Addendum 11/15/06: Fair is fair. I found an even better review by one Eric Chudler, PhD at Univ. of Washington, called Neuroscience for Kids. (don't laugh). I didn't review all the links, but it is certainly more comprehensive than what I have here.
You know how everyone says that people go insane when there's a full moon? Well, I looked it up.
Most studies finding a link vbetween violence and the moon were done in the 1970s. For example, a 1978 study found a lunar relationhsip to everything-- suicides, asssaults, MVAs, and psych ER presentations, with both homicides and assaults both occurring more often around the full moon. Then again, you have to be suspicious of any study that actually tells you they actually used a computer.
But by the 1990s, this lunar relationship was on the way out. Consider a 1997 study in Italy found no relationship between community psych contacts and the moon phases. A 1998 Australian study found no relationship between violent episodes in inpatient psychiatric patients and the moon phases. A Spanish 2002 study found no link between ER presentations for violence and the moon's luminosity. A German 2005 study found only the weakest link between completed suicide and the moon (the new moon, mostly.) A 1992 Canadian study reviewed 20 studies covering 30 years and found no link to attempts or completed suicides and lunar phases. And, to prove a point, a gigantic Austrian study in 2003 found no relationship between lunar parameters (phases or sideric) and any ER presentations.
Which brings me to one point-- do Americans do anything other than drug studies? Well, one non-clinical study was done in Texas and found no link between prisoner violence and lunar phases.
So it is with violence and suicide. But what about other behaviors? I haven't had time to investigate the question, but two studies are suggestive. One (British) 2000 study found a slight increase in presentation to family practice clinics during full moons that was not due to psychiatric symptoms. An Austrian 2003 study found a strong relationship between thyroid clinic appointments and dates around the full moon. And a strange (British) 2003 study finding that women called a crisis center more frequently on the new moon.
I did find an interesting (Greek) study finding an excess of seizures on full moons (34% vs. about 21% for the other phases.) Importantly (and in contrast to suggestions by other studies) these were not pseudoseizures, because all patients were monitored. The authors speculate either electromagnetic/gravitational effects (hey, it could happen) or an interaction between the intrinsic seizure threshold and the environment (i.e. you can change your own threshold.)
My interpretation of this is that the moon can't affect your behavior directly (duh), but one's relationship to lunar cycles could influence your behavior. Take the classic wolf and full moon relationship. Prey animals, such as rats, generally reduce their activity during the full moon (don't want to get caught, I guess.) Wild maned wolves (which eat rats) travelled significantly less during the full moon. The authors' explanation was that prey is less available, so wolves would want to conserve energy. Additionally, maybe one reason why so few studies are American is that we have a lot of artificial night light, so the moon has less or no influence, while elsewhere there is less artificial light? Who knows. I'm going to bed.