perceptual motor speed and tasks that require mental flexibility.8,9 However, Chang et al.10
found cognitive performance of MA dependent adults who were abstinent for two or more
weeks was in the normal range on standard neuropsychological tests; however, they were
slower on several tasks that required working memory. Some research indicates acute doses
of MA administered to drug-naïve subjects produced improvements in cognitive processing,
while other studies found no cognitive improvements associated with amphetamine
administration.1, 6 Scott et al.11 concluded that the acute cognitive effects of therapeutic
doses of MA tend to increase attentiveness and speed of processing, but also decrease ability
to filter information.
Numerous factors may affect the extent of the impact of MA use on cognition; for example,
younger age at first MA use may be an important factor, as research indicates exposure to
substances in childhood or adolescence produces long-lasting changes in cognition.1 Scott et
al.11 report that the neurocognitive effects of MA may potentially be explained by factors
including demographics (e.g., gender), characteristics such as duration of MA abstinence,
and the influence of common psychiatric and neuro-medical comorbidities such as HIV
infection. The study found that gender had a relatively minor, but significant, influence on
the magnitude of the MA-associated effect sizes, in that a larger proportion of men in a MA
sample was associated with greater overall levels of neuropsychological impairment.
Normal aging is associated with structural and functional changes in prefrontal systems,12
which may lead to additive cognitive deficits in an aging population of MA users.13 Scott et
al.11 report that neither education nor the between-group discrepancy in education had a
significant influence on the effect size estimates, and the length of MA use was also not
correlated with the magnitude of effect.
In addition to demographic characteristics, use of other substances may also affect cognitive
functioning, particularly since many MA users are also extensive poly-drug users, with high
levels of alcohol, marijuana, heroin and other stimulant use commonly reported.14–16
Ornstein et al.17 compared amphetamine users to heroin users on a neuropsychological test
battery and found both groups were impaired on some tests of spatial working memory and
pattern recognition memory, however the heroin users also showed impairment in learning.
Additionally, chronic alcohol abuse has been associated with cognitive impairment
including deficits in learning and memory,18 and research suggests that between 50% and
80% of individuals with alcohol use disorders experience mild to severe neurocognitive
impairment.19
The purpose of this paper is to describe the performance of adults with lengthy MA use
careers on several learning and memory tests in relation to MA use severity, other substance
use characteristics, and mental health problems. A better understanding of demographic and
clinical attributes associated with cognitive problems among MA-users may help identify
individuals in greater need for more intensive or specialized treatment interventions that take
into account possible learning and memory difficulties.