This seems to be a piece of _pseudoscience_ commonly seen these days. The truth is that _this effect has never been statistically observed_.
From the Skeptics Stack Exchange site:
> Ivan Kelly, James Rotton and Roger Culver (1996) examined over 100 studies on lunar effects and concluded that the studies have failed to show a reliable and significant correlation (i.e., one not likely due to chance) between the full moon, or any other phase of the moon, and each of the following: The homicide rate, traffic accidents, crisis calls to police or fire stations, domestic violence, assassinations, kidnappings, aggression by professional hockey players, violence in prisons, assaults, gunshot wounds, stabbings
... and many more seen here.