As there is no single test to diagnose ADHD, it is necessary to have a comprehensive evaluation. This will allow a diagnosis to be established, as well as being able to eliminate other causes. It will also highlight if co-existing conditions are present or not. The evaluation requires time and effort. It should include an extensive history and clinical assessment of the individual’s social, academic, emotional functioning, and developmental level.

Although there are various professionals that can diagnose ADHD, it is best conducted by professionals who specialise in treating ADHD patients. These include psychiatrists, clinical psychologists, and paediatricians.

It is a complex process to determine whether a child has ADHD. Similar symptoms such as anxiety, depression and some learning disabilities, can be mistaken for ADHD. In some cases, the other symptoms could be the primary diagnosis. In yet other cases, the symptoms may co-exist with the ADHD. It is so important to do a complete and thorough history from parents and teachers, and the child, if appropriate. There are checklists that help to eliminate other disorders. The checklists also factor in behaviours appropriate to age, and show when symptoms are extreme for the child’s developmental level.

For adults, diagnosis involves collecting information from various sources. This can include ADHD symptom checklists, rating scales for standardised behaviour, a detailed history of past and current functioning, and information obtained from family members or significant others who know the person well. ADHD cannot be diagnosed properly from brief office observations or just by talking to the person. The individual might not always exhibit the symptoms of ADHD in the office, and the diagnostician needs to take a thorough history of the individual’s life. A diagnosis of ADHD must include consideration that co-occurring conditions might be present.

As part of the evaluation, a physician should conduct a thorough examination. It should include an assessment of hearing and vision to rule out other medical problems that may be causing similar symptoms to ADHD. In rare cases, people with ADHD may also have a thyroid dysfunction. Diagnosing ADHD in an adult requires an evaluation of their childhood history including any problems in behaviour and academic domains, as well as examination of current symptoms and coping strategies.