Cognitive behavioural treatment of negative symptoms in schizophrenia patients: study design of the TONES study, feasibility and safety of treatment

Currently, there are no convincing treatment strategies for negative symptoms of schizophrenia. On this background, we are conducting the treatment of negative symptoms (TONES) study which addresses the question whether cognitive behavioural therapy (CBT) is efficacious for the reduction of negative symptoms in schizophrenia. The present paper aims at presenting the design of the clinical trial of the study as well as the treatment concept. Further, we investigate the feasibility and the safety of our study treatment. The TONES study is a multicentric, prospective, single-blind, randomised, and controlled trial (RCT). The clinical trial compares CBT (test condition) and cognitive remediation (CR; control condition) with respect to the efficacy in reducing negative symptoms. In order to systematically assess aspects of adherence and feasibility therapists filled in session reports after each session. The safety analysis is performed using the sequential method of Whitehead (The design and analysis of sequential clinical trials, Ellis Horwood, Chichester, 1983). We were able to conduct a systematic recruitment and to include a sample of N = 198 patients which is characterised by negative symptoms of medium severity. The majority of patients accepted the format of a 50-min treatment session. The manualised treatment content seemed to be adequate and the cooperation between patients and therapists was excellent or adequate in approximately 80% of the treatment sessions. Of the 15 severe adverse events 10 occurred in the CBT and 5 in the CR. This difference between the groups was not significant. The study presented here is presumably the first high quality RCT which evaluates CBT with negative symptoms as primary endpoint. On the background of the data presented we conclude that CBT for the reduction of negative symptoms is feasible and can be conducted safely.