Conflicts of interest in invasive brain stimulation research

We read with great interest the recently published manuscript “A narrative review on invasive brain stimulation for treatment-resistant depression” by Dandekar et al.¹ Since major depressive disorder is highly prevalent, associated with significant impairment, and patients who do not respond to therapy face multiple challenges, it is of utmost importance to develop innovative and personalized interventions. The authors reviewed several studies on different treatment modalities, including case reports, cohort studies, open-label, and randomized clinical trials. The conflicting results and limitations of the current studies were discussed, with the authors concluding that “based on current data, invasive neurostimulation therapies may be considered a promising therapy for treatment-resistant depression.”

One important point not raised by the authors is the potential effect of the original investigators’ financial conflicts of interest and industry sponsorship of clinical trials on surgical interventions. Manufacturer-sponsored drug and device trials tend to report more favorable results and conclusions.² The potential impact of conflicts of interest on drug intervention studies and the allegiance effect³ in psychotherapy trials are commonly acknowledged and, more recently, bias in psychiatric neurosurgery research⁴ has been increasingly recognized, although it is still underreported. Invasive brain stimulation involves the use of devices to administer and monitor the clinical effect of treatment, and several companies have a great interest in developing and receiving approval from regulatory agencies.⁵

Due to the non-systematic nature of Dandekar et al.’s review,¹ no formal risk of bias assessment was performed for the included studies and no conclusions can be drawn about the influence of potential biases (including conflicts of interest) on positive outcomes in the reviewed trials. Future systematic reviews should address this important issue and shed further light and transparency on this important field of research. Meanwhile, the lack of data regarding conflicts of interest in narrative reviews should be considered and properly addressed as a limitation.

Disclosure

FAG has received honoraria as speaker/consultant from Abbott, Allergan, Apsen, Daiichi-Sankyo, Libbs, Lundbeck, and Otsuka. EB has received honoraria as speaker/advisory board member from Janssen and Daiichi-Sankyo. All these fundings are unrelated to the current manuscript.