Listen to me everyone.
I had major Depersonalisation and Derealization for about 3 years after smoking during my teenage years. I have always put it down to smoking cannabis. Basically it comes down to this. If you are prone to depression or inward thinking then this can happen regardless. Believe me when I say that it passes over time if you let it.
I honestly dont think you had real DP/DR based on what you say caused it. You may think that your experience seems to match the definition of DR/DP but as far as i know its caused by the complete lack of emotion and for that to happen you need to have fucked with your serotonin somehow. Im guessing DR/DP is open to interpretation and has probably been used to describe a number of different experiences, i just dont see how anything other then an issue with your serotonin can result in genuine DP/DR.