Materials and methods
The present study was a population- based longitudinal study of mental health problems among children who affected by Asian tsunami 2004. Two of three mental health assessments were conducted among adults and children in tsunami affected provinces at 2 and 9 months post-tsunami in February and September 2005 by the collaborative team of The Department of Mental Health (DMH) of the Royal Thai Government and Thailand Ministry of Public Health – US Centers for Disease Control and Prevention Collaboration (TUC). The third assessment was conducted by the DMH in February, 2008, 3 years post-tsunami. The sample size calculation and sampling methods were explained elsewhere17,18. In summary, the sample size was calculated on the basis of estimated prevalence of mental health problems of 5%, with an accuracy of 95% (+/-4%) and design effect of 1.5. For the first assessment, the sample of children aged 7 to 14 years was selected by a multistage cluster household sampling from 10 out of 16 shelters, 16 villages in Phang Nga, and 16 villages in Phuket and Krabi. There were 150 households from Phang Nga and 200 households from Krabi and Phuket were needed. The sample recruited 371 children: 167 displaced in the temporary shelters, 99 not displaced from tsunami affected villages and 105 not displaced from unaffected villages in Phang Nga, Phuket, and Krabi. Because Phang Nga province was serious affected by tsunami. All of affected children (210) in Phang Nga province of the first assessment was aimed to follow-up in the second and the third surveys.