[ADHD prevalence in four Brazilian public schools]

To define the prevalence of attention-deficit/hyperactivity disorder (ADHD) in children from four Brazilian public elementary schools.

Study population consisted of all students from the first through fourth grades, age range 6-12 years, who attended four public elementary schools (CIEPs). This prevalence study comprised two steps. During the first step, school teachers screened their own pupils for ADHD using diagnostic criteria from the Diagnostic and Statistic Manual of Mental Disorders - Fourth Edition (DSM-IV). Screening resulted in two groups of children: suspects and non-suspects. In the second step, parents of suspect children were invited for an interview with the researchers, during which they filled ADHD symptoms questionnaire, and in addition a complete history, pediatric physical exam, and neurological exam were performed. At the end of this step, students were classified as "cases" or "undetermined", i.e., those who partially met ADHD diagnostic criteria.

From a population of 602 students, 461 were recruited. Considering all four elementary schools, ADHD prevalence was 13%. Male to female ratio was 2:1. The most frequent ADHD subtype was the combined one, accounting for 61.7% of all cases.

ADHD prevalence in a sample of school-aged children (13%) was higher than the rate that traditionally has been mentioned (3-5%). Boys were more frequently affected than girls and the most prevalent ADHD subtype was the combined subtype, and the latter two findings are concordant with previous studies.