- Positive toxicology screen for any of the following drugs: cocaine, opiates, methadone, benzodiazepines, barbiturates, amphetamines, methamphetamines, and PCP (Marijuana will be tested for but will not be an exclusionary criterion, participants with valid prescriptions for opiates, benzodiazepines, barbiturates, amphetamines or methadone will not be excluded, participants failing the toxicology screen will be allowed to re‐screen once. These participants will need to be re‐consented before being rescreened to ensure they have received adequate informed consent.)