What is the typical age by which symptoms of ADHD must be observed for a diagnosis?

For a diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD), symptoms typically must be present before age 12. This criterion is based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which specifies that in order for ADHD to be diagnosed, the symptoms must be evident in two or more settings (such as home, school, or social situations) and must begin prior to this age.

The rationale behind this age limit is to ensure that the diagnosis captures individuals who manifest signs of the disorder early in their developmental years, allowing for timely intervention. While signs of ADHD may often be noticed earlier, the DSM-5 requires that the symptoms are identifiable and cause impairment in functioning by the age of 12 for a formal diagnosis. This helps differentiate ADHD from other developmental or behavioral issues that can arise later in childhood or adolescence.