The diagnosis of ADHD in adults is on the rise. Applying the ADHD diagnosis, which originally was described in children, to adults has involved a “subjectivization” of some of the diagnostic criteria, i.e., some behavioral features (signs) in children have become experiences (symptoms) in adults. These issues raise the question of how ADHD is best diagnosed in adults? Thus, we examined how ADHD is diagnosed in adults in research.

A review of how ADHD is diagnosed in adults in randomized controlled studies (RCTs).

We include 292 RCTs. We found substantial variation and no consensus about the diagnostic method. More than half of the studies did not seem to include an assessment of general psychopathology, and only in 35% of studies was the ADHD diagnosis allocated by psychiatrists or psychologist. More than half of the studies included patients with psychiatric comorbidity.

These findings raise concerns about the validity of the ADHD diagnosis in many of the included RCTs. It is worrying that securing a reasonably accurate diagnosis is not prioritized in more than half of the studies. If neither clinicians nor researchers can rely on the basic fact the patients in scientific studies diagnostically resemble the patients they are facing, scientific studies risk losing their clinical relevance. Since RCTs can lead to changes in clinical practice, they must be conducted carefully. To advance research on adult ADHD, the quality of the diagnostic assessment must be prioritized, requiring comprehensive differential diagnosis by a skilled psychiatrist or psychologist.