These data also provide the first aggregate international
evidence, to our knowledge, that supports the validity
of the spectrum concept of bipolarity.34 There was
a direct association between increasingly restrictive definitions
of BP and indicators of clinical severity including
symptom severity, role impairment, comorbidity, suicidality,
and treatment. For example, the proportion of
mood episodes rated as clinically severe increased from
42.5% for subthreshold BP to 68.8% for BP-II to 74.5%
for BP-I, and the proportion of cases reporting severe role
impairment ranged from 46.3% for subthreshold BP to
57.1% for BP-I. These findings also confirm those of previous
epidemiologic surveys that have highlighted pervasive
comorbidity between BP and other mental disorders.
10,35 Despite the differences in prevalence rates of
comorbid disorders across countries,