Effects of light therapy on mood and insulin sensitivity in patients with type 2 diabetes and depression: Results from a randomized placebo-controlled trial

Annelies Brouwer, Daniel H. van Raalte, Hoang Ton Nguyen, Femke Rutters, Peter M. van de Ven, Petra J.M. Elders, Annette C. Moll, Eus J.W. Van Someren, Frank J. Snoek, Aartjan T.F. Beekman, Marijke A. Bremmer*

*Corresponding author for this work

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OBJECTIVE Depression is common in patients with type 2 diabetes and adversely affects quality of life and diabetes outcomes. We assessed whether light therapy, an antidepressant, improves mood and insulin sensitivity in patients with depression and type 2 diabetes. RESEARCH DESIGN AND METHODS This randomized, double-blind, placebo-controlled trial included 83 patients with depression and type 2 diabetes. The intervention comprised 4 weeks of light therapy (10,000 lux) or placebo light therapy daily at home. Primary outcomes included depressive symptoms (Inventory of Depressive Symptomatology [IDS]) and insulin sensitivity (M-value derived from the results of a hyperinsulinemic-euglycemic clamp). Secondary outcomes were related psychological and glucometabolic measures. RESULTS Intention-to-treat analysis showed that light therapy was not superior to placebo in reducing depressive symptoms (23.9 IDS points [95% CI 29.0 to 1.2]; P = 0.248) and had no effect on insulin sensitivity (0.15 mg/kg*min [95% CI 20.41 to 0.70]; P = 0.608). Analyses incorporating only those participants who accurately adhered to the light therapy protocol (n = 51) provided similar results, but did suggest positive effects of light therapy on depression response rates (‡50% reduction in IDS points) (26% more response; P = 0.031). Prespecified analysis showed effect moderation by baseline insulin sensitivity (P = 0.009) and use of glucose-lowering medication (P = 0.023). Light therapy did not affect depressive symptoms in participants with higher insulin sensitivity or those who use only oral glucose-lowering medication or none at all, but it did produce a relevant effect in participants with lower insulin sensitivity (212.9 IDS points [95% CI 221.6 to 24.2]; P = 0.017) and a trend toward effectiveness in those using insulin (212.2 IDS points [95% CI 221.3 to 23.1]; P = 0.094). Light therapy was well tolerated. CONCLUSIONS Although this trial is essentially inconclusive, secondary analyses indicate that light therapy might be a promising treatment for depression among a subgroup of highly insulin-resistant individuals with type 2 diabetes.

Original languageEnglish
Pages (from-to)529-538
Number of pages10
JournalDiabetes Care
Issue number4
Early online date11 Mar 2019
Publication statusPublished - Apr 2019


Acknowledgments. The authors thank Michaela Diamant (deceased), Professor of Diabetology at the VU University Medical Center, Amsterdam, the Netherlands; the research assistants; and the participants for their contributions to this study. Funding. This study was supported by a European Foundation for the Study of Diabetes (EFSD)/Lilly Mental Health award 2012. Duality of Interest. No potential conflicts of interest relevant to this article were reported. Author Contributions. A.B. performed statistical analyses, wrote the manuscript, set up and coordinated the trial, and performed study procedures. D.H.v.R. wrote the manuscript, designed and interpreted the diabetes-related outcome measures, and coordinated practical research assistance. H.-T.N. and A.C.M. wrote the manuscript, designed and interpreted the ophthalmological measures, and graded retinopathy. F.R. and P.J.M.E. wrote the manuscript, recruited participants, and coordinated practical research assistance. P.M.v.d.V. wrote the manuscript and designed statistical analyses. E.J.W.V.S. wrotethemanuscriptanddesignedandinterpreted the trial conditions and sleep measures. F.J.S. and A.T.F.B. conceived of the study, designed the study, interpreted the results, and wrote the manuscript. M.A.B. conceived of the study, set up the study design, supervised the coordination of the trial, wrote the manuscript, and is the principal investigator of this study. A.B. and M.A.B. are the guarantors of this work and, as such, had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Prior Presentation. This study was presented as a poster at the Society for Light Treatment and Biological Rhythms (SLTBR) 30th Annual Meeting, Groningen, the Netherlands, 21–24 June 2018; and was presented at Chronotherapie Netwerk Nederland (CNN) Annual Symposium, Amsterdam, the Netherlands, 18 May 2018.

FundersFunder number
Lilly Mental Health
Eli Lilly and Company
European Foundation for the Study of Diabetes
Vrije Universiteit Amsterdam


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