ADHD has three subtypes, which include hyperactive impulsive, primarily inattentive, and combined. With inattentive type, the restlessness is internal. For many with inattentive ADHD, they are the ones daydreaming in class rather than paying attention. However, since they aren’t being disruptive, their symptoms can easily go unnoticed. This is especially true with women and girls, as ADHD is more often diagnosed and treated in males than females, due to differences in how symptoms look.

Difficulties with Diagnosing

One of the challenging aspects of diagnosing an adult is the presence of other comorbidities, some of which can mimic ADHD symptoms. These comorbidities can either be due to a separate disorder or be caused by ADHD.

There’s also an overlap between ADHD and autism spectrum disorder. “About half of people with autism also have ADHD,” Arnold said. With ADHD being more common than ASD, the reverse is not true—with a lower proportion of people with ADHD also having ASD.

Symptoms of developmental disorders such as autism show up the earliest, while ADHD symptoms will show up a little later. Some of the more noticeable symptoms, such as hyperactivity, parents will start noticing early on, while other symptoms, such as inattentiveness, will start becoming more noticeable once children start school.

Advantage of Diagnosis and Treatment

Canu said being diagnosed helps people understand themselves better, which includes gaining perspective on the reasons for some of their struggles. Cognitive behavioral therapy for ADHD, which focuses on managing executive functioning difficulties such as time management, organizational skills, impulse control, and emotional self-regulation. When necessary, medication can also help manage symptoms. For psychologists who do not have prescribing privileges, this can mean working in concert with integrated care teams, primary-care providers, or psychiatrists.

Dealing with Late-life Diagnosis

Receiving a diagnosis as an adult can often bring up some complicated emotions, whether it’s grief over lost opportunities, relief at finally understanding certain struggles, or anger over symptoms having been overlooked for so long. For others, receiving a diagnosis later in life can lead to regrets about lost opportunities, whether it was failing out of school, struggling to establish a career, or experiencing relationship issues because of their ADHD symptoms going overlooked and untreated. Fortunately, receiving a diagnosis later in life could possibly give closure to understand yourself more.


Fairbank, R. (2023). “An ADHD Diagnosis in Adulthood Comes with Challenges and Benefits” Vol. 54. No. 2. Pg. 52. American Psychological Association.