Light, via the photoreceptor melanopsin, may exert its antidepressant effect through a modulation of the homeostatic process of sleep. This statement is:

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Light signals through melanopsin-containing cells in the retina help regulate mood by tuning the sleep–wake system. These intrinsically photosensitive retinal ganglion cells respond to ambient light and project to brain areas that control circadian timing and sleep homeostasis. By supporting proper circadian alignment and modulating the homeostatic sleep drive (Process S), light exposure—especially bright daytime light—can improve sleep quality and daytime alertness, which in turn can elevate mood and produce antidepressant effects. Clinical evidence showing that light therapy improves depressive symptoms often accompanies improvements in sleep patterns and circadian timing, indicating that mood benefits can arise from changes in the homeostatic sleep process mediated by melanopsin signaling. While circadian realignment is a major contributor, the link via sleep homeostasis is a plausible and supported mechanism, making the statement true.