Edinburgh Napier University

  This study investigated the effect of “dose” and the components of Cognitive Behavioral Therapy (CBT) on treatment effects. It is a secondary analysis of the ACTION (Assessment of Cognitive Therapy Instead of Neuroleptics) trial which investigated CBT for people with schizophrenia spectrum disorders that chose not to take antipsychotic medication. Using instrumental variable methods,we found a “dose-response” such that each CBT session attended, reduced the primary outcome measure (the PANSS total score) by approximately 0.6 points (95% CI −1.20 to −0.06, p = 0.031). This suggests that length of therapy is important for those that receive CBT in the absence of antipsychotic medication. Secondly, using principal stratification we examined the process variables that modified treatment effects. Findings revealed that those who received a longitudinal formulation in the first 4 sessions of CBT had poorer treatment effects than those who did not, however this finding was not statistically significant (95% CI −37.244, 6.677, p=0.173). However, it is important to note that these findings were evident in an exploratory analysiswith a small sample. Future larger scale studies are needed to help understand components of effective treatment.