In today’s Straight Dope Classic, Cecil effectively debunked the tidal effects theory of lunacy. Also, he quoted studies which found no discernable links between the full moon and crime or psychoses.
Still, if this is an urban legend, it is one that pre-dates the term by many centuries. With that sort of longevity it seems reasonable that there must be some sort of basis for it.
The one thing I have never seen mentioned in discussions of full moon fever is the fact that the nights are a lot brighter during a full moon. This fact may have escaped you if you have always lived in an urban area, but it is glaringly (heh) apparent to rural dwellers. On a clear night, the full moon can be bright enough to activate the cones in your eyes so that colors are apparent. This extra period of light must have some effect on humans and other diurnal species.
Does anyone know if there have been any studies into this aspect of the full moon and its physiological effects? Maybe a change in serotonin levels or a greater incidence of insomnia or night terrors? Please enlighten me.