There is no single test or brain scan that can detect ADHD, and the course of treatment will vary depending on the child's problem. The number of tests and interviews the child and parents need to go through before a diagnosis can be made may vary. 

The assessment of ADHD in children and adolescents is often carried out in several stages, where a diagnosis is made based on an overall assessment of the child's symptoms across situations, developmental history, function and other relevant factors. 

The symptoms must have been present across situations before the child is 7 years old, have been persistent for more than 6 months, and have caused significant challenges for the child in everyday life. It must also be assessed whether there are other causes that can better explain the child's symptoms. For example, neglect, substance abuse, depression, anxiety, or sleep difficulties may resemble symptoms of ADHD. Other mental disorders or conditions do not necessarily exclude an ADHD diagnosis, but are important to consider and treat before a definitive ADHD diagnosis is made. 

An assessment is based on a description of symptoms and information from the child, parents and teachers, and any other actors who know the child well. The assessment may include mapping the child's psychosocial, developmental, somatic and psychiatric history and status, as well as the child's strengths and interests. xIn addition, tests and direct observation of the child, such as school observation, are used.

What an investigation might look like

The following elements may be included in the investigation: 

• Conversation with the child or young person
• Anamnesis interview with parents to map developmental history and status
• Mapping the child's symptoms and other concurrent challenges (for example, screening tools and ADHD-RS or SNAP-IV)
• Executive Function Mapping (BRIEF-2)
• Aptitude test (WISC-IV, WISC-V or WAIS-IV)
• School observation or teacher interview 
• Tests that measure the child's attention difficulties, impulsivity, and activity level (e.g. Qb test, TOVA, or CPT)
• Somatic examination by a doctor 

Mapping and findings from the assessment form the basis for further treatment and follow-up needs. Further follow-up should be based on helping the child function better both academically and socially.