To obtain the estimates of the national prevalence of ADHD and ODD of Thai children.

The study was used three-stage stratified sampling to represent most population of each level. 7,118 Thai students graded 1-5 in primary school were recruited in the study and were screened by the SNAP-IV Thai version with the sensitivity 82%. The subjects, whose scores were positive for any subtypes of ADHD or ODD, were interviewed by child and adolescent psychiatrists using DSM-IV criteria. The percentage and 95% Confidence Intervals were used to represent the results.

521 subjects and 200 subjects were diagnosed ADHD and ODD, making a national prevalence of Thai students equals 8.1% (95%CI=7.5-8.7). The prevalencein boy 12% (95%CI=10.9-13.0) was substantially higher than girl 4.2% (95%CI=3.6-4.9), the ratio was 3:1. Considering the difference in regions were found southern region was highest at 11.7% (95%CI=10.0-13.4) and northern region was lowest prevalence equals 5.1% (95%CI=4.0-6.2). The prevalence of ADHD with comorbidity of ODD was 2.1% (95%CI=0.8-2.4). Prevalence of ODD was 3.1% (95%CI=2.7-3.5), which was found highest 5.5% (95%CI=3.7-7.2) in Bangkok.

ADHD prevalence in Thailand is higher, thus an early intervention to prevent the mental health problems and loss of quality population is needed. The health services and education system require changes in attitudes and development of resources. All who care for children including families, schools, communities, health care agencies, the government, and children themselves are required to participate and develop the solution and programs in community.