You brought up an important factor: most (if not all-?) SAD lights, even 'blue lights', are run on a fluctuating, fluorescent current.
This source is a unnatural, neurological irritant; interupting nerve transmissions, that interfer with optic and brain functioning, sometimes causing migraines or seizures.
I get migraines from fluorescent lights, if they are too close, and too bright. In fact, to avoid migraines at work, with combined irritants of the computer screen and fluorescent lights, I need to wear those big polarized (cuts glare) sunglasses (fit over regular glasses) that block light from tops and sides (like mountain climbing glasses), to be free of these debilitating headaches.
I relate to the trigger aspect of fluorescent lights, too. They are not in my home, for this reason.
I'm all for walking in winter; when bundled up, I love the cold air, the interesting view of bare branches upon the sky, and the brisk wind upon my face.
Helpful thoughts! There are healthier ways.