Background. Expressed emotion (EE) is a measure that has been used to assess the quality of the relationship between patient and their key relative. It has been shown to be strongly predictive of clinical outcome in a range of psychiatric and medical disorders. This study investigated the effect of EE on treatment outcome in chronic post-traumatic stress disorder (PTSD).

Methods. A prospective design was adopted. The key relatives of 31 PTSD patients participating in a treatment trial comparing imaginal exposure with cognitive therapy were interviewed and rated on EE prior to treatment allocation. The effect of EE on post-treatment clinical outcomes was assessed.

Results. Sixteen patients (52%) had high EE and 15 (48%) low EE relatives. Patients with high EE relatives showed lesser change scores on the main outcome variable of the trial, the total CAPS score, and on all the secondary outcome variables than those with low EE relatives. Using different multiple regression models the EE scales of criticism and hostility predicted just under 20% of the outcome variance. These two scales were highly correlated and criticism marginally predicted the greatest variance (19·7%).

Conclusions. The results highlight the importance of the quality of the patient's social environment in influencing their response to cognitive and behavioural treatments.