The effect of sunlight exposure on interleukin-6 levels in depressive and non-depressive subjects

Abstract

BackgroundThe objective of this epidemiological study was to evaluate the effect of length of sunlight exposure on interleukin 6 (IL-6) levels in depressive and non-depressive subjects.MethodsThis was a cross-sectional study with 154 subjects (54 males, mean age: 43.5 ± 12.8 years) who were living in a rural area in south Brazil. Chronobiological and light parameters were assessed using the Munich Chronotype Questionnaire. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index. Depressive symptoms were assessed with the Beck Depression Inventory. Plasma levels of inflammatory cytokines (IL-2, IL-4, IL-6, IL-10, tumor necrosis factor-α, and interferon) were collected during the daytime and measured.ResultsIL-6 levels showed a positive correlation with light exposure (r = 0.257; p < 0.001) and a negative correlation with the mid-sleep phase on work-free days (r = -0.177; p = 0.028). Multiple linear regression analysis showed that only the length of light exposure was an independent factor for predicting IL-6 levels (ß = 0.26; p = 0.002). In non-depressed subjects, exposure to a different intensity of light did not affect IL-6 levels (t = -1.6; p = 0.1). However, when the two depressive groups with low and high light exposure were compared, the low light exposure group had lower levels of IL-6 compared with the high light exposure group (t = -2.19 and p = 0.0037).ConclusionsThe amount of time that participants are exposed to sunlight is directly related to their IL-6 levels. Additionally, depressed subjects differ in their IL-6 levels if they are exposed to light for differing amounts of time.

Role of Interleukin-6 in Depressive Disorder

“…Levels of IL-6 were lower in the low light exposure depressive group compared to the high light exposure to depressive groups. The hypothesis that impairment of the suprachiasmatic nucleus leads to different IL-6 levels in the depressive subjects was established in this study, and that MDD could benefit from sunlight exposure [122].…”

“…A direct relationship between sunlight exposure and plasma IL-6 level changes in a study where the effects of sunlight exposure on plasma IL-6 in depressive and non-depressive subjects were investigated [122]. IL-6 levels were not affected by exposure to various different intensities of light in non-depressed subjects.…”

Psychiatric hospitalizations for affective disorders in Warsaw, Poland: Effect of season and intensity of sunlight

“…For instance, Tsai et al (2011) observed sunlight-related variation of striatal dopamine receptor availability. Other limited data reported seasonal variations in serum BDNF concentrations (Molendijk et al, 2012) or changes in interleukin-6 levels depending on the sunlight exposure (Levandovski et al, 2013). Finally, it should be mentioned the role of vitamin D in depression (Howland, 2011).…”

Light-harvesting chlorophyll pigments enable mammalian mitochondria to capture photonic energy and produce ATP

“…Both increased sun exposure (Dhar and Lambert, 2013;John et al, 2004;Kent et al, 2013a;Kent et al, 2013b;Levandovski et al, 2013) and the consumption of green vegetables (Block et al, 1992;Ferruzzi and Blakeslee, 2007;van't Veer et al, 2000) are correlated with better overall health outcomes in a variety of diseases of aging. These benefits are commonly attributed to an increase in vitamin D from sunlight exposure and consumption of antioxidants from green vegetables.…”