(Gonzalez et al., , 2007Hoffman et al., 2006;Kalechstein et al., 2003;Monterosso et al., 2005;Paulus et al., 2003;Salo et al., 2002Salo et al., , 2005Salo et al., , 2007Simon et al., 2000 Simon et al., , 2002Woods et al., 2005). In a meta-analysis of studies comparing individuals with MA abuse or dependence to healthy control subjects (Scott et al., 2007) Despite evidence provided by meta-analytic data, which is collapsed across studies, individual MA-dependent subjects vary in the severity of cognitive deficits they exhibit (Dean and London, 2010), and not all studies of MA-abusing subjects have demonstrated weaknesses. In one study, MA-dependent subjects (n = 44), who were abstinent for a week, did not significantly differ from matched comparison subjects (n = 28) on a battery of motor functioning, verbal memory, attention/processing speed, working memory, reaction time, and executive functioning (Chang et al

Past studies indicate that patients with incentive to fake neuropsychological symptoms are likely to have lower finger tapping scores than credible patients. The present study builds upon past research by investigating finger tapping performance for seven groups: (a) noncredible patients (as determined by failed psychometric and behavioral criteria), and patients with (b) closed head injury, (c) dementia, (d) mental retardation, (e) psychosis, or (f) depression, and (g) healthy older controls. Results showed that men tapped faster than women, requiring that groups be divided by gender. Noncredible male and female patients tapped slower than their comparison group counterparts. Dominant hand score proved to be more sensitive to noncredible performance than other scores (nondominant, sum of both hands, difference between dominant and nondominant), especially for women. Sensitivity, specificity, and positive and negative predictive value tables are presented. With specificity set at 90% for the comparison groups combined, a dominant hand cutoff score of

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BackgroundPrevious studies revealed microstructural abnormalities in prefrontal white matter and corpus callosum of long-term abstinent chronic methamphetamine abusers. In view of the importance of the early abstinence period in treatment retention, we compared 23 methamphetamine-dependent subjects abstinent from methamphetamine for 7–13 days with 18 healthy comparison subjects. As certain metabolic changes in the brain first manifest after early abstinence from methamphetamine, it is also possible that microstructural white-matter abnormalities are not yet present during early abstinence.MethodsUsing diffusion tensor imaging at 1.5 T, fractional anisotropy (FA) was measured in prefrontal white matter at four inferior–superior levels parallel to the anterior commissure–posterior commissure (AC–PC) plane. We also sampled FA in the corpus callosum at the midline and at eight bilateral, fiber-tract sites in other regions implicated in effects of methamphetamine.ResultsThe methamphetamine group exhibited lower FA in right prefrontal white matter above the AC–PC plane (11.9% lower; p = 0.007), in midline genu corpus callosum (3.9%; p = 0.019), in left and right midcaudal superior corona radiata (11.0% in both hemispheres, p’s = 0.020 and 0.016, respectively), and in right perforant fibers (7.3%; p = 0.025). FA in left midcaudal superior corona radiata was correlated with depressive and generalized psychiatric symptoms within the methamphetamine group.ConclusionsThe findings support the idea that methamphetamine abuse produces microstructural abnormalities in white matter underlying and interconnecting prefrontal cortices and hippocampal formation. These effects are already present during the first weeks of abstinence from methamphetamine and are linked to psychiatric symptoms assessed during this period.