The norepinephrine-to-epinephrine ratio in patients with a history of suicide attempts.

Norepinephrine and epinephrine were measured serially in 24-hour urine collections from 99 male psychiatric inpatients with mixed diagnoses. The group was blindly divided into those with a previous history of at least one suicide attempt (N = 38) and those without such a history (N = 61). The ratio of norepinephrine-to-epinephrine levels was significantly lower in the group with a history of suicide attempts. The authors discuss the possibility that a low norepinephrine-to-epinephrine ratio is a risk factor for suicidal behavior.