Most investigations of "antidepressant" medications have depended on clinical assessment of the symptom. This study undertook to apply an objective measure of depression to determine the effectiveness of nialamide, as representative of monoamine oxidase inhibitors, in a state hospital population.The results showed that both ward behaviour and depression improved significantly more in a high dosage group than for the low dosage and control groups but at the risk of additional behavioral and physical side effects. It was concluded that the measure of depression employed has merit and that nialamide used watchfully in high doses represents a worthwhile contribution for the treatment of the depressed or apathetic patient.Abstract Teaser