Relation of serum cholesterol, lipid, serotonin and tryptophan levels to severity of depression and to suicide attempts.

OBJECTIVE To determine if there is a relation to low serum cholesterol, lipoprotein, serotonin or tryptophan levels in patients with depression who have recently attempted suicide. DESIGN Biochemical and behavioural study. SETTING Inpatient and outpatient treatment at the Instituto Mexicano de Psiquiatría. PARTICIPANTS Thirty-three patients with a diagnosis of major depressive episode. Eighteen of these patients had attempted suicide in the month before the start of the study; 15 patients had never attempted suicide. OUTCOME MEASURES Serum levels of total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides, serotonin (5-HT) and tryptophan. Scores on Hamilton Depression Rating Scale, Carroll Depression Rating Scale, Beck Hopelessness Scale and Beck Suicide Attempt Severity Scale. RESULTS There were no significant differences between patients who had attempted suicide and those who had not in terms of serum cholesterol, HDL, LDL and triglyceride levels. Serum levels of 5-HT and tryptophan were significantly lower in patients with depression who had a recent suicide attempt than in those patients who had never attempted suicide. A comparison of patients not taking antidepressant medication found serum 5-HT levels to be more than 3 times lower in those patients with a recent suicide attempt than in patients with no history of suicide attempt. CONCLUSIONS The study found no difference in lipid profiles between patients who had attempted suicide and those who had not. Low serum levels of 5-HT may increase the risk of suicide attempt in patients who are depressed.