Adult ADHD vs. bipolar disorder in the DSM-5 era: a challenging differentiation for clinicians

Patients with adult attention-deficit/ hyperactivity disorder (ADHD) and bipolar disorder can present with similar symptoms, including increased energy, distractibility, disorganization, impulsivity, hyperactivity, and rapid speech. Determining whether the patient has either, or possibly both, of these syndromes can be a complex task. This review attempts to clarify where these disorders overlap, both symptomatically and epidemiologically, and where they diverge, to help clinicians increase the accuracy of their diagnoses. Changes to diagnostic criteria from the fourth to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (from DSM-IV-TR to DSM-5) are discussed, as is the evidence base for pharmacological treatments.

Studies and sources were identified using computerized searches.

Adult ADHD and bipolar disorder have multiple overlapping symptoms, but there are differences in prevalence (ADHD affects 4.4% of adults in the United States versus 1.4% for bipolar disorder), onset of symptoms (usually before age 7 years in ADHD versus after age 12 years in bipolar disorder), disease course (chronic in ADHD versus cyclical in bipolar disorder), mood symptoms (absent in ADHD but always present in bipolar disorder), and psychotic symptoms (absent in ADHD but sometimes present in bipolar disorder). Approximately 20% of adult patients with ADHD also have bipolar disorder, while 10%-20% of patients with bipolar disorder have adult ADHD. Comorbidity of bipolar disorder and ADHD is associated with an earlier age of onset and a more chronic and disabling course of bipolar disorder, as well as more psychiatric comorbidity.

Distinguishing between adult ADHD and bipolar disorder requires careful attention to phenomenology and awareness of epidemiology, with a focus on childhood history, lifetime course of symptoms, and the possibility of comorbidity.