A SAD lamp is a clinical dose of bright light for a diagnosed winter depression. Daily light is a pattern across the whole day. Why one cannot replace the other.

As autumn shortens the days and the clocks go back, the morning light that anchors the body clock fades. The mechanism, and what helps.

Most homes give the body a fraction of the daytime light its clock needs. The camping studies that reveal the gap, the window studies that show the cost, and how to close it.