Abstract
Discrepancies between biological assays and self-report of illicit drug use could undermine epidemiological research findings. Two objectives of the present study are to examine the degree of agreement between self-reported illicit drug use and hair analysis in a community sample of middle-aged men, and to identify factors that may predict discrepancies between self-report and hair testing. Male participants followed since 1972 were interviewed about substance use, and hair samples were analyzed for marijuana, cocaine, opiates, phencyclidine (PCP) and methamphetamine using radioimmunoassay and gas chromatography-mass spectrometry (GC-MS) techniques. Self-report and hair testing generally met good, but not excellent, agreement. Apparent underreporting of recent cocaine use was associated with inpatient hospitalization for the participant's most recent quit attempt, younger age, identifying as African American or other, and not having a diagnosis of antisocial personality disorder. The overestimate of marijuana use relative to hair test was associated with frequent use since 1972 and providing an inadequate hair sample. Additional research is needed to identify factors that differentially affect the validity of both hair drug testing and self-report.