The treatment of depression is based on careful diagnostic evaluation. In the acute phase of treatment, brief psychotherapies (cognitive, interpersonal, psychodynamic or problem-solving) are effective in cases of mild to moderate depression. Antidepressants are also effective, their importance increasing alongside the level of severity. Electroconvulsive therapy (ECT) is effective for severe or psychotic depression. After the acute phase, antidepressants must be continued for at least six months to prevent a relapse; maintenance antidepressant treatment must be considered after three lifetime episodes. Primary health care is responsible for the majority of mild to moderate cases of depression, but psychiatric consultation services and nurse case managers are required to fulfill this task.