A different depression: clinical distinctions between bipolar and unipolar depression

Abstract

Delayed diagnosis or misdiagnosis can prolong the suffering of patients with bipolar disorder. Accurate early diagnosis is sometimes difficult, however, particularly because patients often present in the depressive phase, which can easily be mistaken for unipolar depression. Unfortunately, therapy appropriate for unipolar depression can increase the risk of manic switch or cycle acceleration in bipolar disorder, especially in those with a family history of bipolarity and suicide, although some antidepressants may be useful in some bipolar patients. In addition, most currently available mood stabilizers, though effective in managing mania, do not effectively resolve depression. In contrast, lamotrigine has shown activity in bipolar depression and has a very low risk of manic switch. Bipolar depression, compared with unipolar depression, is more likely to be associated with hypersomnia, motor retardation, mood lability, early onset, and a family history of bipolar disorder. Awareness of these distinctions can greatly improve diagnosis of bipolar disorder and provide an opportunity for effective therapeutic intervention.

Introduction

Bipolar disorders, which affect between 1.4% and 6.4% of the US population Angst, 1998, Akiskal et al., 2000, Judd and Akiskal, 2003, exact an enormous toll, including increased risk of premature death from suicide. There is growing evidence that bipolar disorder, especially the bipolar II subtype, is underdiagnosed Ghaemi et al., 2000, Benazzi, 1999a, Manning et al., 1997, Dunner and Tay, 1993. Delayed diagnosis or misdiagnosis may lead to delayed treatment, thus prolonging suffering. Unfortunately, accurate and timely diagnosis is sometimes difficult. Patients with bipolar disorder often present in the depressive phase, which can easily be mistaken for unipolar depression. Because the treatment of unipolar depression is substantially different from that of bipolar depression, patients with bipolar depression who are assumed to have unipolar depression will receive inappropriate therapy that can increase the risk of manic switch or cycle acceleration Bowden, 2001, Ghaemi et al., 2000, Altshuler et al., 1995, Wehr et al., 1988. New, validated screening tools, along with an awareness of the importance of a complete history, can greatly improve diagnosis and management. This paper will review the clinical distinctions between bipolar and unipolar depression, and the important differences between bipolar I and II disorder, as well as provide guidance on how the clinician can incorporate more focused diagnostic techniques into a typical office practice. Given the impact of untreated bipolar disorder, the positive influence of increased diligence in diagnosis is substantial.