I wouldn't go with the cold hard truth. As bad as this may sound, find a story that is believable and commit to it. The first time I had a lengthy gap in employment due to my illness also happened to coincide with a time when my grandmother's health had taken a significant downward spiral. I hadn't really planned a response to questions about my lapse in employment when I was interviewing and the first time someone asked me I just spun a lie on the spot and said that I had taken time away from working to help my family care for my grandmother who was ill. They accepted it, didn't ask more questions and didn't scrutinize my lapse in employment any further, instead focusing on my education and experience. It seemed to work so I stuck with the same story with subsequent potential employers. I think I only had two or three different interviews before I landed a great position.
The next lapse of employment for me was much, much longer but I also happened to have my daughter during that time. So when returning to work and people asked about the lapse I said it was because I had been a stay-at-home-mom. Sure that was the truth, but my lapse in employment began well before I became a mother, but nobody was checking birth certificates and verifying dates. Taking time off to be a mother was acceptable in an employer's view and they didn't ask further questions about the lapse...they focused on what I could bring to the job. I got the second job that I interviewed for.
Both times I wasn't really truthful but there was a thread of truth to what I was saying which helped me to just stick to the story. If you tell a potential employer that you haven't been working because you are a trauma survivor, as unfair as it seems, you won't be getting a call back from them. I know there will be some people who will not agree with what I did, but this is what has worked for me.