Table 2.

Depressive symptom severity (PHQ-9) score according to trial arm, in total and stratified by prognostic group

All participantsPrognostic group
Minimal/mildModerateSevere
nMean (SD)nMean (SD)nMean (SD)nMean (SD)
3 months
  Intervention5948.26 (6.02)4396.59 (5.04)8011.64 (5.51)7514.40 (6.39)
  Control6689.16 (6.51)4837.29 (5.60)11212.69 (5.62)7316.10 (6.49)
12 months
  Intervention5637.77 (5.85)4216.33 (5.01)7410.53 (5.68)6813.69 (6.11)
  Control6028.44 (6.19)4416.82 (5.26)10312.10 (6.14)5814.28 (6.64)
Total18681357288223
P-valueP-valueP-valueP-value
3 months
  Difference in mean outcome between arms (95% CI)a−0.880.003−0.620.04−0.840.29−1.980.06
(−1.45 to −0.31)(−1.21 to −0.03)(−2.40 to 0.72)(−4.00 to 0.04)
  Sensitivity analysisb−0.87 (−1.43 to −0.30)0.003−0.62 (−1.21 to −0.04)0.04−1.08 (−2.66 to 0.49)0.18−2.16 (−4.20 to −0.12)0.04
  Sensitivity analysisc−1.98 (−4.00 to 0.04)0.06
  CACE analysisd−5.23 (−10.9 to 0.44)0.07
  SMDa,e−0.16 (−0.26 to −0.05)−0.18 (−0.36 to −0.01)−0.36 (−1.02 to 0.31)−0.56 (−1.12 to 0.01)
12 months
  Difference in mean outcome between arms (95% CI)a−0.59 (−1.18 to 0.01)0.05−0.35 (−0.94 to 0.25)0.26−1.35 (−3.02 to 0.32)0.11−0.10 (−2.29 to 2.08)0.93
  Sensitivity analysisb−0.57 (−1.16 to 0.02)0.06−0.34 (−0.93 to 0.25)0.26−1.47 (−3.14 to 0.21)0.09−0.19 (−2.43 to 2.04)0.87
  Sensitivity analysisc−0.10 (−2.29 to 2.08)0.93
  CACE analysisd−1.65 (−7.61 to 4.31)0.59
  SMDa,e−0.10 (−0.21 to 0.002)−0.10 (−0.28 to 0.08)−0.58 (−1.29 to 1.14)−0.03 (−0.64 to 0.58)
  • a Estimated difference in mean outcome between intervention and control arms using linear mixed-effects regression with random intercepts for individuals and adjusted for baseline outcome measure, general practice, time and prognostic group (for all partcipants only); mean outcome was constrained to be equal at baseline.

  • b Same as ‘a’, adjusted for factors associated with non-response at 3 and 12 months (age, sex, highest level of education, current employment status, hold a health care card, long term illness, live alone, self-rated health, manage on available income, number of times visited a psychiatrist or counsellor in past 12 months, and current use of antidepressants).

  • c Same as ‘a’, adjusted for imposed clustering by nurse in the intervention arm in the severe prognostic group only; 6 nurses (cluster size [range] 1 to 31, median = 14 patients). Estimated intra-cluster correlation for imposed clustering was zero.

  • d Adherence-adjusted analysis for severe group only (adherence = completed all eight sessions).

  • e SMD was calculated as the difference in means between arms and divided by the pooled SD at baseline for all participants (SD = 5.71); minimal/mild (SD = 3.39); moderate (SD = 2.34); and severe (SD = 3.56) group. CACE = complier average causal effect. PHQ-9 = 9-item Patient Health Questionnaire. SD = standard deviation. SMD = standardised mean difference.