While study strengths include a large and diverse sample, our results should be interpreted in
the context of potential methodological limitations. The cross-sectional design does not
allow us to examine changes in cognitive functioning that may be associated with substance
use and mental health problem severity, and the study lacks information on cognitive
functioning prior to the onset of MA use. Also, the lack of a demographically-matched
control group does not allow us to clearly attribute the findings of cognitive test differences
to MA use or other characteristics. Data on substance use and mental health problems are
self-reported and retrospective, thus may be affected by respondents’ ability to remember
and accurately report information. Future work should longitudinally assess cognitive
functioning in relation to MA use and related factors. Further study of poly-substance use
would be useful in understanding whether differences in cognitive functioning are due to use
of a specific substance or to its interaction with MA and/or other substances.