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