Abstract
BackgroundLong-term amphetamine and methamphetamine dependence has been linked to cerebral blood perfusion, metabolic, and white matter abnormalities. Several studies have linked methamphetamine abuse to cortical grey matter reduction, though with divergent findings. Few publications investigate unmethylated amphetamine's potential effects on cortical grey matter. This work investigated if amphetamine dependent patients showed reduced cortical grey matter thickness. Subjects were 40 amphetamine dependent subjects and 40 healthy controls. While all subjects were recruited to be free of alcohol dependence, structured clinical interviews revealed significant patterns of alcohol use in the patients. Structural magnetic resonance brain images were obtained from the subjects using a 1.5 Tesla GE Signa machine. Brain cortical thickness was measured with submillimeter precision at multiple finely spaced cortical locations using semi-automated post-processing (FreeSurfer). Contrast analysis of a general linear model was used to test for differences between the two groups at each cortical location. In addition to contrasting patients with controls, a number of analyses sought to identify possible confounding effects from alcohol.ResultsNo significant cortical thickness differences were observed between the full patient group and controls, nor between non-drinking patients and controls. Patients with a history of co-morbid heavy alcohol use (n = 29) showed reductions in the superior-frontal right hemisphere and pre-central left hemisphere when compared to healthy controls (n = 40).ConclusionsAmphetamine usage was associated with reduced cortical thickness only in patients co-morbid for heavy alcohol use. Since cortical thickness is but one measure of brain structure and does not capture brain function, further studies of brain structure and function in amphetamine dependence are warranted.
Highlights
Long-term amphetamine and methamphetamine dependence has been linked to cerebral blood perfusion, metabolic, and white matter abnormalities
At a reviewer's suggestion, contrast c was run with the original subject group (A>1, n = 29) but with years of heavy alcohol use added to the model as a covariate
The results of each of the contrast analyses were as follows: a) All amphetamine users compared to healthy control subjects (A0-1 + A>1 vs. control) showed no significant differences for any cortical region. b) Patients with limited heavy alcohol use compared to healthy controls (A0-1 vs. control) showed no significant differences for any cortical region. c) Patients with more than 1 year of heavy alcohol use compared to healthy controls (A>1 vs. control) showed thinner cortex in right hemisphere superior-frontal regions and left hemisphere pre-central regions in comparison to healthy controls
Summary
Long-term amphetamine and methamphetamine dependence has been linked to cerebral blood perfusion, metabolic, and white matter abnormalities. Several studies have linked methamphetamine abuse to cortical grey matter reduction, though with divergent findings. Few publications investigate unmethylated amphetamine's potential effects on cortical grey matter. This work investigated if amphetamine dependent patients showed reduced cortical grey matter thickness. They are among the most commonly abused illicit drugs after cannabis [1]. The combination of perfusion, metabolic, and white matter abnormalities provide biological mechanisms. The lower fractional anisotropy noted by [14] was interpreted as evidence for axonal injury It has been observed in Alzheimers patients that blood perfusion abnormalities are evident before cortical loss [15]. The Hawaii Aging with HIV cohort study has provided evidence linking WMHs with cortical atrophy [16]
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