Moderators of response to cognitive behavioural therapy as an adjunct to pharmacotherapy for treatment-resistant depression in primary care

BACKGROUND: Stratified medicine aims to improve clinical and cost-effectiveness by identifying moderators of treatment that indicate differential response to treatment. Cognitive behavioural therapy (CBT) is often offered as a 'next-step' for patients who have not responded to antidepressants, but no research has examined moderators of response to CBT in this population. We aimed, therefore, to identify moderators of response to CBT in treatment resistant depression.

METHODS: We used linear regression to test for interactions between treatment effect and 14 putative moderator variables using data from the CoBalT randomised controlled trial. This trial examined the effectiveness of CBT given in addition to usual care (n=234) compared with usual care alone (n=235) for primary care patients with treatment resistant depression.

RESULTS: Age was the only variable with evidence for effect modification (p Value for interaction term=0.012), with older patients benefiting the most from CBT. We found no evidence of effect modification by any other demographic, life, illness, personality trait, or cognitive variable (p≥0.2).

CONCLUSIONS: Given the largely null findings, a stratified approach that might limit offering CBT is premature; CBT should be offered to all individuals where antidepressant medication has failed.