BPAD are chronic disorders with a high rate of recurrence and relapses. More than 90% of individuals who have a single manic episode will have future episodes (Hopkins and Gelenberg, 1994). Ten to 15% of patients will have more than 10 episodes in their life. Bipolar disorder is therefore one of the leading causes of disability which contributes to the important economic burden of bipolar disorder to society. Patients with BD suffer great losses in productivity, with more bed rest and absenteeism days (see Pini et al., 2005 for review). The economic burden was estimated in a cost-to-illness study around US$45 billion in 1991 in the USA, representing 70% of the annual cost of schizophrenia (Wyatt and Henter, 1995). Worldwide, bipolar disorder is listed as the sixth leading cause of disability (Murray and Lopez, 1996).
The lifetime prevalence of BPAD, based on the DSM-IV criteria, is ranging from 1,3% to 1,6% with a sex-ratio around 1 (Weissman et al., 1996). The peak age of onset seems to fall around 20 yo in Hungary (Szadoczky et al., 1998), from 18 to 23.8 yo in Germany (Wittchen et al., 2003) and 25 yo in Australia (Morgan et al., 2005). The age of onset of manic episodes is usually 6 to 8 years before depressive episodes. There is often a 5 to 10 years interval before correct diagnosis is obtained. After a first episode of mania, most of the patients show a low functional recovery. Although the overt symptoms are relatively well controlled, continued impairments in the overall quality remain. This fact concerns both BPAD I and BPAD II. BPAD II has been considered for a long time as a minor expression of the classic BPAD I. Recently, important studies have focused on the natural history of BPAD II. Judd et al. (2003) have followed a cohort of BPAD II patients during a mean of 13.4 years of prospective follow-up. They showed that patients were symptomatic 53.9% of all follow-up weeks. Most important, depressive symptoms (50,3% of the weeks) dominated the course over hypomanic (1,3% of the weeks) and cycling/mixed (2.3% of the weeks) symptoms. They concluded that BPAD II is a chronic disease with a high rate of major depressive episodes but also periods involving minor or subsyndromal symptoms, as already suggested by Angst and Akiskal (see above).
One of the major concerns about BPAD remains the suicide risk. According to epidemiologic studies, at least 25% of patients with BPAD attempt suicide and 10% to 15% will complete suicide, explaining in part the fact that the mortality rate of the disease is two to three times higher than that of the general population (Jamison, 1998). Furthermore, the rate of suicidal behavior among BPAD patients (including BP AD I and BP AD II) is significantly higher than that of UP AD patients. Rihmer and Pestality (1999) have combined epidemiologic studies on the suicide risk in UPAD, BPAD I and BPAD II. They found that the lifetime history of suicide attempts is significantly higher in BPAD II patients than in BPAD I patients. When considering suicide completers among a population of BPAD and UPAD patients with primary major depression at the time of their suicide in two independent studies, Rihmer and Pestality found that 46% in the first study and 36% in the second study had a diagnosis of BPAD II (compared to 1%-8% of BPAD I patients and 53%-56% of UPAD patients). Given the fact that the lifetime prevalence rate of BPAD II is relatively lower than UPAD, the authors suggested that BPAD II represented a high risk of completed suicide among the population of primary major mood disorder. Because of the high risk of recurrence and suicide, long-term prophylactic treatment is indicated.
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