A six-month study linked baseline cognitive performance with later methamphetamine-negative urine results, but its outcome also incorporated missed appointments: missing urine samples were counted as positive. That analytical rule matters when interpreting the paper as evidence about frequency of use.
Karabulut assessed 98 adults with methamphetamine use disorder using card sorting, Stroop and Trail Making tests. Urine toxicology was obtained at baseline and scheduled follow-ups at months one, two, three and six. This was a human observational treatment cohort. Medication choices and adherence were not randomly assigned.
For the follow-up outcome, the number of negative urine results was divided by four scheduled samples. A participant who did not attend and supplied no specimen was assigned a positive result for analysis. That is an imputed outcome, not a laboratory finding of methamphetamine in a specimen that was actually tested. Attendance fell markedly: nine participants, 9.2% of the original cohort, attended at month six.
Several Wisconsin Card Sorting measures were associated with the proportion of negative urines. Other findings weakened after adjustment; for example, the Trail Making B-minus-A association did not remain significant in the adjusted analysis. Regular receipt of prescribed medication was associated with more negative results, but the design cannot separate treatment effects from adherence, attendance and other patient differences.
Intermittent urine testing can miss use between visits. Conversely, treating every missing specimen as positive may classify some abstinent non-attenders as using. The paper itself recognized these limitations. Its outcome therefore combines toxicology observations with assumptions about missing data and cannot precisely count every episode of methamphetamine use. Urine detection also does not establish the degree of functional impairment at a particular time. The study supports further investigation of cognition and treatment engagement, while requiring caution about the stronger claim that baseline tests can reliably forecast an individual’s future use.
See differences between reported use and urine outcomes for a complementary study.