Although several meta-analyses have shown anti-suicidal properties of lithium in treating patients with mood disorders, these effects may be unrelated to the mood-stabilizing effects. Some epidemiological studies suggest that even very low lithium levels induced by routine consumption of lithium from tap water may have anti-suicidal effects both in patients with mood disorders and in the general population. We hypothesize that even very low but sustained lithium intake can prevent suicide in the general population. If this is the case, increasing lithium levels of drinking water could potentially reduce the risk of suicide, and justify administering lithium to tap water.