|1.9 Natural Course of Bipolar Disorder|
Having an understanding and knowledge of the natural course of the disorder, helps to understand how effective different treatments are, and at the same time provide information that helps the design of prospective naturalistic studies that investigate syndromal outcome. This is especially the case in naturalistic studies when there is no control group available to compare differences in syndromal outcome.
Angst and Sellaro (2000), in a review of the natural course of bipolar disorder conclude with a pessimistic view that the prognosis for the majority of the patients remains poor. The valuable studies reviewed prior to the drug treatment era reported information on both the natural length/duration of episodes as well as the number of episodes a patient is going to experience over his life time. The duration of manic episodes was reported to be anything from a median of 4-6 months (Mendel, 1881, Wertham, 1929) or a higher mean of 6-8 months (Kraepelin, 1913, Panse, 1924). Given that the mean values can be distorted by patients who have a rapid cycling or a chronic course the median values are probably more representative in terms of understanding the typical number of episodes. Also two early studies (Rennie, 1942, Kinkelin, 1954) suggested that later manic episodes would tend to last longer.
Contemporary naturalistic studies that essentially report data from medicated patients report briefer episode durations. The data from the longest naturalistic follow up (1959-1985), the Zurich study (Angst and Preisig, 1995) reported a median length of both pure manic and depressive episodes of three months (mean= 4.3 months) with no gender differences. The intervals between the first three episodes have also been found to shorten but later there appears to be an irregular rhythm of about 0.4 episodes per year, which is however highly variable across patients (Angst and Sellaro, 2000) and of course nowadays different treatment modalities.
Lifetime outcome appears to be poor both in early and contemporary studies. In the longest follow up to date the Zurich study, out of 219 bipolar I patients with a median age of 68 years old at follow up, only 16% of patients had recovered, 52% still suffered from recurrent episodes, and 32% had become chronically ill or had passed away by committing suicide. This data primarily refers to bipolar I patients. The few studies of the bipolar II sub-type conclude that there are no differences in the life-time course between the two (Angst 1986; Coryell, Keller et al. 1989).
Angst, J. & Sellaro, R. 2000. Historical perspectives and natural history of bipolar disorder. Biol Psychiatry, 48, 445-57.