Objective: To study the prevalence of substance use and associated factors in school students in Tsunami affected areas in southern Thailand.
Material and Method: The study was a school-based, cross-sectional, anonymous survey that used a translated questionnaire, ESPAD-03, in 5 schools. Chi-square tests and odds ratios were used to evaluate factors associated with substance use.
Results: Two thousand seven hundred and sixteen students (87.8%) were enrolled in the study. Lifetime, last 12 months, and last 30 days prevalence rates of any substance use were 50.3, 33.9, and 24.8%, respectively. Lifetime, last 12 months, and last 30 days prevalence rates of alcohol use were 43.2, 30.1, and 17.5%, respectively. Lifetime and last 30 days prevalence rates of smoking were 21.7 and 12.0%. Fighting, stealing, truancy, running away, unsafe sex, and thought of self-harming were associated with alcohol and substance use. Siblings and friends with alcohol and substance use were risk factors. Close support from parents and friends were protective factors.
Conclusion: There was a high prevalence of smoking, alcohol, and substance use among school students in Tsunami affected areas. Behavioral problems and psychosocial risk factors were associated with history of smoking, alcohol and substance use. School-based intervention in students with behavioral problems seems to be a worthwhile investment. However, longitudinal studies should be done to confirm the correlation of PTSD and substance use.

Keywords: Substance use, Adolescent, Tsunami, Behavioral problem, Risk, Protective factor