Loneliness and executive function in young adults: a temporal dynamics approach

Background The association between loneliness and cognitive decline in older adults is well established, but evidence in young adults remains limited. A key obstacle is measurement. Cognitive function peaks during young adulthood, leaving accuracy near ceiling and reaction times within a narrow range. Under these conditions, conventional summary scores may lack the sensitivity to detect subtle individual differences. This study used a substantially larger sample to re-examine previously reported associations between loneliness and executive function in young adults, and tested whether indices that track how performance changes within a task offer greater sensitivity than traditional summary scores in capturing such differences. Methods Korean undergraduates ( N = 212; M age = 20.57 years, SD = 1.90) completed the UCLA Loneliness Scale and the Depression Anxiety Stress Scales–21, then performed a color–word Stroop task and a computerized Wisconsin Card Sorting Test (WCST). For each task, both a traditional summary score and a temporal dynamics index were computed. Hierarchical regressions tested whether loneliness predicted each outcome after controlling for age, sex, and emotional distress. Results Loneliness did not predict either traditional summary score. In contrast, loneliness predicted a progressive increase in Stroop interference over time ( p < 0.001), with lonelier individuals showing less interference initially but greater interference by the end of the task. Loneliness also predicted greater reaction time (RT) slowing in the WCST, specifically during phases when the sorting rule was still being confirmed relative to phases when it was established ( p = 0.011). Conclusions Loneliness was associated with differences in executive function in young adults, but these differences emerged only as cognitive demands accumulated, not in overall task performance. These results indicate that in young adults, detecting associations between loneliness and executive function may require measures that track performance changes within the task rather than overall averages. Trial registration Not applicable. This study is an observational cross-sectional study of healthy young adults and does not report a health care intervention; therefore, trial registration is not required.