New Trial Suggests Light Therapy may be a Promising Intervention for Treatment of Depression with Type 2 Diabetes

New Trial Suggests Light Therapy may be a Promising Intervention for Treatment of Depression with Type 2 Diabetes

By Aly Becraft, MS; Kevin C Maki, PhD

One in 11 adults have diabetes worldwide,1 with an estimated 25% of people with diabetes also suffering from depression.2 Co-occurrence of these diseases has been shown to increase risk for diabetes complications,3 potentially due to a lack of motivation to properly manage the disease.4,5 Therefore, people with diabetes and depression need effective therapies for both conditions in order to remain properly treated.

Often, depression simultaneously occurs with impaired sleep, leading to biological rhythm disturbances.6 While pharmacological interventions can be successful, some antidepressant drugs may have unfavorable effects on glycemic control in people with type 2 diabetes (T2D).7 Light therapy is an alternative or adjunctive treatment for depression with minimal side effects.8 It is thought to act by modifying the phase relationships between the biological clock and the light-dark cycle to restore appropriate sleep-wake cycles9 and has proven effective for treating seasonal depression (seasonal affective disorder) as well as some cases of non-seasonal depression.10-12 In 2017, an estimated 12% of global health expenditures were spent on diabetes,1 thus, if efficacy can demonstrated, light therapy would be a cost-effective treatment for T2D patients suffering from depression. In addition to altering mood states, sleep deficiency may also be related to changes in glucose metabolism and decreased insulin sensitivity.13 Previous studies have reported that partial sleep deprivation induced insulin resistance in healthy subjects and patients with type 1 diabetes.13-15 Therefore, the restoration of biological rhythmicity in individuals with impaired sleep may have the potential to improve glucose regulation.

Brouwer et al., (2019) report results from a randomized, double-blind, placebo-controlled trial which was published in Diabetes Care and investigated whether mood and insulin sensitivity could be improved via light therapy in clinically depressed patients with T2D.16 In this parallel-arm study, a total of 79 adults with depression and T2D were included in the outcome measures. Forty received light therapy (broad-spectrum, white-yellow light, 10,000 lux), while 39 received placebo therapy (monochromatic green light, 470 lux). Light therapy was provided in the homes of participants over 4 weeks for 30 minutes each morning. Participants were assessed for changes in depressive symptoms, and a subset of participants who agreed to hyperinsulinemic-euglycemic clamp (HEC) procedure were evaluated for insulin sensitivity. Both measures were assessed at baseline and after the 4-week intervention. Several secondary measures were also evaluated including anxiety symptoms, diabetes stress, self-reported insomnia, objective sleep duration, sleep efficiency, and mid-sleep time, as well as glycated hemoglobin (HbA1C) levels, fasting blood glucose, self-reported hypo-glycemic events and body weight.

After the intervention, light therapy did not significantly reduce depressive symptoms, and similarly, had no effect on insulin sensitivity in the primary analysis. However, per-protocol analyses were conducted to exclude 13 participants that changed glucose-lowering medication during the protocol, which resulted in 51 remaining participants.  In the per-protocol analysis, participants had a 26% greater reduction in depressive symptoms in response to light therapy (P=0.031). In addition, subgroup analysis suggested that patients with higher insulin resistance responded positively to light therapy (P=0.017), and there was a trend toward positive response in patients using insulin vs non-insulin glucose lowering medication (P=0.094). No significant differences in secondary measures were found between the treatment and placebo groups.

Comment.  Overall, the results of this study were inconclusive, but the per-protocol analysis was suggestive of improvements in depressive symptoms, which is a hypothesis-generating finding that should be investigated in additional research. Furthermore, the reduction in depressive symptoms observed in patients with higher insulin resistance may indicate greater efficacy of light therapy in this subset. A similar observation by Dimitrova et al., (2017) suggested that higher BMI, a factor strongly associated with insulin resistance, may be a baseline predictor for light therapy response in patients with seasonal depression.17 Although improvements in insulin sensitivity have been previously demonstrated in two case studies in response to light therapy,18,19 this effect was not established in the present study. This study shows potential for light therapy as a treatment for depression with T2D, but more research is needed with larger samples, longer duration of therapy and/or greater daily light exposure to more fully evaluate the effects of this therapy.



  1. Cho NH, Shaw JE, Karuranga S, et al. International Diabetes Federation (IDF) diabetes atlas: global estimates of diabetes prevalence for 2017 and projections for 2045. DiabetesRes Clin Pract. 2018;138:271-281.
  2. Goldney RD, Phillips PJ, Fisher LJ, Wilson DH. Diabetes, depression, and quality of life: a population study. Diabetes Care. 2004;27(5):1066-1070.
  3. Petrak F, Baumeister H, Skinner TC, et al. Depression and diabetes: treatment and health-care delivery. Lancet Diabetes Endocrinol. 2015;3:472-485.
  4. Gonzalez JS, Peyrot M, McCarl LA, et al. Depression and diabetes treatment nonadherence: a meta-analysis. Diabetes Care. 2008;31:2398-2403.
  5. Lin EH, Katon W, Von Korff M, et al. Relationship of depression and diabetes self-care, medication adherence, and preventive care. Diabetes Care. 2004;27:2154-2160.
  6. van Mill JG, Hoogendijk WJ, Vogelzangs N, et al. Insomnia and sleep duration in a large cohort of patients with major depressive disorder and anxiety disorders. J Clin Psychiatry. 2010;71:239-246.
  7. Deuschle M. Effects of antidepressants on glucose metabolism and diabetes mellitus type 2 in adults. Curr Opin Psychiatry. 2013;26:60-65.
  8. Wirz-Justice A, Benedetti F, Terman M. Chronotherapeutics for affective disorders: a clinician's manual for light and wake therapy, 2nd. Karger Medical and Scientific Publishers. 2013.
  9. Wirz-Justice A. Biological rhythm disturbances in mood disorders. Int Clin 2006;21:S11-5.
  10. Tuunainen A, Kripke DF, Endo T. Light therapy for non-seasonal depression. Cochrane Database Syst Rev. 2004;(2):CD004050.
  11. Perera S, Eisen R, Bhatt M, et al. Light therapy for non-seasonal depression: systematic review and meta-analysis. BJPsych Open. 2016;2:116-126.
  12. Mårtensson B, Pettersson A, Berglund L, Ekselius L. Bright white light therapy in depression: a critical review of the evidence. J Affect Disord. 2015;182:1-7.
  13. Spiegel K, Tasali E, Leproult R, Van Cauter E. Effects of poor and short sleep on glucose metabolism and obesity risk. Nat Rev Endocrinol. 2009;5(5):253.
  14. Donga E, van Dijk M, van Dijk JG, et al. A single night of partial sleep deprivation induces insulin resistance in multiple metabolic pathways in healthy subjects. J Clin Endocrinol Metab. 2010;95(6):2963-2968.
  15. Donga E, van Dijk M, van Dijk JG, et al. Partial sleep restriction decreases insulin sensitivity in type 1 diabetes. Diabetes Care. 2010;33:1573-1577.
  16. Brouwer A, Nguyen HT, Rutters F, et al. Effects of light therapy on mood and insulin sensitivity in patients with type 2 diabetes and depression: results from a randomized placebo-controlled trial. Diabetes Care. 2019.
  17. Dimitrova TD, Reeves GM, Snitker S, et al. Prediction of outcome of bright light treatment in patients with seasonal affective disorder: discarding the early response, confirming a higher atypical balance, and uncovering a higher body mass index at baseline as predictors of endpoint outcome. J Affect Disord. 2017;222: 126-132.
  18. Nieuwenhuis RF, Spooren PF, Tilanus JJ. Less need for insulin, a surprising effect of phototherapy in insulin-dependent diabetes mellitus. Tijdschr Psychiatr. 2009;51:693-697.
  19. Allen NH, Kerr D, Smythe PJ, et al. Insulin sensitivity after phototherapy for seasonal affective disorder. Lancet. 1992;339:1065-1066.



Photo by Duy Hoang