Self-report reliability and symptomatology of habitual caffeine consumption.

1. A large body of research on the demography of caffeine use and its potential health consequences has been undermined by the absence of empirical data on the reliability of retrospective self-reports of caffeine consumption. 2. The principal aim of the present study was to use standard bioanalytic method to assess the reliability of subjects' self-reported caffeine use. Saliva samples were obtained from 142 first-and second-year medical students and assayed for caffeine and paraxanthine. 3. Self-reported caffeine use was found to be significantly correlated with salivary caffeine (r = 0.31, P less than 0.001) and paraxanthine (r = 0.42, P less than 0.001), thereby providing qualified support for use of questionnaires to estimate patterns of caffeine consumption. 4. A secondary aim of the study was to extend previous research concerning the symptomatology of caffeine use by examining the association between caffeine exposure and a variety of measures of somatic and psychological health. Caffeine consumption was reliably associated with the self-reported occurrence of somatic symptoms, but not psychological well-being.