A two-year pediatric study did not observe potentially clinically significant deterioration in its key cognitive measures during lisdexamfetamine treatment. Without a control group, the same data could not establish that the medication caused the improvements observed in some tests.
Coghill and colleagues evaluated children and adolescents aged 6–17 receiving optimized lisdexamfetamine in an open-label safety study. All 314 enrolled participants received medication, and 191 completed the study. The CANTAB battery assessed delayed matching, spatial working memory, stopping and reaction time. Cognitive testing was a predefined safety outcome rather than a separate randomized efficacy experiment.
No key variable crossed the study’s predefined deterioration threshold over two years. Improvements meeting the designated threshold occurred in some memory and inhibition measures. That threshold was a prespecified rule for potentially clinically important group change; it should not be confused with proof of an individual clinical benefit or a statistical comparison against untreated development.
Children mature over two years and can improve with repeated testing. Without placebo or an appropriate comparison group, maturation, practice and treatment effects cannot be separated. Attrition also matters: the group completing two years was smaller than the original cohort, and adverse events contributed to discontinuation. The results are reassuring within the tested cognitive domains, but do not establish that no participant experienced any harm or that every cognitive function improved. They do not generalize automatically to methamphetamine use, stimulant misuse or individual impairment at a particular event. Long duration supplies valuable observation; it does not replace a controlled comparison.
See a controlled study distinguishing plasma levels from cognitive outcomes.