LED whitelights are fluorescent devices. And they are increasingly used for main lighting. Or nightlights!!!
Mostly they are Blue LEDs with fluorescent phosphors in the medium surrounding the pn junction. You can see they are whiter than tungsten bulbs. Tunsten has a smooth spectrum with very little at the blue end. Even warmlight LEDs have more blue in them than tungsten because the spectrum is a series of peaks. think RGB
In principle this is true of fluorescent (clue's in the name) lights including energy saving bulbs. And not that much less of a problem!
Blue light is present in daylight and enormously (more than that) present at mid-day. We evolved to be at our brightest then. Blue triggers the hormones mentioned (not those hormones AFAIK). Serotonin production is also implicated in the process, (hence Prozac et al).

The message is: only read by tungsten light in/before bed. I have a remote/dimmer on the main light so it has to be tungsten & I read the New Scientist to put me to sleep, and it does, and it has already carried an article about this & the warning.