Asking about suicide does not increase the risk of suicide. Those with suicidal plans should be hospitalized immediately. Sometimes a definitive diagnosis cannot be made on the basis of history and examination alone. Such situations are common when demented patients stop eating or deteriorate in another way that suggests depression. A trial of treatment, usually with an antidepressant, is the best course for these patients.
Laboratory tests have an adjunctive role in the evaluation of depressed patients.
However, thyroid function should be assessed for all new cases. A slightly low thyroxine level and an elevated thyroid-stimulating hormone level are common during a depressive episode. Most other tests should be ordered only when clinical findings suggest a concurrent disorder. An ECG can provide a baseline if concerns arise about the effect of tricyclic antidepressants on cardiac function. Although not diagnostic, the dexamethasone suppression test may help predict prognosis.