**5. Conclusions**

Preliminary findings show that postoperative CBT is e ffective as an add-on treatment to DBS in patients with therapy-resistent OCD. Further studies are necessary to establish the place of CBT after DBS. These studies should have larger sample sizes and designs that are adequate to quantify the added effects of both CBT as well as pharmacotherapy. In order to let patients benefit optimally from the experience and expertise of behavioral therapists working in DBS clinics, novel ways of administering CBT, such as administered by telephone, videoconferencing or online, should also be studied.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2077-0383/9/8/2383/s1, Table S1: Quality ratings of the included studies according to the Evidence Project risk of bias tool (Kennedy 2019).

**Author Contributions:** Conceptualization, A.F.G.L.; methodology, A.F.G.L.; formal analysis, M.G.; writing—original draft preparation, M.G.; writing—review and editing, T.B.v.d.V., K.S., L.A., M.P.; supervision, A.F.G.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
