CHICAGO: Stimulating the brain with rapid bursts of magnetic energy is a safe and effectively treatment for major depression, a new large-scale study has found.

The finding offers a ray of hope to the 20 to 40% of patients who do not respond to antidepressants and psychotherapy and to those who do not wish to treat their illness with drugs.

"This study provides new support for the efficacy of TMS (transcranial magnetic stimulation) as a 'stand alone' treatment for depression," said John Krystal, editor of 'Biological Psychiatry' which will publish the study on December 1.

"This finding could be particularly important for patients who do not tolerate antidepressant medications, for whom they are not safe, or who have not benefited from other alternative treatments."

It works by sending very rapid bursts of magnetic energy into the brain through coils attached to the scalp. These pulses cause the neurons in a small area of the brain to "fire off", said study co-author Philip Janicak, a psychiatry professor at Rush University Medical Centre in Chicago.

"It also indirectly sends signals down to the deeper areas of the brain which controls the appetite and are linked to depression," he said.