Table 1.
Base ratesa and descriptives of major depressive disorder symptoms at baseline and at episode recurrence at 2-, 4-, 6- and 9-year follow-up
| IDS symptom | Baseline (n = 490) | 2 years (n = 302) | 4 years (n = 229) | 6 years (n = 190) | 9 years (n = 154) | |
|---|---|---|---|---|---|---|
| Core symptoms | ||||||
| Depressed mood | Base rate (%) | 267 (55%) | 141 (47%) | 126 (55%) | 94 (50%) | 81 (53%) |
| Mean (s.d.) | 1.63 (0.83) | 1.48 (0.77) | 1.61 (0.79) | 1.54 (0.79) | 1.59 (0.83) | |
| Skew | 0.02 | 0.17 | –0.01 | 0.16 | 0.05 | |
| Anhedonia | Base rate (%) | 137 (28%) | 76 (25%) | 61 (27%) | 54 (28%) | 43 (28%) |
| Mean (s.d.) | 0.99 (0.92) | 0.81 (0.92) | 0.88 (0.92) | 0.93 (0.87) | 0.92 (0.86) | |
| Skew | 0.55 | (0.74) | 0.64 | 0.39 | 0.41 | |
| Non-core symptoms | ||||||
| Fatigue/loss of energy | Base rate (%) | 317 (65%) | 154 (51%) | 134 (59%) | 86 (45%) | 81 (53%) |
| Mean (s.d.) | 1.69 (0.81) | 1.43 (0.88) | 1.62 (0.85) | 1.44 (0.86) | 1.52 (0.78) | |
| Skew | −0.39 | −0.15 | −0.20 | 0.12 | −0.11 | |
| Appetite/weight change | ||||||
| Appetite increase | Base rate (%) | 90 (18%) | 47 (16%) | 37 (16%) | 20 (11%) | 17 (11%) |
| Mean (s.d.) | 1.03 (1.13) | 0.81 (1.06) | 0.86 (1.02) | 0.73 (1.00) | 0.70 (0.97) | |
| Skew | 0.71 | 1.04 | 0.97 | 1.34 | 1.37 | |
| Appetite decrease | Base rate (%) | 55 (11%) | 27 (9%) | 10 (4%) | 14 (7%) | 9 (6%) |
| Mean (s.d.) | 0.77 (0.83) | 0.62 (0.78) | 0.52 (0.69) | 0.55 (0.75) | 0.47 (0.74) | |
| Skew | 0.87 | 1.16 | 1.36 | 1.28 | 1.68 | |
| Weight increase | Base rate (%) | 73 (15%) | 43 (14%) | 46 (20%) | 24 (13%) | 30 (20%) |
| Mean (s.d.) | 0.74 (0.93) | 0.67 (0.92) | 0.85 (0.97) | 0.67 (0.92) | 0.83 (1.05) | |
| Skew | 1.00 | 1.17 | 0.79 | 1.26 | 0.92 | |
| Weight decrease | Base rate (%) | 77 (16%) | 34 (11%) | 23 (10%) | 20 (11%) | 19 (12%) |
| Mean (s.d.) | 0.77 (1.03) | 0.58 (0.90) | 0.61 (0.96) | 0.57 (0.87) | 0.62 (0.91) | |
| Skew | 1.03 | 1.41 | 1.42 | 1.40 | 1.25 | |
| Sleep disturbance | ||||||
| Insomnia | Base rate (%) | 173 (35%) | 88 (29%) | 76 (33%) | 69 (36%) | 51 (33%) |
| Mean (s.d.) | 1.25 (0.77) | 1.14 (0.78) | 1.27 (0.81) | 1.26 (0.73) | 1.24 (0.75) | |
| Skew | 0.34 | 0.52 | 0.38 | 0.31 | 0.29 | |
| Hypersomnia | Base rate (%) | 75 (15%) | 43 (14%) | 27 (12%) | 19 (10%) | 20 (13%) |
| Mean (s.d.) | 0.69 (0.85) | 0.65 (0.87) | 0.59 (0.82) | 0.52 (0.79) | 0.66 (0.82) | |
| Skew | 1.13 | 1.29 | 1.42 | 0.31 | 1.22 | |
| Psychomotor disturbance | ||||||
| Psychomotor agitation | Base rate (%) | 203 (41%) | 107 (35%) | 88 (38%) | 56 (30%) | 44 (29%) |
| Mean (s.d.) | 1.20 (0.91) | 1.06 (0.94) | 1.12 (0.95) | 0.90 (0.89) | 0.88 (0.84) | |
| Skew | 0.07 | 0.30 | 0.22 | 0.43 | 0.30 | |
| Psychomotor retardation | Base rate (%) | 184 (38%) | 96 (32%) | 81 (35%) | 65 (34%) | 51 (33%) |
| Mean (s.d.) | 1.06 (0.97) | 0.91 (0.98) | 1.02 (0.97) | 0.94 (0.98) | 0.91 (0.90) | |
| Skew | 0.29 | 0.56 | 0.37 | 0.46 | 0.29 | |
| Worthlessness/guilt | Base rate (%) | 226 (46%) | 142 (47%) | 95 (42%) | 85 (45%) | 69 (45%) |
| Mean (s.d.) | 1.67 (1.17) | 1.62 (1.22) | 1.61 (1.14) | 1.63 (1.21) | 1.62 (1.21) | |
| Skew | −0.03 | −0.04 | 0.12 | −0.01 | 0.02 | |
| Concentration difficulties | Base rate (%) | 239 (49%) | 122 (40%) | 96 (42%) | 70 (37%) | 63 (41%) |
| Mean (s.d.) | 1.55 (0.83) | 1.40 (0.83) | 1.40 (0.83) | 1.33 (0.79) | 1.37 (0.79) | |
| Skew | 0.16 | 0.29 | 0.22 | 0.33 | 0.20 | |
| Suicidal ideation | Base rate (%) | 102 (21%) | 50 (17%) | 45 (20%) | 35 (18%) | 34 (22%) |
| Mean (s.d.) | 0.80 (0.85) | 0.68 (0.77) | 0.72 (0.83) | 0.71 (0.78) | 0.85 (0.82) | |
| Skew | 0.72 | 0.75 | 0.79 | 0.62 | 0.57 | |
IDS, Inventory of Depressive Symptomatology.
a.
The base rate indicates the number of people scoring above the diagnostic threshold based on the Likert scale rating: 0 and 1 scored as 0 (symptom not present); 2 and 3 scored as 1 (symptom present).