After seeing many claims on the internet about 6500K triphosphor fluorescent lamps being able to combat seasonal affective disorder or SAD. I wonder if such fluorescent lamps actually do the job of treating SAD. If so, I would like to know how such fluorescent lamps help combat SAD.

It needs to provide sufficient illumination intensity to work (comparable with a real daylight outside, maybe just under a shading roof or so). In fact the intensity is more important, the color is for that to only not look weir (even 4000K looks very creepy yellow at these intensities).
Otherwise just using 6500K 11W CFL for a big room won't work. Not because of the 6500K CFL, but because being just barely 700lm.

And generally more important is to follow the day cycle and to get a good rest at night. Without any light,...