Some say that it does cause initial shedding, that stops after 2-3 months.
Presonally I believe that laser helmets do work, but not as a main weapon, only as a secondary.
It can slow down your loss, make your hair look better and even regrow some hairs, but nothing to get too excited about.
As the guy above you stated, don't get near the combs, when you move the laser every second to another point on your scalp it's useless, you need some hat/helmet that sits on your head for 30 minutes and gets the job done.