Prediction of suicidal behavior from biologic tests

Biochemical studies related with suicidal behavior have mainly dealt with monoaminergic and corticosteroidal measures. We used some of these measures in a study of 61 suicide attempters who, except for occasional doses of benzodiazepines, had been medication free for a mean of 16 days. The monoamine metabolites 5-hydroxyindoleacetic acid, homovanillic acid, and 3-methoxy-4-hydroxyphenylglycol were measured in lumbar cerebrospinal fluid (CSF). We found that violent suicide attempters (N = 18) had 5-hydroxyindoleacetic acid concentrations below the median of all patients, whereas the concentrations of 3-methoxy-4-hydroxyphenylglycol were mainly above the median. We found no significant differences between violent and nonviolent (N = 43) attempters concerning CSF homovanillic acid, 24-hour urinary norepinephrine-epinephrine and cortisol, activity of monoamine oxidase in platelets, or post-dexamethasone plasma cortisol. Four patients completed suicide, and 3 of them had CSF 5-hydroxyindoleacetic acid concentrations at or below the median. All completed suicides had CSF 3-methoxy-4-hydroxyphenylglycol concentrations above the median. Urinary measures and platelet monoamine oxidase activity of completed suicides were in the higher concentration ranges. Patients who repeated suicidal behavior after the index investigation had low 24-hour urinary cortisol levels more often than those who did not repeat. Because our subgroups of patients are small, we cannot draw any firm conclusions about the value of our CSF and urinary biochemical findings predicting suicidal behavior. However, our CSF findings in violent suicide attempters are similar to those observed in other studies.