Adult ADHD is often comorbid with psychiatric disorders: depressive or bipolar disorders, anxiety disorders, other destructive disorders, or nicotine dependency. Although the pathological backgrounds of these comorbidities are diverse, some of them, except bipolar disorder, are partly secondary to difficulties associated with ADHD. Many adults with ADHD visit psychiatrists with psychiatric symptoms. Focusing on the growth history and difficulties in daily life persisting after the remission of mood or anxiety disorders enables psychiatrists to diagnose adult ADHD. However, the diagnosis of adult ADHD is sometimes difficult, because ADHD symptoms can be regarded as symptoms of psychiatric disorders. There exist, however, slight differences in symptoms of adult ADHD and psychiatric disorders. There is some evidence on psychopharmacological interventions. In adult ADHD comorbid with bipolar disorders, it is important to stabilize mood change before treating ADHD symptoms. On the other hand, in adult ADHD comorbid with depressive disorders, it is acceptable to treat depressive and ADHD symptoms at the same time. In adult ADHD with anxiety disorders, atomoxetine can reduce anxiety as well as ADHD symptoms. In the diagnosis and treatment of adults, it is essential to assess their history from childhood to adulthood, and examine and intervene multi- dimensionally, including from the viewpoint of psychosocial aspects.
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