The purpose of this study is to refine a new assessment tool for Attention Deficit/Hyperactivity Disorder (ADHD) and then to test its validity (i.e. ability to discriminate between individuals with ADHD and healthy controls.

The purpose of this study is to build upon the success the novel approach and software for analyzing electroencephalography (EEG) data to identify biomarkers of ADHD in adults by further refining the method. Then to test the ability of this new assessment tool to differentiate between adults with ADHD and healthy controls by comparing the classification accuracy of the metrics from the new tool to the classification accuracy of existing behavioral tests for ADHD.

Inclusion Criteria:

Specific inclusion criteria for ADHD are:

1. meet established Diagnositic and Statistical Manual-5 criteria for ADHD predominately inattentive or combined subtype with clinically significant levels of impairment, diagnosed by structured clinical interview, the Mini International Neuropsychiatric Interview, and corroborating information
2. Clinical Global Impression-Severity (CGI-S) score ≥ 4 for ADHD
3. no lifetime history of DSM-5 bipolar disorder, psychotic disorder, pervasive developmental disorder, obsessive-compulsive disorder, substance abuse, or substance dependence (except nicotine) as assessed with the Mini International Neuropsychiatric Interview (MINI).
4. able in the opinion of the investigator to complete all required study procedures.

Exclusion Criteria:

Exclusion criteria for both groups are:

1. History of diagnosis of childhood disorder other than ADHD (e.g. autism, dyslexia)
2. history of any general medical condition likely to require chronic use of medication with identified central nervous system (CNS) effects suspected to alter cognitive performance
3. history of seizure disorder, brain tumor, other major neurological disorder or head injury resulting in loss of consciousness
4. serious oxygen deprivation
5. current psychopathology requiring ongoing treatment with antipsychotic medications, mood stabilizers, benzodiazepines, or anticonvulsants
6. current untreated psychopathology which is rated to be primary in terms of severity (greater than ADHD severity)
7. current treatment with guanfacine.

Adults with Attention Deficit Hyperactivity Disorder (ADHD) from local clinics, clinicians, ADHD community resources in the area of each of the three participating Universities (UCLA, UCB, OHSU)