Let's see if I can help you!
So, let me first begin by saying I'm not an EE expert and these are just my opinions and observations having done an EE myself (English though I'm afraid), had friends do their EEs in Psychology and studying the subject at HL myself.
From a quick glance, it seems your original question was a little bit too specific, hence why you probably found it hard to find information
Your new area of study, however, has a lovely amount of information on it, most of which is covered in some of the IB units for psychology.
With the childhood aggression topic, I can see two possible routes you can go down. The first one being the one you briefly mentioned about genetics. The Question: To what extent is childhood aggression biologically based?
With this essay you would start of by making your argument (that childhood aggression is due to genetics). For the remainder of the essay, you would examine the sociocultural and cognitive aetiologies (posh word for 'origins', minus the 'a' if you are american
). Pay attention to the works of Bandura for your social explanation! At the end of the essay, you will draw a conclusion based on the research you have found and discussed.
The other route you could take is looking at the effects of childhood aggression on a persons life. The Question: In what ways does aggression in an individual's childhood affect their development?
This is a very developmental question but, from a personal perspective, it is more original than the previous one. Anyway, my experience in this area is limited but research might be out there. You were considering doing a similar question originally but didn't have enough for a whole essay as I understand it so this might be a good question to do.
Before you make any decision, look through the EE help online. Look at the actual EE marking criteria as it has a break down on how you're assessed in each area for each subject. Finally, ask your supervisor before you settle on a final question.
Hope this helps