Table 2.
Differences in the clinical course between BD-I and BD-II patients.
| Variable | BD-I | N | BD-II | N | P | β | SE |
|---|---|---|---|---|---|---|---|
| Age at first episode (years) | 21 (5) | 233 | 21 (6) | 75 | 0.52 | 0.10 | 0.15 |
| Age at first manic episode (years) | 25 (7) | 230 | 26 (8) | 70 | 0.75 | 0.05 | 0.14 |
| Age at first depressive episode (years) | 22 (5.5) | 230 | 21 (6) | 75 | 0.59 | 0.08 | 0.16 |
| Duration of illness (years) | 23 (11) | 233 | 16 (9) | 75 | 2.83 × 10−03 | 0.36 | 0.12 |
| Duration of depressive episodes (weeks) | 16 (8) | 247 | 12 (8) | 75 | 0.14 | 0.21 | 0.14 |
| Number of depressive episodes/illness duration | 0.86 (0.57) | 229 | 0.78 (0.58) | 75 | 0.27 | 0.17 | 0.16 |
| Number of (hypo)manic episodes/illness duration | 0.52 (0.38) | 232 | 0.77 (0.65) | 75 | 0.029 | −0.35 | 0.16 |
| Number of suicide attempts/illness duration (median) | 0 (0) | 233 | 0 (0) | 75 | 0.046 | 0.20 | 0.10 |
| Number of suicide attempts/illness duration (mean) | 0.04 (0.14) | 233 | 0.02 (0.08) | 75 | 0.046 | 0.20 | 0.10 |
| Variable | BD-I | N | BD-II | N | P | OR | 95% CI |
|---|---|---|---|---|---|---|---|
| Depressive polarity of the first episode | 102 (43.78) | 233 | 38 (50.7) | 75 | 0.22 | 0.75 | 0.48–1.18 |
| ECT during depressive episodes | 9 (3.64) | 247 | 1 (1.33) | 75 | 0.42 | 2.41 | 0.28–20.95 |
| Medication during depressive episodes | 237 (95.18) | 249 | 61 (81.33) | 75 | 0.010 | 3.93 | 1.38–11.20 |
| Hospitalization during depressive episodes | 50 (20.16) | 248 | 3 (4.00) | 75 | 2.45 × 10−03 | 6.41 | 1.93–21.35 |
| Incapacity during depressive episodes | 158 (69.30) | 228 | 33 (45.83) | 72 | 7.07 × 10−04 | 2.51 | 1.47–4.28 |
| Suicide attempted (ever) | 65 (25.79) | 252 | 11 (14.67) | 75 | 0.040 | 2.46 | 1.04–5.79 |
| Serious or extreme suicide attempt | 18 (7.14) | 252 | 2 (2.66) | 75 | 0.13 | 3.44 | 0.70–17.03 |
| Seasonality | 139 (58.65) | 237 | 36 (49.31) | 73 | 0.043 | 1.73 | 1.02–2.95 |
BD bipolar disorder, SE standard error, N sample size for the variable (before correction for covariates), OR odds ratio, 95% CI 95% confidence interval, ECT electroconvulsive therapy. Bonferroni-corrected threshold for significance: α = 0.05/37 = 1.35 × 10−03.
Quantitative variables were analyzed in linear, dichotomous variables in logistic models. BD type was the independent variable in all models. We used the following covariates: quantitative variables, sex; dichotomous variables, sex and age. All quantitative variables have been transformed for the analyses using inverse rank-based normalization to generate normally distributed residuals. The numbers of episodes and suicide attempts were divided by the illness duration before the transformation. See Supplementary Table S6 for analyses of these variables not divided by illness duration. All quantitative variables are described by median and median absolute deviation of untransformed variables, sample size (N) and percentage are provided for categorical variables. For the number of suicide attempts, mean and standard deviation are also provided. Significant variables are labeled in bold font.