Hypothesis: low serum cholesterol, suicide, and interleukin-2.

An excess mortality for violence (suicides and injuries) has been observed following the use of cholesterol-lowering drugs. It has been suggested that low cholesterol is associated with depression by modifying the serotonin metabolism. In this paper, a new hypothesis concerning the association among serum lipids, depression, and atherosclerosis is proposed. The hypothesis is based on epidemiologic evidence concerning serum lipids, depression, violent deaths, and atherosclerosis. It is also based on previous results concerning a cytokine, interleukin-2. Recent observations indicate that interleukin-2 has an important role in lipid metabolism, depression, and atherosclerosis.