However this is a somewhat anti-intuitive treatment since SAD peaks in February and March when the Darkest Day is all the way back in December.
The current SAD theory has it that the hormonal balance regulated by the pineal gland causes disruptions in the normal circadian rhythms. Light therapy is thought to address this daylight deficit by supplementing artificial bright light which stimulates the production of melatonin. However numerous studies now contradict this premise.
The model I propose is more straightforward. It predicts a rising energy toward crescendo peaking around January 4th, followed by a rapid shifting of energy until springtime.
The current model insists that the seasonal shift in mood and health is primarily due to the length of daylight and the angle of the sun in the sky.
If this were true then winter-time depression would increase with higher latitudes. It does not. Also the winter depression rates in the Southern Hemisphere would mirror those of the North. They do not. They seem to conform to another (here-to-fore unexplained) seasonal pattern.
