Suicidal behavior is a major public health issue and there are currently no specific treatments for it. However, lithium, the reference treatment for bipolar disorder, have been shown to be effective in preventing suicidal risk. Apart from drug treatments, lithium is present in our environment and its levels varies from one individual to another, depending, especially, on diet. Knowing that patients with a mood disorder generally have a poor lifestyle and a less rich and varied diet than the general population, variations in basal lithium levels can be expected in these patients.