Does Cognitive Improvement in the First Month of Methamphetamine Abstinence Exceed Practice Effects?

Repeated cognitive testing can improve scores even without recovery from drug-related difficulty. A study of early methamphetamine abstinence did not establish significantly greater overall improvement than the change seen in healthy comparison participants.

Why a retested comparison group mattered

Simon and colleagues initially assessed 27 methamphetamine-dependent adults abstinent for four to nine days and 28 healthy comparisons. The battery sampled attention and processing speed, learning and memory, working memory, and executive functions. Eighteen dependent participants maintaining approximately one month of abstinence and 21 comparisons returned for retesting.

An initial difference did not establish a recovery trajectory

At baseline, the dependent group performed worse on a processing-speed test and on the global composite, the latter by approximately 0.31 standard deviations. At retest, the group’s additional overall improvement relative to comparisons was not significant, p = .33. A numerical improvement should not be described as proven recovery.

Practice is an alternative explanation for change

Familiarity with instructions, comfort with testing and learned task strategies can improve later scores. Alternate forms reduce some repetition but do not remove every practice effect. Comparing the change in both groups is consequently more informative than asking whether the dependent group improved from its own starting point.

What the null finding leaves open

Small follow-up samples and attrition limit precision. The study does not prove that recovery cannot occur in a month or that deficits are permanent. Neither was this a methamphetamine-administration trial or an individual fitness-to-drive assessment. Abstinence timing and cognitive scores are different variables from quantitative methamphetamine in a forensic specimen; no blood, urine or oral-fluid impairment cutoff was established.

Related evidence

For a different perspective on interpreting stimulant evidence, see our analysis of Stroop findings across abstinence intervals. Its study population and outcome should remain separate from the present findings.

Primary research

Methamphetamine Dependence and Neuropsychological Functioning: Evaluating Change During Early Abstinence. Original human research. doi:10.15288/jsad.2010.71.335.