Effects of Light Therapy on Mood and Insulin Sensitivity in Patients With Type 2 Diabetes and Depression: Results From a Randomized Placebo-Controlled Trial

Feb 24, 2019Diabetes care

Light Therapy and Its Impact on Mood and Insulin Sensitivity in People with Type 2 Diabetes and Depression

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Abstract

Light therapy did not significantly reduce depressive symptoms or improve insulin sensitivity in patients with type 2 diabetes.

No significant difference was observed between light therapy and placebo in reducing depressive symptoms, with a change of -3.9 IDS points.
Light therapy had no effect on insulin sensitivity, showing a change of 0.15 mg/kg*min.
Adherence to the light therapy protocol suggested a 26% higher response rate in depressive symptoms among participants.
Participants with lower insulin sensitivity experienced a significant reduction in depressive symptoms of -12.9 IDS points.
Light therapy showed a trend toward effectiveness in participants using insulin, with a reduction of -12.2 IDS points.
The treatment was well tolerated among participants.

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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 (-3.9 IDS points [95% CI -9.0 to 1.2];= 0.248) and had no effect on insulin sensitivity (0.15 mg/kg*min [95% CI -0.41 to 0.70];= 0.608). Analyses incorporating only those participants who accurately adhered to the light therapy protocol (= 51) provided similar results, but did suggest positive effects of light therapy on depression response rates (≥50% reduction in IDS points) (26% more response;= 0.031). Prespecified analysis showed effect moderation by baseline insulin sensitivity (= 0.009) and use of glucose-lowering medication (= 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 (-12.9 IDS points [95% CI -21.6 to -4.2];= 0.017) and a trend toward effectiveness in those using insulin (-12.2 IDS points [95% CI -21.3 to -3.1];= 0.094). Light therapy was well tolerated. P P n P P P P P

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.

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Effects of Light Therapy on Mood and Insulin Sensitivity in Patients With Type 2 Diabetes and Depression: Results From a Randomized Placebo-Controlled Trial

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