Well there's the magnetic version with no electrical contact with the head:
https://en.wikipedia.org/wiki/Transcranial_magnetic_stimulation
And the electrode version:
https://en.wikipedia.org/wiki/Cranial_Electrotherapy_Stimulation
Honestly, while the principle is potentially useful, it seems completely implausbile that just applying a simple current waveform is going to make a person happy, "fix" them, or do anything constructive. If there was feedback to look for a particular response in a particular part of the brain and the applied stimulation tries to promote or retard that reaction, it's more believable.
With some of these, it's difficult to get a true double blind test and placebo effect is so very strong. I mean, how could people not notice the difference between "shocking" and "not shocking" somebody's head? And say you have a procedure that for sure makes your fingertips tingle and nothing else. I could tell people it's a cure for depression, neuralgia, etc and those who feel the tingle all go crazy that it's doing something. Not really a double blind test at all.
Well, there were reports that it caused some weird trippyness that seemed similar to some people's "alien abduction" experiences. That did get me curious. I also heard other people reported feeling nothing which does suggest more of a placebo effect.
Electroshock therapy (electroconvulsive therapy, ECT) is completely different. It is not banned either, but it has substantially changed form. It used to be pretty high current, done while awake, and used VERY indiscriminately. Nowadays, very uncommon, done while asleep as far as I know. It's viewed as a "last resort" treatment and is commonly considered very controversial. I think it was also capable of shaking up a person's brain but the positive results were likely placebo responses. I mean if I physically shake you until you're punch-drunk, how likely is this to cure your depression?