When should a child be assessed for ADHD? at what age?

What the evidence says

The American Academy of Pediatrics guideline, widely used by Canadian clinicians as well, recommends starting an ADHD evaluation for any child aged 4 through 18 who is showing academic or behavioral problems along with signs of inattention, hyperactivity, or impulsivity. The Canadian Paediatric Society's own position statements on ADHD were developed after reviewing this same evidence base, including AAP, NICE, and European ADHD guideline groups, and support this general approach for Canadian clinicians. Diagnosing ADHD in children younger than 4 is difficult because normal toddlers change rapidly in attention and activity level, so it's hard to tell typical behavior from a real problem.

It also gets trickier again in the teen years, since the criteria loosen slightly for older adolescents (fewer symptoms are needed, and the deadline for when symptoms must have started shifts from age 7 to age 12). A real evaluation is never a single test. It involves gathering input from parents, teachers, and sometimes the child directly, using standardized rating scales, and ruling out other conditions that can look like ADHD (anxiety, sleep problems, learning disabilities, etc.) before making a diagnosis.

Bottom line for parents: if your child, at any age from about 4 onward, is struggling at school or at home with attention, hyperactivity, or impulsivity, it's reasonable to raise this with your pediatrician or family doctor to start the evaluation process.