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. 1989 The British Pharmacological Society