Among all behavioral disorders, ADHD is most commonly diagnosed one & is very common in school age population. Estimates of the prevalence of ADHD in school kids range from 3% - 5% of population. These percentages pertain to kids who get clinical assistance. Studies of community samples in which parents & teachers report symptoms reveal much higher percentage.
In both children & adolescents, ADHD has traditionally been more common in boys than in girls. The ration is 4:1 in general population survey & 9:1 in clinical studies. The difference in results between 2 studies suggests a bias in referral - girls with the disorder are less likely to be referred for treatment than boys. This may be because boys with ADHD are more likely to show aggressive -impulsive behavior, whereas girls with this disorder are more likely to be primarily inattentive.
Another sex difference is the change in the number if individuals who meet the diagnosis in different ages. Adjacent diagram shows that the rate of affected girls decreases slightly from age 10 to age 20 whereas the rate of affected boys exhibits a sharp drop over the same period. Because girls tend to display more attentional problems than disruptive behavior.
Frequent diagnosis of ADHD among schoolchildren has raised concern among parents. What is normal childhood behavior? What's the normal threshold that separates normal behavior from classified disorder? These are important questions because diagnosis brings several consequences. Positive effect is that the child's behavior may then be treated. Negative effect is that the child may receive a label that may bring disadvantages, may be in later life. Further, the label may be incorrect if it's basis is only school report.
Many kids show inattention, hyperactivity, impulsivity, mood swing etc collectively or separately at different stages of school life. So, the diagnosis of this disorder has every opportunity to become biased or judgmental. ADHD diagnosis is largely subjective & depends on who is asked & which criterias are used! Without some agreement on standards for meeting DSM criteria, there will continue to be wide variation in estimation.