Bright light therapy for depression: A review of its effects on chronobiology and the autonomic nervous system

Abstract

Bright light therapy (BLT) is considered among the first-line treatments for seasonal affective disorder (SAD), yet a growing body of literature supports its use in other neuropsychiatric conditions including non-seasonal depression. Despite evidence of its antidepressant efficacy, clinical use of BLT remains highly variable internationally. In this article, we explore the autonomic effects of BLT and suggest that such effects may play a role in its antidepressant and chronotherapeutic properties. After providing a brief introduction on the clinical application of BLT, we review the chronobiological effects of BLT on depression and on the autonomic nervous system in depressed and non-depressed individuals with an emphasis on non-seasonal depression. Such a theory of autonomic modulation via BLT could serve to integrate aspects of recent work centered on alleviating allostatic load, the polyvagal theory, the neurovisceral integration model and emerging evidence on the roles of glutamate and gamma-hydroxybutyric acid (GABA).

• Autonomic nervous system
• bright light therapy
• chronotherapy
• major depressive disorder
• seasonal affective disorder
• sympathovagal balance

Notes

¹We use the term NS-MDD to identify all presentations of MDD exclusive of seasonal affective disorder (SAD). Per the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM 5), this includes all instances of MDD Single Episode and MDD Recurrent that do not meet criteria for the With Seasonal Pattern specifier.

²This author acknowledges the linguistic and practical inaccuracy of the term “prescribing” related to chronotherapeutics, particularly as no prescription is required. However, the words of Dilsaver (1989) remain timely over two decades later: “Light can be regarded both as a Zeitgeber and as a drug.” Furthermore, we are currently conducting such a survey to evaluate the attitudes of U.S. psychiatrists toward BLT.

³In this proposal, we appeal to the pioneer of the randomized clinical trial, A. B. Hill, who articulated criteria by which to assess causality. He cites “biological gradient,” “plausibility” and “coherence” as integral to establishing causation, each of which speaks to a biological premise upon which to base clinical judgment (Hill, 1965).

⁴Included search terms related to depression (depress*, emotion, mood and affective), BLT (bright light, light therapy, chronotherap*, phototherap*, color* and illuminat*) and ANS (autonomic, sympathetic, adren*, parasympathetic, sympathovagal, vagus, vagal, ganglion*, *cholin* and muscarinic).