I don't know if the vibrations specifically could have adverse effects, but I'd be worried about the toy breaking, ripping, or short-circuiting from being left on all night long and without someone consciously holding it and keeping an eye on it, especially if you toss and turn a whole lot (and for that matter, it might accidentally hurt you if the material's rigid enough).

Plus, you'll waste a lot of batteries (and wouldn't you rather save those for when you're awake enough to enjoy the vibrations?) and possibly shorten the life of the toy.

The only way I personally would sleep with a toy in me would be if it were a dildo (as in, non-vibrating) and made of soft silicone.

I don't know about the safety involved but personally I'd avoid it.

I wouldn't think it's the worst thing you could do, but toys can get really hot from being on and if it's inside of a warm area (the vagina); it's going to be even hotter. I would think, you could potentially get a burn from the motor overheating. I wouldn't recommend doing this. If you want to wear a toy, you should wear a non vibrating plug.

yuh i would worry about over heating... i would use non vibrating as well if you just had to have something in

Yeah, that's not a good idea. The smell of fried vagina/anus in the morning - yum!

Maybe someone needs to market one with a sleep timer? Works for televisions and radios.

Depending on the intensity and nature of the vibration, I could imagine some circulation and tissue problems with vibrating an area for too long. It's just like operating a jackhammer all day, or any other repetitive work injury. I would be worried about numbness and inflamation of any muscles or connective tissue in the area.

It doesn't sound like the best idea, but to each their own.

I've definitely napped with my lelo liv in my ass before. As long as the materials are safe, and your battery will last that long it is really nice to wake up feeling the vibrations. I find it quite a turn on!