A retrospective study found a curved association between longer methamphetamine abstinence and better cognitive scores in people with HIV. Age did not significantly modify the global association, although one processing-speed relationship differed by age.
The analysis used data from 122 people with HIV and a lifetime methamphetamine use disorder. Researchers compared linear, piecewise and curvilinear models relating reported abstinence duration to demographically adjusted neuropsychological scores. They then examined age-group interactions for global and domain-specific performance. This was an observational analysis rather than random assignment to an abstinence period.
A log-transformed abstinence model fit best, with stronger positive associations at shorter durations and a flatter slope later. Age group did not moderate global scores. At the domain level, information-processing speed showed moderation, with the steepest association in the youngest group. That specific interaction should not be expanded into a claim that younger age governed recovery across all abilities.
The fitted curve describes differences in the available retrospective data; it is not a directly observed recovery curve for every participant. HIV-related factors, exposure histories, other conditions and selection can contribute to performance. The sample was overwhelmingly male, further limiting generalization. A population association also cannot specify when a particular person regained capacity for work or driving. The study supports testing non-linear relationships and domain-specific age effects, while requiring caution about causal language and individual timelines. Longer abstinence and higher scores occurring together do not prove that abstinence alone caused the entire difference.
See a study measuring cognitive change over a year.