Psychometric evaluation of the PSQI in U.S. college students

Study Objectives: Examine the psychometric properties of the PSQI in two U.S. college samples. Methods: Study I assessed convergent and divergent validity in 866 undergraduates who completed a sleep diary, PSQI, and other sleep and psychosocial measures. Study II assessed PSQI insomnia diagnostic accuracy in a separate sample of 147 healthy undergraduates with and without insomnia. Results: The PSQI global score had only moderate convergent validity with sleep diary sleep efficiency (prospective global measure of sleep continuity; r = 0.53), the Insomnia Severity Index (r = 0.63), and fatigue (r = 0.44). The PSQI global score demonstrated good divergent validity with measures of excessive daytime sleepiness (r = 0.18), circadian preference (r = -0.08), alcohol (r = 0.08) and marijuana (r = 0.05) abuse scales, and poor divergent validity with depression (r = 0.48), anxiety (r = 0.40), and perceived stress (r = 0.33). Examination of other analogous PSQI and sleep diary components showed low to moderate convergent validity: sleep latency (r = 0.70), wake after sleep onset (r = 0.37), sleep duration (r = 0.51), and sleep efficiency (r = -0.32). Diagnostic accuracy of the PSQI to detect insomnia was very high (area under the curve = 0.999). Sensitivity and specificity were maximized at a cutoff of 6. Conclusions: The PSQI demonstrated moderate convergent validity compared to measures of insomnia and fatigue and good divergent validity with measures of daytime sleepiness, circadian phase preference, and alcohol and marijuana use. The PSQI demonstrated considerable overlap with depression, anxiety, and perceived stress. Therefore, caution should be used with interpretation.