Eur Arch Psychiatry Clin Neurosci (2011) 261:341–347 and medications taken were compared between patients with one or more episode of hypomania using the 4-day length criterion, and those with one or more episode of hypomania only if a shorter criterion was used (4-day vs. 3-day length, 4-day vs. 2-day length, and 4 day vs. 1-day length). A P value of less than 0.05 was considered sta- tistically signiﬁcant for all tests. SPSS 18.0 was used for all calculations. Results Data were available from 410 patients, 247 with a diag- nosis of bipolar I disorder, 146 with a diagnosis of bipolar II disorder, and 17 with a diagnosis of bipolar NOS. Since the group with a diagnosis of bipolar NOS was so small, they were excluded from this analysis leaving 393 patients. 343 The 393 patients returned 75,284 days of data (mean 191.6 days). Of the 393 patients 266 (68%) were recruited from a university mood clinic, and 127 (32%) from a pri- vate practice. The demographic characteristics of those with BP I and BP II disorder are shown in Table 1. Patients with bipolar I disorder had more hospitalizations (2.8 vs. 1.4, P = 0.002), took antidepressants less frequently (45 vs. 63%, P \ 0.001), lamotrigine less frequently (33 vs. 45%, P = 0.018), and lithium more frequently (32 vs. 21%, P = 0.018). No other signiﬁcant differences in demographic characteristics were found between patients with bipolar I and bipolar II disorder. The impact of changing the minimum length requirement for an episode of hypomania is shown in detail in Table 2. When the minimum episode length was decreased from 4 to 2 days, the percent of days spent in a hypomanic episode by each patient nearly doubled (4.5–8.2%), and the number of Table 1 Comparison of demographics of patients with diagnosis of bipolar I or bipolar II disorder Bipolar I (N = 247) Bipolar II (N = 146) Total (N = 393) Degrees of freedom (DF) P Age (mean years, SD) Age of onset (mean years, SD) Years of illness (mean years, SD) Hospitalizations (mean N, SD) Gender Female (N, %) Male (N, %) Education level High school (N, %) Some college (N, %) College graduate (N, %) Employment status Disabled (N, %) Working full-time (N, %) Other (N, %) Marital status Married (N, %) Single (N, %) Divorced (N, %) Number of daily medications (mean N, SD) Taking mood stabilizer (N, %) Taking lithium (N, %) Taking valproate (N, %) Taking lamotrigine (N, %) Taking antidepressant (N, %) Taking antipsychotic (N, %) Taking benzodiazepine (N, %) Taking sleep medication (N, %) a Student’s t test, equal variances not assumed b Pearson Chi-Square test Diagnosis 39.4 (11.2) 22.6 (9.7) 16.9 (11.1) 2.8 (4.2) 160 (65) 87 (35) 33 (14) 75 (33) 121 (53) 66 (29) 102 (44) 61 (27) 107 (46) 90 (39) 37 (15) 2.8 (1.6) 204 (83) 78 (32) 49 (20) 82 (33) 110 (45) 114 (46) 51 (21) 18 (7) 38.2 (11.4) 20.9 (10.9) 17.7 (12.3) 1.4 (3.2) 108 (74) 38 (26) 12 (9) 45 (33) 79 (58) 25 (19) 72 (56) 33 (25) 66 (50) 52 (39) 14 (11) 2.6 (1.5) 111 (76) 30 (21) 32 (22) 66 (45) 92 (63) 57 (39) 35 (24) 7 (5) 39.0 (11.3) 22.0 (10.2) 17.2 (11.5) 2.3 (3.9) 268 (68) 125 (32) 45 (12) 120 (33) 200 (55) 91 (25) 174 (49) 94 (26) 173 (47) 142 (39) 51 (14) 2.7 (1.6) 315 (80) 108 (28) 81 (21) 148 (38) 202 (51) 171 (44) 86 (22) 25 (6) 299.1a 240.4a 241.7a 326.1a 1b 2b 2b 2b 322.8a 1b 1b 1b 1b 1b 1b 1b 1b 0.299 0.133 0.535 0.001 0.059 0.274 0.079 0.370 0.330 0.115 0.018 0.622 0.018 \0.001 0.169 0.441 0.328 123