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However, sleep disturbances are often overlooked in clinical psychiatric settings, and non-pharmacological treatment options are not initiated. Cognitive behavioral therapy for insomnia (CBT-I) has been shown to effectively ameliorate sleep disturbances in schizophrenia but is yet to be assessed in treatment-resistant schizophrenia. In the present study, we aim to investigate the efficacy of CBT-I versus standard cognitive behavioral therapy (CBT), an active control intervention.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Sixty patients diagnosed with treatment-resistant schizophrenia and comorbid sleep disturbance will be included in this randomized intervention study. Included patients will be randomized to 8\u201310 sessions of psychotherapy with either CBT-I (active intervention) or regular CBT (active control) following baseline. At baseline and 12-week follow-up, patients will be assessed with clinical interviews (Positive and Negative Syndrome Scale), self-reported measures (e.g., Insomnia Severity Index), and polysomnography. The 24-week follow-up will include the same assessments apart from polysomnography. The active intervention group will receive an individual course of treatment with CBT-I focused on the patients\u2019 sleep patterns, while the active control group will receive an individual course of treatment with standard cognitive behavioral therapy (CBT) focused on patients\u2019 psychopathology. It is hypothesized that while both groups will show improvements on central outcome measures, CBT-I will show greater improvements in sleep disturbances. Further, it is hypothesized that the improvement in sleep disturbances will correlate with an improvement in positive symptoms. Lastly, it is anticipated that the CBT-I group will show objective improvements in sleep architecture, such as sleep latency, wake after sleep onset, sleep efficiency, and total sleep time, compared to the CBT group.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>Should CBT-I prove efficacious in improving sleep disturbances in treatment-resistant schizophrenia, it would provide an avenue for a cost-beneficial, short-term, and implementable non-pharmacological treatment of a severe comorbidity in complex schizophrenia patients. Potential issues pertaining to the completion of the study are discussed.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Trial registration<\/jats:title>\n                    <jats:p>ClinicalTrials.gov NCT06749444.\u00a0Registered on December 27, 2024.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s13063-026-09482-0","type":"journal-article","created":{"date-parts":[[2026,4,17]],"date-time":"2026-04-17T07:39:03Z","timestamp":1776411543000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Cognitive behavioral therapy for insomnia vs. standard cognitive behavioral therapy for sleep and circadian disturbances in treatment-resistant schizophrenia: study protocol for the randomized controlled trial (COSTS)"],"prefix":"10.1186","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-7609-2099","authenticated-orcid":false,"given":"Jeppe Feigenberg","family":"Johansen","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0780-7099","authenticated-orcid":false,"given":"Mette \u00d8degaard","family":"Nielsen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6684-428X","authenticated-orcid":false,"given":"Mette","family":"Kragh","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9868-7028","authenticated-orcid":false,"given":"Jimmi","family":"Nielsen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"297","published-online":{"date-parts":[[2026,4,17]]},"reference":[{"key":"9482_CR1","unstructured":"Harvey AG, Buysse DJ. 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