An excess mortality for violence (suicide & injuries) has been observed following the use of cholesterol-lowering drugs. In this paper, a new hypothesis on the association among serum lipids, depression, & atherosclerosis is proposed. The hypothesis is based on epidemiologic evidence concerning these factors & on previous results concerning a cytokine, interleukin-2. Recent studies indicate that interleukin-2 has an important role in lipid metabolism, depression, & atherosclerosis. (25 refs.)