Honestly I gained even more from the experience -- the suffering was for me a trial by fire. After the dust cleared I was able to gain a paradigm in life again. I am very well off now, compared to where I was while getting Invega-Sustenna out of my body, but even compared to my normal life before that.
I was diagnosed with brief PTSD and BPD (brief psychotic disorder) but it was well determined that I had no permanent mental defect. I had already graduated college by the time I had my 'episode' which led doctors to think Invega Sustenna was a good idea. What I frankly, really, needed was love. Just time, love, compassion, healing -- all these things were gratefully provided through my parents and others, especially a pastor and dear friend.
I can say that from the initial BPD and Invega injection, starting about a week or so after, I had serious depression -- yes, depersonalization. The way I phrased it was that I "lost my paradigm". I didn't have a basis of rational thought -- a foundation from which to build a worldview. It's like it left me when the drug altered my physical mechanism for thinking. I developed a very pessimistic, nihilistic, and almost atheist thoughtlife, and it haunted me for a long time.
All that said, yes, after 6 months it began to improve. The first 6 months were literally horrible, and I believe you when you say you have suffered and are suffering. For a time in the first couple months I had a strong uncontrollable impulse to get up, and pace/walk, as if to escape my body and thoughts.
After a full year I really was beginning to re-develop a sense of self and placement in existence. I read the scriptures (Bible) a lot more. Before the BPD I had read it entirely but Ecclesiastes in particular meant a lot to me in this time. My intelligence has been fully restored (if any were lost or altered in the first place). I'm firing on all cylinders. Eating well and a daily vitamin can only help you, even if the motivation is not there, you have to fight it. Do fight it. You can make it. I and others certainly have. I remember talking to a guy that said he suffered the same things from Invega but after 2 full years was totally back into a normal "swing of things".
What you (or anyone suffering from a temporary and especially unnecessary treatment with Invega Sustenna) need to know is this: You can and will get through this. I assure you that you may believe it is impossible, because so did I, but it is not impossible. The human body, mind and soul are absolutely glorious is their composition and capacity to heal.
Eat well, intentionally do good for yourself. Fight it. Pray. Pray desperately -- read scripture, do what you must, do what you can. Feel free to message back. I may not get around to responding immediately but I assure you I will make the effort eventually. As of now, I'm in graduate school working on a Ph.D. Nothing is impossible to him that believes, so do not lose faith in a full restoration.
If interested here's a thread I posted back in the thick of it:
http://www.bluelight.org/vb/threads/712455-Life-itself-bothers-me