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Table 3 Multiple mixed effects analyses predicting QoL two and six years post-tsunami ( N= 58)

From: Posttraumatic growth, depression and posttraumatic stress in relation to quality of life in tsunami survivors: a longitudinal study

  Global quality of life Health-related quality of life
  T1 T2 T1 T2
  b 95% CI p b 95% CI p b 95% CI p b 95% CI p
Models without interaction variables             
Posttraumatic growth 0.13 −0.04, 0.29 .12 0.11 −0.09, 0.30 .27 0.08 −0.15, 0.31 .48 0.15 −0.09, 0.39 .20
Depression a −0.26 −0.47, −0.05 .02 −0.42 −0.68, −0.16 .002 −0.43 −0.73, −0.12 .007 −0.47 −0.78, −0.15 .004
Posttraumatic stress b −0.42 −0.64, −0.19 < .001 −0.27 −0.54, 0.00 .05 −0.27 −0.59, 0.05 .10 −0.18 −0.51, 0.14 .27
Explained variance c 50.9%    44.3%    34.8%    37.9%   
Model fit: AIC 122.2    141.7    162.8    160.5   
Models with interaction variables             
Posttraumatic growth 0.13 −0.04, 0.30 .12 0.14 −0.05, 0.33 .14 0.13 −0.09, 0.35 .23 0.20 −0.03, 0.43 .09
Depression a −0.33 −0.60, −0.06 .02 −0.44 −0.75, −0.14 .005 −0.66 −1.01, −0.31 .001 −0.59 −0.95, −0.22 .002
Posttraumatic stress b −0.44 −0.68, −0.21 < .001 −0.39 −0.65, −0.14 .003 −0.42 −0.75, −0.09 .01 −0.26 −0.57, 0.06 .11
Depression* Posttraumatic stress 0.07 −0.10, 0.24 .40 0.08 −0.11, 0.26 .41 0.29 0.07, 0.52 .01 0.16 −0.07, 0.38 .17
Posttraumatic growth* Depression −0.12 −0.35, 0.11 .30 −0.51 −0.77, −0.26 < .001 −0.17 −0.49, 0.15 .29 −0.39 −0.70, −0.08 .01
Posttraumatic growth* Posttraumatic stress 0.20 −0.04, 0.45 .10 0.49 0.22, 0.77 .001 0.22 −0.09, 0.54 .16 0.55 0.22, 0.89 .002
Explained variance c 52.9%    58.3%    38.2%    47.4%   
Model fit: AIC 128.2    136.8    162.7    156.4   
  1. Note. Multilevel regression analysis controlled for the effect of mutual family members. All variables were simultaneously entered into the regression model. Posttraumatic growth, depression and posttraumatic stress were standardized before being entered into the model. Figures are regression coefficients (95% confidence intervals in parenthesis). All predictors were measured two years post-tsunami. Explained variance is the percentage reduction in unexplained variance compared to a model without any independent variables. AIC for an empty model was 150.2 and 162.9 for general quality of life at T1 and T2, respectively, and 178.0 and 171.2 for health-related quality of life at T1 and T2, respectively.
  2. AIC = Akaike’s information criterion.
  3. *Interaction between variables.
  4. aLevel of depression as measured by the General Health Questionnaire.
  5. bLevel of posttraumatic stress as measured by the PCL.
  6. cVariance within families was not possible to estimate for quality of life at T2. However, a multiple linear regression analysis without controlling for common family members gave identical estimates and p-values for fixed effects as the mixed effects model.