Suicide and lunar cycles: a critical review over 28 years.

20 studies which have examined the relations between completed suicide or attempted suicide and suicide threats with the synodic lunar cycle are reviewed. Most studies indicated no relation between lunar phase and the measures of suicide. The positive findings conflicted, have not been replicated, or were confounded with variables such as season, weekday, weather, or holidays. It is concluded that there is insufficient evidence for assuming a relationship between the synodic lunar cycle and completed or attempted suicide.