Table 4.

Potential risk factors for depressive symptoms

Study (n)	Measure of Association	Potential risk factor	Outcome: depressive symptoms/disorder
Jackson et al. 2003 [11] (n = 34)	Wilcoxon rank sum test	a) Cognitive impairment (+ vs. −) at hospital d/c b) Cognitive impairment (+ vs. −) at 6 m c) Degree of change in GDS-SF scores over 6 m, impaired vs. non-impaired	GDS-SF scores a) mean 6 vs. 4 at hospital d/c, p = 0.04 (27% vs. 8% depressed) b) mean 6 vs. 3 at 6 m, p = 0.02 (36% vs. 17% depressed) c) −0.2 vs. 0.5, p = 0.76
Samuelson et al. 2007 [12] (n = 226)	Mann-Whitney U Spearman’s correlation Mann-Whitney U	a) Time since hospital d/c (5 days vs. 2 m) b) Recall of “extremely stressful” ICU nightmares 5 days post-ICU c) Recall of “extremely stressful” ICU fearfulness 5 days post-ICU d) Type of ICU memory (e.g., factual vs. delusional) 5 days post-ICU e) IES-R score at 2 m (PTSD symptoms) f) Recall of “extremely stressful” ICU nightmares (+ vs. − ) 5 days post-ICU g) Recall of “extremely stressful” ICU fearfulness (+ vs. − ) 5 days post-ICU	a) median HADS-D 4 vs. 1, p < 0.0001 b) r > 0.2 (with HADS-D at 2 m), p < 0.01 c) r > 0.2 (with HADS-D at 2 m), p < 0.01 d) n.s. e) r = 0.66 (with HADS-D at 2 m), p < 0.0001 f) median HADS-D 4 vs. 1 at 2 m, p = 0.001 g) median HADS-D 5 vs. 1 at 2 m, p = 0.02
Jones et al. 2001 [13] (n = 30-45)	χ2 Univariate ANOVA	a) ICU diagnostic group b) No factual memories of ICU + “delusional memories” vs. factual memories of ICU + “delusional memories” vs. no “delusional memories” 2 weeks post-ICU c) ICU LOS, APACHE II, days of sedation/opiates	a) p = 0.23 b) mean HADS-D 13 vs. 4 vs. 3 at 2 wks., p = 0.0001 c) n.s. at 2 or 8 weeks
Rattray et al. 2005 [14] (n = 80)	Repeated measures ANOVA Pearson’s correlation Multivariable regression	a) Time since hospital d/c (d/c vs. 6 m vs. 12 m) b) Female sex c) Age d) APACHE II e) ICU LOS f) Hospital LOS g) Recall of ICU experiences (hospital d/c) h1 ) HADS-D (hospital d/c) h2) Frightening ICU memories(hospital d/c) h3) Recall of ICU experiences (hospital d/c) h4) Satisfaction with ICU care (hospital d/c) i1) HADS-D (hospital d/c) i2) Awareness of ICU surroundings (hospital d/c) i3) Recall of ICU experiences (hospital d/c) i4) Satisfaction with ICU care (hospital d/c)	a) mean HADS-D 7 vs. 5 vs. 5, p = 0.001 b) r = 0.27 with HADS-D at hospital d/c, p < 0.02 c) n.s. d) n.s. e) n.s. f) n.s. g) r = −0.26 with HADS-D at 6 m, p = 0.01 h1) βst = 0.44 with HADS-D at 6 m, p < 0.001 h2) βst = 0.06 with HADS-D at 6 m, p = 0.54 h3) βst = −0.21 with HADS-D at 6 m, p = 0.05 h4) βst = −0.05 with HADS-D at 6 m, p = 0.65 i1) βst = 0.40 with HADS-D at 12 m, p < 0.001 i2) βst = −0.02 with HADS-D at 12 m, p = 0.88 i3) βst = −0.10 with HADS-D at 12 m, p = 0.37 i4) βst = −0.09 with HADS-D at 12 m, p = 0.46
Boyle et al. 2004 [15] (n = 52)	Student’s paired t-test	a) Time since hospital d/c (1 m vs. 6 m) b) Chronic pain + vs. − at 6 m (n = 47)	a) mean CES-D 19 vs. 14, p = 0.03 b) mean CES-D 14 vs. 10 at 6 m, p = 0.67
Jones et al. 2003 [17] (n = 114)	Fisher’s exact test One-way ANOVA Fisher’s exact test	a) No self-help rehabilitation manual (n = 114) b) Antidepressant + no self-help rehabilitation manual vs. antidepressant + self-help manual (n =21) c) No self-help rehabilitation manual (n = 102)	a) 25% vs. 12% (HADS-D >11 at 2 m), p = 0.07 b) higher mean HADS-D at 2 m, p = 0.004 c) 12% vs. 10% (HADS-D>11 at 6 m), n.s.
Weinert et al. 2006 [18] (n = 90-153)	Least squares regression Repeated-measures regression analysis Relative risk (RR) Spearman’s correlation	a) Age b) Male sex c) Pre-ICU physical functioning d) Antidepressant in 6 m before ICU e) Proxy report of depressed mood in m before ICU f) Time since hospital d/c (2 m, 6 m) g) Age h) Male sex i) Pre-ICU physical functioning j) Antidepressant in 6 m before ICU k) Proxy report of depressed mood in m before ICU l) Depression at 2 m post-ICU m) Change in physical functioning from pre-ICU baseline to 2 m post-ICU n) Improvement in physical functioning from 2 m to 6 m post-ICU	CES-D scores (square root) at 2 m a) β = −0.006, p = 0.46 b) β = −0.12 p = 0.66 c) β = −0.01, p = 0.01 d) β = 0.53, p = 0.09 e) β = 1.07, p = 0.002 CES-D scores (square root) at 2 and 6 m f) β = −0.007, p = 0.97 g) β = −0.007, p = 0.45 h) β = 0.07, p = 0.78 i) β = −0.01, p = 0.03 j) β = 0.54, p = 0.08 k) β = 0.95, p = 0.004 l) Depression at 6 m, RR = 4.2, 95% CI = 2-7.7 m) n.s. n) r = −0.45, p < 0.001
Sukantarat et al. 2007 [20] (n = 51)	Student’s paired t-test Spearman’s correlation	a) Time since hospital d/c (3 m vs. 9 m) b) HADS anxiety score at 3 and 9 m c) IES intrusion and avoidance scores (PTSD symptoms) at 3 and 9 m d) Physical symptom score at 3 m and 9 m e) Age, ICU LOS, APACHE II score, TISS points	a) 35% vs. 47% (HADS-D score > 8), p = 0.52 b) HADS-D at same time points, p < 0.0001 c) HADS-D at same time points, p < 0.002 d) HADS-D at same time points, p < 0.001 e) n.s.
Eddleston et al. 2000 [21] (n = 143)	Fisher’s exact test	Female vs. male sex	12% vs. 8%, n.s.
Kress et al. 2003 [23] (n = 32)	Student’s paired t-test or Mann Whitney U	Control vs. daily sedative interruption	BDI-II mean score 17 vs. 14, p = 0.36

Abbreviations (in alphabetical order): ANOVA = analysis of variance; APACHE II = Acute Physiology and Chronic Health Evaluation II; BDI-II = Beck Depression Inventory-II; β = regression coefficient; β_st = standardized linear regression coefficient in multivariable model; CES-D = Center for Epidemiologic Studies Depression Scale; CI = confidence interval; d/c = discharge; df = degrees of freedom; GDS-SF = Geriatric Depression Scale-Short Form; HADS = Hospital Anxiety and Depression Scale; HADS-D = HADS depression subscale; ICU = intensive care unit; IES = Impact of Events Scale; IES-R = Impact of Events Scale-Revised; LOS = length of stay; m = month(s); n.s. = not significant; PTSD = posttraumatic stress disorder; TISS = Therapeutic Intervention Scoring System; “-” = not reported.