Research and studies first identified ADHD with children. Eventually, research showed other ADHD cases where adults were diagnosed with the disorder. It has also been said that there were adults who were diagnosed with ADHD since their childhood years. Others were diagnosed only during their adulthood stage.

There are a variety of aspects and criteria that one must have and consider before being confirmed to have ADHD. The evaluations and assessments made are done through Conners Rating Scale and Brown Attention Deficit Scale. By this, patients’ inattention and hyperactivity are properly rated and thus may be properly addressed with and treated.

ADHD patients are typically not sensitive or even not aware of the manifested symptoms as well as having the actual disorder. They have the idea and thinking that the symptoms or signs they are experiencing at moment are just results of their lifestyle such as their work career. There are also times when they find it difficult to accept that they have ADHD because of the thought and belief that only children are those who are likely to have this disorder. To those adults that don’t know that they have ADHD, they frequently just feel that it's not possible to do things that involves being systematic or organized. Some of the daily tasks may be considered as a great challenge for some with ADHD. These tasks include waking up early, getting ready for work, and be productive on their job.

There is no exact reason given by studies or research on how and why adults can have ADHD. This disorder has once been considered to be a discipline and or behavior illness which can be a result of a misguided or failure parenting. It has been said also that the other likely causes of ADHD are high level of sugar intake, too much food additives, unnecessary watching of television and other media and family problems. Though they can lead to ADHD, there is still no scientific explanation to give evidence to those factors affecting or causing ADHD.

The majority scientists and even medical experts believe based on research and studies that ADHD is a biological illness due to the malfunction of the nervous system. MRI or Magnetic Resonance Imaging is the tool used to recognize the differences on the brains of individuals affected by ADHD and those living a normal life.

Adult ADHD frequently put forward that the disorder runs with in the bloodline of the family members or known as genetic. Every individual diagnosed with the disorder typically has a relative who is also found to have ADHD. Theories also explained that there are environmental factors as well that can lead to the diagnosis of the disorder as well as birth trauma, brain injuries and any other injuries caused by a serious accident. This is important for us to know these things about adult ADHD.