A timely warning: Clock drawing errors in young adults and the long-term validity of cognitive screens

Objective: The clock drawing test (CDT) assesses multiple cognitive functions, including visuospatial construction and executive planning, and it is a core feature of many cognitive screens. Recent evidence indicates that young adults may experience difficulties producing an accurate response and we present a closer examination of generational differences in CDT performance in the context of the Montreal Cognitive Assessment (MoCA), where a notable failure rate was observed in our young adult respondents. Method: A total of 165 younger adults (18-35 years) and 53 healthy older adults (65-93 years) completed the MoCA as part of a larger study. CDT performance was scored using MoCA criteria (contour, numbers, hands), and errors were further codified. Contour size was measured to assess constructional differences. Results: About 29.7% of young adults scored below MoCA cutoff (<26), compared to 45.3% of older adults, with only 63.6% of young adults achieving maximum CDT score. Young adults drew significantly smaller clocks, but there were no between-group differences in component scores. Hand placement accounted for the largest proportion of errors. Young adults outperformed older adults on some components of the screen, including executive function, yet still produced equivalent errors on the CDT. Conclusions: Although generally considered robust to demographic factors, the CDT revealed substantial inaccuracies among young adults, likely reflecting reduced familiarity with analogue clocks. These findings reveal the impact that these differences can have on a widely used cognitive screen. Accordingly, they also raise concerns about the long-term validity of the CDT, as expectations may lead to future misclassification in clinical settings.