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Table 1 Descriptive statistics depicting the differences between groups NAC and placebo on demographic and illness characteristics.

From: Maintenance N-acetyl cysteine treatment for bipolar disorder: A double-blind randomized placebo controlled trial

Characteristics Descriptive statistic Total sample n = 149 NAC n = 76 Placebo n = 73 Test statistic Value df P
Age M(SD) 45.8 (11.4) 47.1 (10.9) 44.4 (11.8) t-test 1.46 147 .146
Gender %Female % (n) 67.8 (101) 78.9 (60) 56.2 (41) χ2 8.85 1 .003
Diagnosisa         
   Bipolar I disorder % (n) 69.6 (103) 73.7 (56) 65.3 (47) χ2 1.24 1 .266
   Bipolar II disorder % (n) 29.7 (44) 25.0 (19) 34.7 (25)     
   Bipolar NOS % (n) 1 (0.7) 1.3 (1) 0.0 (0)     
Suicidality %Yes % (n) 70.9 (105) 69.7 (53) 72.2. (52) χ2 0.11 1 .739
Age of first symptoms M(SD) 22.0 (10.6) 22.2 (11.8) 21.9 (9.2) t-test 0.17 138 .867
Age of diagnosis M(SD) 35.9 (11.6) 37.4 (12.0) 34.4 (11.2) t-test 1.58 141 .115
Duration of illness since diagnosis (years)b M(SD) 10.0 (9.4) 9.6 (9.3) 10.5 (9.6) t-test -0.74 141 .462
  Mdn 7.0 6.0 7.5     
Number of psychiatric hospitalisationsc M(SD) 3.0 (4.4) 3.2 (5.3) 2.8 (3.3) t-test -0.31 141 .759
  Mdn 1.0 2.0 1.0     
Number of manic episodes >10 % (n) 53.5 (76) 54.8 (40) 52.2 (36) χ2 0.10 1 .754
Number of depressive episodes >10 % (n) 78.3 (112) 80.8 (59) 75.7 (53) χ2 0.55 1 .459
Smoker %Yes b % (n) 37.1 (49) 30.8 (20) 43.3 (29) χ2 2.21 1 .137
Alcohol use %Yes b % (n) 47.0 (62) 47.7 (31) 46.3 (31) χ2 0.03 1 .870
Alcohol dependence/abuse b % (n) 14.2 (21) 14.5 (11) 13.9 (10) χ2 0.01 1 .919
Substance use %Yes b % (n) 3.0 (4) 4.6 (3) 1.5 (1) χ2 1.10 1 .295
Substance dependence/abuse b % (n) 14.3 (21) 13.3 (10) 15.3 (11) χ2 0.11 1 .736
  1. aChi-square based on two categories (Bipolar I disorder versus other) due to small cell sizes;
  2. b These substances use variables related to status at entry to the maintenance phase of the trial (Week 8). c Inferential statistics based on logarithmic transformed data (plus constant) because of extreme positive skewness. Untransformed descriptive statistics are reported.