How is ADHD diagnosed?

The diagnosis rests on DSM-5-TR criteria applied by a clinician, not on a score

In Canada, ADHD is diagnosed against the criteria in the DSM-5-TR, the American Psychiatric Association's manual, following practice guidelines from CADDRA, the Canadian ADHD Resource Alliance. The criteria describe two symptom lists, nine for inattention and nine for hyperactivity and impulsivity, and then attach conditions that turn a list of traits into a diagnosis.

• Symptom count. At least six symptoms from a list for children, or five for people aged 17 and over, persisting for at least six months.
• Onset. Several symptoms present before age 12.
• Settings. Symptoms present in two or more settings, such as home, work, school or social life.
• Impairment. Clear evidence that the symptoms interfere with functioning, not simply that they exist.
• Exclusion. The symptoms are not better explained by another mental disorder and do not occur only during a psychotic episode.

The clinician then specifies a presentation, predominantly inattentive, predominantly hyperactive-impulsive or combined, and a severity. None of this can be settled by a questionnaire alone, because questionnaires cannot judge onset, impairment or alternative explanations.

The clinical interview is the core of the assessment

Most of the assessment is a structured conversation. The clinician works through each symptom with examples from your life, asks when the difficulties began and what school was like, maps where the problems show up and what they cost you, and takes a developmental, medical, psychiatric and family history. Expect questions about sleep, mood, anxiety, alcohol and substance use, head injuries, medications and major life events, because each can produce or amplify attention problems. Many clinicians use a semi-structured interview such as the DIVA-5, which walks through every DSM criterion for both childhood and adulthood. The kinds of questions asked are listed in what questions are asked during an ADHD assessment?

The interview is also where the clinician forms a view of impairment, which is the part most often missing from self-diagnosis. Two people can report the same symptoms, and one has built a life that absorbs them while the other is losing jobs and relationships. The diagnosis depends on that difference.

Rating scales and information from people who know you support the interview

Standardised questionnaires give the interview structure and a way to compare your answers with population norms. The Adult ADHD Self-Report Scale screens for current symptoms; scales that ask about childhood retrospectively help with the onset question; and functional impairment scales, such as the Weiss Functional Impairment Rating Scale included in CADDRA's toolkit, measure effects on family, work, school, self-care and risk. Where possible the clinician also asks a parent, partner or old friend to complete a scale or answer questions, since ADHD is partly a diagnosis of behaviour others observe, and school reports or report cards serve the same purpose for childhood. The tools in common use are described in what screening tools are used in adult ADHD assessments?

Ruling out other explanations is part of the diagnosis, not an extra step

The exclusion criterion means the assessment spends real time on what else could be going on. Anxiety disorders, depression, bipolar disorder, post-traumatic stress, sleep disorders including sleep apnea, learning disabilities, autism, substance use, thyroid disease, concussion and perimenopause can each produce poor concentration, disorganisation or restlessness, and several commonly coexist with ADHD. The clinician looks at timing, at whether the attention problems come and go with the other condition, and at the childhood history, which is usually the clearest separator. Sometimes a physical examination, blood tests or a sleep study ordered through your family doctor are needed before ADHD can be confirmed or set aside.

Formal psychological testing, meaning cognitive and academic tests administered by a psychologist, is not required to diagnose ADHD in adults and most assessments do not include it. It becomes useful when a learning disability or intellectual question is also on the table, as discussed in do adults need formal psychological testing for ADHD in Canada?

There is no blood test, brain scan or computer test that diagnoses ADHD

Research shows group differences in brain structure, activity and genetics between people with and without ADHD, but none of these translate into a test that can place an individual on one side of the line. Continuous performance tests, which measure attention and impulsivity on a computer task, and quantitative EEG are sometimes offered as objective tests; current Canadian and international guidelines treat them at most as supplementary information, and a normal result does not exclude ADHD. Anyone selling a scan or a game as a stand-alone ADHD diagnosis is overstating what the evidence supports.

Physicians, psychiatrists, nurse practitioners and psychologists can diagnose, and you should leave with a written outcome

In Canada, ADHD can be diagnosed by family physicians, psychiatrists, nurse practitioners and registered psychologists, in person or by video, with the exact mix of professions varying slightly by province. The assessment may be completed in a single long appointment or across two or three shorter ones, depending on the setting and on how much information you bring. At the end the clinician should tell you clearly whether the criteria are met, what presentation and severity apply, what else was considered, and what the recommended next steps are, and should give you a letter or report stating this.

Finding Focus provides online ADHD assessment and treatment for adults and teens in several Canadian provinces. After a short online intake that includes the rating scales, you have one video consultation with a licensed Canadian clinician who applies the DSM-5-TR criteria in the way described here. No referral is needed, assessments start at $399, and the outcome can be that you do not have ADHD, in which case you will be told what the difficulties more likely reflect.