CNN  —  A headset worn at home that zaps the brain with the energy of a 9-volt battery could help relieve symptoms of depression, a new study shows. The study, which was published last week in the journal Nature Medicine, found that 87 adults with at least moderate depression who used the headset for 10 weeks had a greater improvement in their depression symptoms than 87 others who wore a similar-looking inactive headset over the same time period. What’s more, twice as many people in the group