I lead EPQ in my school and whilst I am happy to give you some guidance, that is really the job of your supervisor.
I advise my students to research in a smart fashion: use Google Scholar rather than normal Google and if you have to start with Wikipedia, look at the references in the articles and go to them. Does your school/college have a subscription to JSTOR? When you find articles of interest, keep a hyperlink to them along with the date you accessed it, then summarise the main argument in a sentence or two. With your title, you will need to develop both sides of the argument as @Diospyros states so work out which side each article or research piece fits with. If you keep your notes for each side together, it will help with the writing up.
The EPQ I use suggests around 5000 words. I generally advise on 500 for the introduction and conclusion, then 1500 for each of the (normally 3) main points. So yours could be 1500 on trauma playing a part, 1500 on it not, and 1500 maybe on other childhood influences, or the like. Obviously tweak these, so if your argument is much stronger for the first, give yourself more words. I then suggest they write their opening paragraph for each point, more if they feel they can. When they know where they are going, I suggest they write their introduction. Use that to signpost your argument. Make sure your conclusion follows on from your essay: if you have loads of evidence of trauma being important, make sure your conclusion states it. Make sure you choose a referencing style and stick to it. Mine all use Word to type it up and it will do the referencing for you. Don't forget to keep saving your work!
Finally, you need to analyse your sources, ideally as you are going along. If you rely heavily on a disreputable source, you weaken your argument.
I would also ask someone other than your supervisor to read it once you have finished it. Lots of mine ask a parent or if it's on a subject that school staff know well, they ask them. It's always good to get another perspective.
Hope that helps. Feel free to tag me again if you need more advice.