Objectives: This study aimed to investigate the relationship between trial registration, trial discrepancy from registered protocol, and spin in nonpharmacological trials.
Study design and setting: Recent psychotherapy trials on depression (2015-2018) were analyzed regarding their registration status and its relationship to discrepancies between registered and published primary outcomes and to spin (discrepancy between the nonsignificant finding in a study and an overly beneficial interpretation of the effect of the treatment).
Results: A total of 196 trials were identified, of which 78 (40%) had been registered prospectively and 56 (29%) had been registered retrospectively. In 102 (76%) of 134 registered trials, discrepancies between trial and protocol were present. Of 72 trials with a nonsignificant difference between treatments for the primary outcome, 68 trials (94%) showed spin. Discrepancies from protocol were less frequent in prospectively than in retrospectively registered trials (odds ratio= 0.19; 95% confidence interval [CI]: 0.07-0.52), but regarding the amount of spin, there was no difference between prospectively and retrospectively registered trials (rb = -0.12; 95% CI: -0.41 to 0.19) or between registered and unregistered trials (rb = -0.22, 95% CI -0.49 to 0.08).
Conclusion: Protocol discrepancies and spin have a high prevalence in psychotherapy outcome research. The results show no relation between registration and spin, but prospective registration may prevent discrepancies from protocol.
Keywords: Conflict of interest; Depression; Psychotherapy; Reporting bias; Review; Spin in research.
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