Some of these include:

single-photon emission computed tomography (SPECT)
positron emission tomography (PET)
functional magnetic resonance imaging (fMRI)United States medical and mental health professionals follow the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association; the International Classification of Diseases (ICD) published by the World Health Organisation (WHO) is often used by health professionals elsewhere. Until recently ADHD in adults was considered as a continuation of child-onset ADHD. It is now established, however, that also an adult-onset version exists. In a large longitudinal study from 2015 it was found that 28 of the 31 persons who had an ADHD-diagnosis at the age of 38 never had received an ADHD-diagnosis when tested at the ages of 11, 13 and 15. Treatment
As a first step, adults with ADHD should receive psychoeducation about ADHD, so they understand the diagnosis. This is vital to ensure that adults with ADHD can make informed decisions about their treatment, and has other benefits such as improved relationships with others. Treatment often begins with medication selected to address the symptoms of ADHD, along with any comorbid conditions that may be present. Medication alone, while sometimes effective in correcting the physiological symptoms of ADHD, will not address the paucity of skills which many adults will have acquired because of their ADHD (e.g., one might regain ability to focus with medication, but skills such as organizing, prioritizing and effectively communicating have taken others time to cultivate).
For people who cannot be treated with stimulants due to a substance use disorder or other contraindications, atomoxetine is the suggested first line treatment in the UK. In Canada, clinical guidelines suggest that first line treatment be methylphenidate or lisdexamfetamine. Non-stimulant medications are generally second-line treatments in Canada. Non-stimulant medications
The non-stimulant atomoxetine (Strattera), may be an effective treatment for adult ADHD. Although atomoxetine has a half life similar to stimulants it exhibits delayed onset of therapeutic effects similar to antidepressants. Unlike stimulants which are generally controlled substances, atomoxetine lacks addictive potential. It is particularly effective for those with the predominantly inattentive concentration type of attention deficit due to being primarily a norepinephrine reuptake inhibitor. It is often prescribed in adults who cannot tolerate the side effects of amphetamines or methylphenidate. It is also approved for ADHD by the US Food and Drug Administration. A rare but potentially severe side effect includes liver damage and increased suicidal ideation.Viloxazine is a selective norepinephrine reuptake inhibitor that was FDA-approved to treat ADHD in children, adolescents, and adults.Bupropion and desipramine are two antidepressants that have demonstrated some evidence of effectiveness in the management of ADHD particularly when there is comorbid major depression, although antidepressants have lower treatment effect sizes. Psychotherapy
Psychotherapy, including behavioral therapy, can help an adult with ADHD monitor their own behaviour and provide skills for improving organization and efficiency in daily tasks. Research has shown that, alongside medication, psychological interventions in adults can be effective in reducing symptomatic deficiencies.