Why do suicide and crime rates go up on a full moon?

Opinions differ.

Some say that there's more crime during a full moon simply because there's more natural light those nights. Enough light to make it easier to sneak around, but not enough to be easily recognized.

There's good evidence for that, as a cloudy, overcast full moon night won't show any increase in crime, while a clear (moon) night will.

Others claim that it's the influence of the moon itself which causes it. Seems a little strange in that case, if cloud cover is all it takes to cancel it out.

There is more crime during the full moon because the lunar rhythm modulates human's sleep structure and influences secretion of melatonin and cortisol hormones.