Table 1.
Descriptive statistics depicting the differences between groups NAC and placebo on demographic and illness characteristics.
| 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 |
aChi-square based on two categories (Bipolar I disorder versus other) due to small cell sizes;
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.