When my mother was still alive, she was seriously considering ECT because her depression was so bad and ADs never worked on her for very long (which led her to drink, which probably caused her death - I think she needed a mood stabilizer).

When we were looking into it together, we learned that it's MUCH safer and saner than it used to be, and MUCH more targeted, but they still don't fully understand why/how it works... the basic theory is that it "resets" the brain... my mom was not willing or able to take mushrooms (she also dealt with psychosis, another reason I always thought she needed a mood stabilizer), so ECT was looking better than the path she ended up taking, which was just drinking heavily because in her words, "ADs are futile". It didn't help any that our entire family is completely against modern medicine and kept telling her medications are "poison" and she should be off them.