I'm in US and I know 2 people who have undergone voluntary ECT treatment. Both were in extreme bouts of year/+ long suicidal depressions. My bipolar friend who just had it done has been in the psych ward 4 times in the past 2 years. Once was in a psych med enraged blackout where the police had to escort her to the hospital. She finally was in patient for a month and with her pdoc made the decision for ECT. When we spoke she was a little concerned about things like why couldn't she drive right away or what was her bank balance etc. Her short term memory was affected. I asked her if she was depressed? No. Was she suicidal? No. How did she feel? I don't really know. Overall, it was an improvement from when she checked into the hospital. Carrie Fisher had it done and wrote about it in her book Shockoholic. It's a good book, and she has gone on to do many things since.

I don't think there's a big concern as I believe it's used as a last resort for extreme cases.