What is the most commonly used medical therapy for treating mood disorders that have not responded to medication?

Electroconvulsive therapy (ECT) is recognized as a highly effective treatment for severe mood disorders, particularly for those patients who have not responded adequately to traditional medications such as antidepressants. ECT is typically reserved for cases where other treatments fail, as it can bring rapid relief from symptoms of depression or bipolar disorder, particularly in situations involving severe depression or when there are safety concerns, such as suicidal ideation.

The effectiveness of ECT stems from its ability to produce changes in brain chemistry that can quickly alleviate symptoms. This is particularly critical for patients who are severely ill and may not have the time to wait for antidepressants to take effect, which can often take weeks. While other therapeutic options like psychotherapy or group therapy can be beneficial for mood disorders, they often serve as adjunct treatments rather than primary interventions in acute or treatment-resistant cases.