Table 2.
Group Differences in Composite Scale of Morningness (CSM) Mean Total Scores and in Proportions of Participants Classified with Evening Chronotype, Based Upon Original and Modified CSM Scale Thresholds.
| Bipolar Disorder (n=54) | Healthy Control (n=57) | t or χ2 | p-value | |
|---|---|---|---|---|
|
|
||||
| Total CSM Score, Mean (SD) | 33.1 (8.3) | 36.1 (6.9) | 2.1 | 0.04 |
| Evening chronotype classification | ||||
| Original threshold, n (%) | 3 (5.6) | 1 (1.8) | 1.2 | 0.36 |
| ≤ 1 SD threshold, n (%) | 13 (24.1) | 5 (8.8) | 4.8 | 0.04 |
| ≤ ¾ SD threshold, n (%) | 16 (29.6) | 7 (12.3) | 5.1 | 0.03 |
| ≤ ⅔ SD threshold, n (%) | 19 (35.2) | 7 (12.3) | 8.1 | 0.007 |
| ≤ ½ SD threshold, n (%) | 24 (44.4) | 9 (15.8) | 10.9 | 0.002 |
| ≤ ¼ SD threshold, n (%) | 27 (50.0) | 20 (35.1) | 2.5 | 0.13 |
Note. SD = standard deviation. CSM = Composite Scale of Morningness. The original CSM threshold entailed total score of ≤ 22 for evening chronotype. CSM total scores ≤ 1 SD (total ≤ 26.8), ≤ ¾ SD (total ≤ 28.8), ≤ ⅔ SD (total ≤ 29.4), and ≤ ½ SD (total ≤ 30.7) and ≤ ¼ SD (total ≤ 32.7) below our sample mean (34.6) were our modified thresholds for evening chronotypes. Seven bipolar disorder group participants and 4 control group participants were missing CSM total scores. Underlines indicate t- (rather than χ2) values.