Bipolar Disorders: Mixed States, Rapid-Cycling, and Atypical Forms

144 F. BenazziStatisticsMeans were compared with the t-test, proportions were compared by the twosampletest of proportion. Univariate and multivariate logistic regression wasused to study associations. Two-way ANOVA was used to study interaction.Maximum-likelihood logit estimation was used for discriminant analysis.STATA Statistical Software, Release 7, was used (Stata Corporation, CollegeStation, TX, USA). P-values were two-tailed, and the probability level wasP < 0.05.ResultsFrequency of AD was 182/433 (42.0%). AD versus non-AD (Table 6.1) hadsignificantly more BP-II, females, lower age, lower age of onset, more axis Icomorbidity, fewer psychotic features, more DMX, more BP family history, andmore hypomanic and atypical symptoms.To test if AD associations with female gender, early onset, DMX, and BP familyhistory were specific features of AD, or were due to its association with BP-II(which could be a confounding factor, as it was associated with all these variables),multivariate logistic regression controlled for BP-II was used. Logistic regressionof AD versus females gender found OR ¼ 1.9, z ¼ 3.2, P ¼ 0.001, and when controlledfor BP-II found OR ¼ 1.9, z ¼ 2.9, P ¼ 0.003. Logistic regression of ADversus onset found OR ¼ 0.9, z ¼ 5.4, P ¼ 0.000, and when controlled for BP-IIfound OR ¼ 0.9, z ¼ 4.2, P ¼ 0.000. Logistic regression of AD versus DMX foundOR ¼ 3.0, z ¼ 5.5, P ¼ 0.000, and when controlled for BP-II found OR ¼ 2.4,z ¼ 4.2, P ¼ 0.000. Logistic regression of AD versus BP family history foundOR ¼ 2.1, z ¼ 3.0, P ¼ 0.002, and when controlled for BP-II found OR ¼ 1.6,z ¼ 1.8, P ¼ 0.062. To test if the association between AD and axis I comorbiditywas specific for AD, or was instead related to a common early age of onset,multivariate logistic regression was used. Logistic regression of AD versus axis Icomorbidity found OR ¼ 1.6, z ¼ 2.5, P ¼ 0.011, and when controlled for onset,found OR ¼ 1.4, z ¼ 1.6, P ¼ 0.093.To test if the association between AD and BP-II was related to early onset (bothhad an early onset), multivariate logistic regression was used. Logistic regression ofAD versus BP-II found OR ¼ 3.3, z ¼ 5.5, P ¼ 0.000, and when controlled foronset, found OR ¼ 2.5, z ¼ 4.0, P ¼ 0.000. Two-way ANOVA was also used tofind if the lower age of onset in AD versus non-AD was related to an interactionbetween AD and BP-II. The result was that AD had F ¼ 23.2, P ¼ 0.000, BP-II hadF ¼ 26.9, P ¼ 0.0000, and there was an interaction between AD and BP-II (F ¼ 4.7,P ¼ 0.0306). Discriminant analysis of BP-II, female gender, early onset, DMX, and