I had ECT, finishing about a year ago, for depressive phase of bipolar II. I had about 34 treatments over 3 months and it didn't work for me. I reckon I have lost about 18 months- 2 years of memory, basically the treatment period and about 18 months retrospective of that. Despite not having a positive outcome, I have no regrets because I know now that it is not a treatment option for me going forwards, and I'm not left wandering 'what if'. ECT works for more people than it doesn't, and for me, potentially losing memories was a small price to pay for some relief of symptoms.
I had unilateral, bifrontal and bilateral (in that order) and found the bilateral by far the worst in terms of side effects. I think if it had worked and I had stopped after unilateral like many people do, the effects would not have been so severe.
During the treatment, I had real trouble forming new memories. I would forget someone had visited me and have the exact same conversation when they visited me the next day, or read the same chapter of a book every night because I couldn't remember reading it the night before. It was like each treatment (every 2-3 days) kind of reset my short term memory. I can't really remember anything from the treatment, just the odd snippet of memory.
Immediately after the treatment, I found things like unpacking the dishwasher hard because I couldn't remember where things went, or I couldn't remember where friends lived and had to check a map, but those sort of memories returned pretty quickly.
Now that some time has passed, the worst thing is realising I've forgotten a whole holiday, or decisions that I made but don't remember making, or the rationale behind them, or complimenting someone on a bag, only for them to say that I gave it to them a few years ago. It can also be distressing to hear my family/ friends talk about that time and how they coped, because I have no memory of it or anything they were doing to support me. I have also forgotten a lot of the day-to-day memories that aren't important in themselves, but were important in certain relationships. I haven't lost friends over it, but someone times it makes me sad or anxious to know that their perception of the relationship is different to mine. However a positive is I've forgotten a really bad period of my ilness.
It's kind of like having too much to drink one night and waking up the next morning. You have snippets of memory and sometimes someone filling in a detail can jog a memory, but most of it is gone.
In terms of long term side effects, I don't think I have experienced any. I am pretty sure that my cognitive abilities have completely recovered although it is hard to know for sure. I feel like I am leading a completely normal life now (apart from the bipolar of course), just with some holes in my memory. Another positive outcome of the ECT was that it confirmed my diagnosis to my psychiatrist, and she was able to put me on a drug that has actually worked (for now).
While the notion of losing memories can be terrifying, I personally found it to be worth the risk for a potential effective treatment.