Bipolar Disorder: Disease Burden

Epidemiology of Bipolar Disorder

Bipolar disorder is a chronic psychiatric illness characterized by recurrent episodes of mania, hypomania, mixed states, and depression. Various studies have estimated the prevalence of bipolar disorder to be between 1% and 2%. The National Comorbidity Survey suggested a lifetime prevalence of 1.6%.¹ The Epidemiologic Catchment Area (ECA) surveys have suggested a lifetime prevalence of 1.3%.² An epidemiologic study of 38 000 community-dwelling individuals in 10 countries found prevalence rates similar to those reported for the United States.³ However, a recent study suggested a substantially higher prevalence of 3.7% for bipolar spectrum disorders.⁴ Many estimates from community surveys may not include milder forms of bipolar disorder (eg, bipolar II disorder, bipolar disorder not otherwise specified), which could result in underestimation of the true prevalence of the spectrum of the disorder.⁵

Men and women have similar rates of bipolar illness.^3,6 Some evidence suggests that women are more likely to be hospitalized during manic episodes, and that rapid cycling occurs more often in women than in men.^6,7 Women also appear more likely to have predominantly depressive features, rather than manic features over the course of the illness.⁸

Bipolar disorder can occur for the first time at any age. However, the peak period of onset is between the ages of 15 and 19.² A National Depressive and Manic-Depressive Association (NDMDA) survey found that 59% of patients with bipolar disorder experienced their first symptoms during childhood or adolescence.⁸ However, bipolar disorder can also manifest for the first time in later years. One study showed that new onset of mania occurred in 9.3% of a group of patients older than 60 years of age with affective disorders.⁹ Another recent report noted that 6.1% of adults aged 60 and older with bipolar disorder appear to have illness of relatively recent onset.¹⁰

Recurrence rates for bipolar disorder are high even with ongoing therapy. One study found a 73% relapse rate at 5 years, and two thirds of the patients had multiple relapses.¹¹ Other estimates place the relapse rate at about 90%, with nearly half of the relapses occurring within 2 years.¹²

Misdiagnosis and Its Consequences

Misdiagnosis of bipolar disorder is a frequent occurrence and represents a major obstacle to appropriate treatment. In one study, 40% of a group of patients with bipolar disorder had received an incorrect diagnosis of major depression.¹³ Another study found that 25% to 50% of major depression cases were, in fact, bipolar disorder.¹⁴ The NDMDA survey showed that 70% of patients with bipolar disorder were initially misdiagnosed, most often as having major depression. Half of the patients had consulted multiple physicians or other professionals.⁸ On average, 8 years passed before the correct diagnosis of bipolar disorder was made.¹⁵ Reasons for misdiagnosis are manifold, including that patients may not share information regarding manic symptoms with their physicians, depressive symptoms can be easily mistaken for unipolar depressive illness, and, finally, symptoms of bipolar disorder may frequently overlap with those of other psychiatric disorders, including schizophrenia, attention-deficit disorder, and personality disorders.^16,17

Misdiagnosis of bipolar disorder leads to a variety of negative consequences, perhaps the most obvious being a delay in effective therapy. One study found that direct healthcare costs were significantly higher for patients who had delayed use of or did not use mood stabilizers during the first year of treatment for bipolar disorder.¹⁸ Additionally, mood stabilizing therapy may be less effective when initiated after unsuccessful therapy for depressive episodes.¹⁹ In particular, misdiagnosis of bipolar disorder as unipolar depression has substantial clinical implications. Antidepressants have not been shown to be more effective than mood stabilizers in the treatment of acute bipolar depression, and have been shown to be less effective than mood stabilizers in preventing depressive relapse in bipolar disorder.²⁰ Antidepressant therapy can also have a destabilizing effect on the clinical course of bipolar disorder.^21-23 Finally, psychoeducational approaches specific for bipolar illness are supported by evidence-based treatment guidelines,²⁴ and individuals who are misdiagnosed do not receive the benefits of appropriate psychoeducation.

Failure to recognize bipolar disorder has substantial economic consequences. A California study found that patients with unrecognized bipolar disorder have higher rates of hospital use and suicide attempts compared with patients with recognized bipolar disorder.²⁵

Functional Impairment

Bipolar disorder is the sixth leading cause of medical disability worldwide among people 15 to 44 years of age. Bipolar disorder is associated with a greater degree of disability than a number of prominent chronic medical conditions, including osteoarthritis, human immunodeficiency virus infection, diabetes, and asthma.²⁶

Bipolar disorder is associated with high rates of unemployment, job-related difficulties, and interpersonal stress. Two large surveys revealed unemployment rates of about 60%, even among college-educated patients.^27,28 In one of the surveys, 88% of respondents reported occupational difficulties.²⁷ The other survey also showed that 65% of respondents had difficulty maintaining long-term relationships, and 64% had difficult relationships with their children.²⁸

Many patients with bipolar disorder have a poor quality of life, particularly when the condition goes untreated or when comorbid conditions exist. A survey of bipolar patients during euthymia found that their quality of life was similar to or below that of patients with long-term medical conditions.²⁹ A US government study concluded that a woman with bipolar disorder with onset at age 25 loses 9 years of life, 12 years of normal health, and 14 years of effective functioning.³⁰ A 10-year follow-up of patients with bipolar disorder found that about 50% of patients had sustained improvement, whereas 30% to 40% experienced functional decline over time.³¹