Criteria

Inclusion Criteria: Individuals who report drinking ketum decoction more than once a day, daily for the past 12 months.

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Exclusion Criteria: (1) tested positive for illicit drug use including morphine, cannabis, methamphetamine, amphetamine, methadone, benzodiazepine and ketamine; (2) have current or previous history of psychological or neurological problems (self-report); (3) have current or previous alcohol use history (self-report); (4) HIV infections; (5) history of chronic liver disease (e.g. cirrhosis, hepatitis A, B, C, etc.) 6) non-alcoholic fatty liver disease; (7) history of coronary heart disease and diabetes; (8) existing chronic pain condition and (9) history of psychiatric disorders. Exclusion criteria for female particiapns: (1) pregnancy, (2) nursing.

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