Final answer:
While symptoms of ADHD can appear early, they typically need to be present before age 12 for a diagnosis. Symptoms may not become fully apparent until a child reaches school age, and comorbidity with disorders like depression or OCD is common.
Step-by-step explanation:
It is not entirely accurate to say that behaviors associated with ADHD are typically present before the age of 3. While some symptoms of ADHD can manifest early in life, the diagnostic criteria for ADHD typically require that several inattentive or hyperactive-impulsive symptoms be present before age 12. The full spectrum of ADHD symptoms may not become fully apparent until a child reaches school age, where the demands for sustained attention and impulse control are greater. According to research, ADHD affects approximately three to five percent of children and adults, with a higher prevalence in males than females. The symptoms include inattention, difficulties with executive functioning, impulsivity, and hyperactivity. Importantly, comorbidity is common with ADHD, where individuals may develop secondary disorders such as depression or obsessive-compulsive disorder (OCD).