Attachment style as a moderating influence on the efficacy of cognitive-behavioral and interpersonal psychotherapy for depression: A failure to replicate.

Research on aptitude-treatment interactions, or patient characteristics that are associated with better outcome in one treatment than another, can help assign patients to the treatments that will be most personally effective. Theory and one past study suggest that adult attachment style might influence whether depressed patients respond better to cognitive-behavioral therapy (CBT) or interpersonal psychotherapy (IPT). Spurred by inconsistency in past aptitude-treatment interaction research in general, as well as concerns about the reproducibility of psychological research, we sought to replicate and extend the previous study that showed that high attachment avoidance was associated with greater depression reduction in CBT than in IPT and to improve upon that study methodologically. Using longitudinal hierarchical linear modeling, the present study examined whether, among 69 adults randomly assigned to CBT or IPT, rate of change in severity of depression symptoms was predicted by treatment condition, attachment style, and their interaction. We also conducted regression analyses to determine whether posttreatment depression was predicted by the same variables. As expected, CBT and IPT were equivalent in efficacy; however, unlike in the previous trial, there were no moderation effects of attachment. Interestingly, in some analyses, anxious attachment was associated with more positive outcomes and avoidant attachment with more negative outcomes across both treatments. The findings highlight the need for researchers to attempt replications of past studies using methods that might elucidate the reasons for discrepancies in results, and they also suggest that alternative approaches to aptitude-treatment interaction research may be more fruitful.