Increased plasma nitric oxide level associated with suicide attempt in depressive patients

Background: Nitric oxide (NO) is known to influence cerebral monoaminergic activity, including the activity of serotonin. We evaluated plasma NO metabolite (NO_x) levels in depressive patients with and without a recent history of suicide attempt. Method: Plasma NO_x levels were measured in 39 depressive patients who had recently attempted suicide, 44 non-suicidal depressed patients, and 70 normal controls. The severity of depression was measured with the Hamilton's Depression Rating Scale. The lethality of the suicide attempt was scored using Weisman and Worden's risk-rescue rating scale and Lethality Suicide Attempt Rating Scale. Results: Plasma NO_x levels were significantly higher in suicidal depressive patients than non-suicidal depressive patients or normal control subjects (Z = - 2.472, p = 0.013). However, higher plasma NO_x levels in suicidal depressive patients were significantly related to a lower lethality of suicide attempts and lower severity of depression. Conclusions: Our study suggests that increased plasma NO_x level is associated with suicide attempts in depressive patients. Moreover, higher plasma NO_x level is related with suicide attempts in mild depressed patients. However, further studies are required to understand the role of NO system in depression and suicidal behavior.