significantly related to poorer accuracy, slower speed and lower efficiency on several
cognitive tests, however, after adjusting for demographic characteristics (specifically age
and education level), findings were not statistically significant. Younger age at first MA use
was related to higher accuracy score on working memory.
DISCUSSION
Overall, this sample of adults with a history of MA use showed somewhat similar accuracy
and efficiency scores on several ANAM tests (spatial and delayed memory) compared to
another sample of substance abuse patients,25 although our sample scored higher on tests of
learning and working memory. Comparing our under 30 subsample to a young adult
normative/reference sample (average age of 23), similar learning (46.4) and working
memory (18.7) efficiency scores were reported,26 suggesting cognitive functioning in our
sample may be somewhat similar to a normative sample. However, substantial variability
was observed based on demographics, substance use, and mental health problems.
Interestingly, our results suggest that for specific memory (delayed and spatial) and learning
tasks, more frequent recent MA use was associated with poorer accuracy but faster cognitive
processing speed. Accordingly, efficiency (throughput) scores showed no association with
recent MA use.
Separate analyses of accuracy and speed scores suggest current/recent MA users may be
able to compensate for lower accuracy with faster cognitive processing, and is suggestive of
conclusions reported by Scott et al.11 that therapeutic doses of MA may increase speed of
processing, but decrease ability to filter information. Similarly, those who were abstinent
from MA for one or more years had higher accuracy scores on learning and spatial memory,
but slower processing speed on the working memory task compared to those who used MA
in the past year. Poorer performance on memory and learning tests was associated with use
of other substances and specific mental health problems. However, lifetime MA use was not
related to cognitive test scores, which is consistent with several studies indicating little or no
relationship of cognitive functioning to cumulative MA quantity and duration of use.27,28
Likewise, age at first MA use was not related to poorer cognitive functioning, in fact,
younger age at first use was associated with higher working memory accuracy.
Regular use of other stimulants (i.e., crack/cocaine) showed a similar effect on accuracy as
recent and past-year MA use, but processing speed scores were somewhat lower for regular
crack/cocaine users compared to those who did not use crack/cocaine regularly, thus,
significantly lower efficiency scores were observed for regular crack users. Previous studies
indicate cocaine users showed significant impairment in short-term verbal and working
memory, and unlike our findings for MA use, neuropsychological test scores were correlated
with lifetime amount of cocaine used.29,30 A lower learning accuracy score was predicted by
regular use of alcohol to intoxication, however, regular use of other substances
(tranquilizers, heroin) was not associated with cognitive test scores.
Some mental health problems found to be prevalent in MA-using individuals (i.e.,
depression, violent/aggressive behavior4) along with age, education and gender were related
to poorer cognitive functioning on various tests in this study. This finding is in contrast with
an earlier study indicating age, gender, and psychiatric problems were of no predictive value
in determining performance on any of the cognitive tasks administered; the sample was 65
MA users with a mean age of 32, all of whom tested positive for MA at the time of cognitive
testing.5 Likewise, in a younger sample of Caucasian, rural, predominantly female MA
users, few cognitive deficits were observed and differences in cognitive performance did not
vary by demographic or clinical characteristics on tests of working memory or learning