Impact of blue vs red light on retinal response of patients with seasonal affective disorder and healthy controls Anne-Marie Gagné a, ⁎, Frédéric Lévesque b , Philippe Gagné c , Marc Hébert a a Research Center University Laval Robert-Giffard (F-4500), Québec, Canada b Civil Department of Sherbrooke University, Sherbooke, Canada c Optic, Photonic and Laser Research Centre, University Laval, Québec, Canada abstract article info Article history: Received 6 April 2010 Received in revised form 29 October 2010 Accepted 10 November 2010 Available online 20 November 2010 Keywords: Blue light hazard Electroretinogram Light therapy Seasonal affective disorder Objectives: Seasonal affective disorder (SAD) is characterized by a mood lowering in autumn and/or winter followed by spontaneous remission in spring or summer. Bright light (BL) is recognized as the treatment of choice for individuals affected with this disease. It was speculated that BL acts on photosensitive retinal ganglion cells, particularly sensitive to blue light, which led to the emergence of apparatus enriched with blue light. However, blue light is more at risk to cause retinal damage. In addition, we reported using electroretinography (ERG) that a 60 min exposure of BL could reduce rod sensitivity. The goal of the present study was to verify if this decreased in sensitivity could be a consequence of the blue light portion present in the white light therapy lamps. We also wanted to assess the effect of monochromatic blue light vs red light in both healthy controls and patients with SAD. Method: 10 healthy subjects and 10 patients with SAD were exposed in a random order for 60 min to two different light colors (red or blue) separated by an interval of at least 1 day. Cone and rod ERG luminance- response function was assessed after light exposure. Results: A two-way ANOVA indicates that blue light decreases the maximal ERG response (Vmax) in both groups in photopic (p b 0.05) and scotopic conditions (p b 0.01). Conclusion: The main finding of this experiment is that blue light reduces photoreceptor responses after only a single administration. This brings important concerns with regard to blue-enriched light therapy lamps used to treat SAD symptoms and other disorders. © 2010 Elsevier Inc. All rights reserved. 1. Introduction Seasonal affective disorder (SAD) is a syndrome characterized by a mood lowering in autumn and/or winter followed by a spontaneous remission in spring or summer (Rosenthal et al., 1984). In the DSM-IV, SAD is classified as a subset of recurrent major depression with seasonal pattern (DSM-IVR). But in contrast to typical symptoms of decreased appetite and insomnia usually observed in major depres- sion, SAD patients tend to demonstrate more atypical symptoms such as hyperphagia and hypersomnia (Partonen and Rosenthal, 2001). The origin of SAD remains unknown, although it is recognized that the mood and symptom fluctuations seem to be linked to seasonal change in the photoperiod. In fact, the decrease in light exposure during fall and winter has been hypothesized to trigger SAD whereas the increase of light exposure during spring and summer was hypothe- sized to prompt the remission. Consequently, administration of bright light (BL) was proposed and recognized as the treatment of choice for individuals affected with SAD based on well documented therapeutic efficacy (Eastman et al., 1998; Golden et al., 2005; Lam et al., 1997; Terman et al., 1998). Currently, the recommendation for bright light therapy consists in a daily exposure to an artificial white light source of 10,000 lx for about half an hour, preferably in the morning (DBT, 2009). This particular treatment has been shown to be as effective as antidepressants to alleviate depressive symptoms (Partonen and Lonnqvist, 1996) with the advantage of avoiding medication. The way BL acts to alleviate SAD symptoms is unknown. But the discovery of a third class of photoreceptor called «intrinsically photosensitive retinal ganglion cells» (ipRGC) has generated a new knowledge about circadian physiology which may have some implication in our understanding of some circadian disorders and their treatments, such as light therapy in SAD (Terman, 2009). Indeed, ipRGC contain melanopsin, a photopigment that is highly sensitive to blue wavelengths (Gamlin et al., 2007). Moreover, this system appears to be specialized in ambient light irradiance measurement and non-image forming photoreception (Bailes and Lucas, 2010). The discovery of melanopsin has triggered considerable interest in blue Progress in Neuro-Psychopharmacology & Biological Psychiatry 35 (2011) 227–231 Abbreviations: BL, bright light; ERG, electroretinogram; SAD, seasonal affective disorder. ⁎ Corresponding author. E-mail address: anne-marie.gagne@crulrg.ulaval.ca (A.-M. Gagné). 0278-5846/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2010.11.009 Contents lists available at ScienceDirect Progress in Neuro-Psychopharmacology & Biological Psychiatry journal homepage: www.elsevier.com/locate/pnp