Descriptive statistics and correlation coefficients are listed in
Table 2. Estimates of direct effects from mediation models using
patient-rated therapeutic alliance are displayed in Table 3. Direct
effects from serial mediation analyses showed that early CALPAS
ratings were positively predicted by pretreatment Agreeableness,
but not by Neuroticism, Extraversion, Openness, or Conscientiousness.
In all models, early CALPAS ratings positively predicted
late CALPAS ratings. Moreover, in all models, late CALPAS
negatively predicted treatment outcome. Neuroticism was the only
pretreatment personality trait that showed a direct effect on
treatment outcome, such that higher Neuroticism predicted
poorer treatment outcomes, as measured by posttreatment BDI-II
scores (p¼.044); however, this effect was not replicated in models
predicting posttreatment Ham-D scores. Estimates of indirect effects
from all mediation models are displayed in Table 4. The indirect
effect of Agreeableness on treatment outcome via early and
late alliance was significant. No other significant serial mediation
effects were observed for the remaining five-factor model domains.
We did observe additional evidence for the indirect effects
of Extraversion, Openness, and Agreeableness; however, these
results varied depending on the time at which CALPAS ratings
were obtained and our measure of depressive symptoms. For example,
Openness showed significant indirect effects on posttreatment
depression scores via late ratings of alliance. Extraversion
similarly showed significant indirect effects on posttreatment depression
scores via late ratings of alliance; however, this was onlythe case for models predicting posttreatment BDI-II scores. In
contrast, Agreeableness showed significant indirect effects on
posttreatment depression scores via early ratings of alliance, but
only for the model predicting posttreatment BDI-II scores. Models
that showed significant indirect effects (i.e., Ham-D models for
Openness and Agreeableness; BDI-II models for Extraversion,
Openness, and Agreeableness) were followed up with multiple
group mediation models. These analyses yielded no significant
indirect effects for ADM, IPT, or CBT. Results were omitted for
brevity, but are available upon request.
Results for serial mediation models using therapist-rated
therapeutic alliance yielded few significant direct effects. In all
models, early CALPAS ratings positively predicted late CALPAS
ratings (all pso.001). Patient Neuroticism was the only pretreatment
personality trait that showed a direct effect on treatment
outcome, such that higher Neuroticism predicted poorer treatment
outcomes, as measured by residualized BDI-II scores
(p¼.025); however, this effect was not replicated in models predicting
residualized Ham-D scores. No direct effects were observed
between patient personality and therapist-rated CALPAS scores (all
ps4.152). In addition, no significant indirect effects emerged. Full
results for these analyses are available upon request.