Background: Previous studies have suggested that low plasma cholesterol levels or cholesterol lowering may increase the risk of suicide and violent death. Increased aggression, risk-taking behavior, or depression has been associated with low cholesterol levels in some studies. Methods: A total of 4240 subjects of the Coronary Artery Risk Development in Young Adults study, aged 23 to 35 years, were included in the study. Analyses were stratified by race (black or white) and sex. Persons in the lowest 10% of plasma total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglyceride levels were compared with the other participants in each race/sex group, using standardized measures of hostility, anger suppression, depressive symptoms, and anxiety. The relations between 5-year change in hostility and 5-year change in lipid levels also were examined. The relations between lipid levels and high-risk behavior (eg, violent arguments or having a gun at home) were examined in a subset of subjects. All analyses were adjusted for relevant covariates. Results: In cross-sectional analyses, low total cholesterol levels were not related to any of the psychological measures in any race/sex group. Among black women only, low low-density lipoprotein cholesterol was related to greater anxiety, and low triglycerides were related to lower anger suppression (P≤.002). Among white men only, increases in hostility during the 5-year follow-up were related to increases in triglycerides (P<.01), but changes in hostility were unrelated to changes in cholesterol levels. Among a subset of 371 subjects with initially elevated total cholesterol (≤5.17 mmol/L [≤200 mg/dL]) and a nonmedicated decrease of 0.52 mmol/L (≤20 mg/dL) or more during 5 years, hostility decreased in a univariate analysis (P<.001). High-risk behaviors also were not associated with low lipid levels. Conclusion: The results do not support a consistent relation between hostility, negative affect, or high-risk behaviors with low lipid levels or lipid-lowering among young adults.