Very strong evidence now exists, including a mouse model of bipolar illness controlled by light exposure, that extending your photoperiod is the principle drive

Very strong evidence now exists, including a mouse model of bipolar illness controlled by light exposure, that extending your photoperiod is the principle driver of depression. You require total darkness (but red light is okay, see last line.) And rigid hours of darkness. Sleep is important for depression, but only affects the aldosterone cycle. If you sleep into the morning light, you're still killing your melatonin-controlled cycle. The pRGCs that control our clock were only discovered rather recently, so it will be perhaps a generation before you hear this from a front line doctor. pRGCs cannot detect red light.