The influence of baseline severity has been examined for antidepressant
medications but has not been studied properly for cognitive–behavioural
therapy (CBT) in comparison with pill placebo.
To synthesise evidence regarding the influence of initial severity on
efficacy of CBT from all randomised controlled trials (RCTs) in which
CBT, in face-to-face individual or group format, was compared with
pill-placebo control in adults with major depression.
A systematic review and an individual-participant data meta-analysis
using mixed models that included trial effects as random effects. We used
multiple imputation to handle missing data.
We identified five RCTs, and we were given access to individual-level
data (n = 509) for all five. The analyses revealed that
the difference in changes in Hamilton Rating Scale for Depression between
CBT and pill placebo was not influenced by baseline severity (interaction
P = 0.43). Removing the non-significant interaction
term from the model, the difference between CBT and pill placebo was a
standardised mean difference of –0.22 (95% CI –0.42 to –0.02,
P = 0.03, I
2 = 0%).
Patients suffering from major depression can expect as much benefit from
CBT across the wide range of baseline severity. This finding can help
inform individualised treatment decisions by patients and their