Asberg and associaties found that about a third of 68 severely depressed patients at the Karolinska Hospital in Stockholm had low levels of 5HIAA, a metabolite of serotonin, in their CSF. Patients with low 5HIAA were twice as likely to commit suicide and lower levels lead to more violent suicides. 20% of people with low 5HIAA and a previous suicide attempt died from suicide within a year. Since depression underlies 65-80% of U.S. suicides, this finding is useful but not the complete solution.