Hi there! While I don't suffer from OCD, my guess is that because the short-term memory is temporarily diminished by marijuana, those recurring thoughts and stuff are being blocked or at least filtered since they exist in the short-term memory. I used to be a daily pot smoker but quit because of the cost and the will to become independent of drugs. I even used to do harder drugs like mushrooms and LSD and found myself having OCD-like symptoms while on these drugs, and from what I've gathered while under the influence of these drugs, the recurring thoughts exist in the short-term memory. I may be completely wrong though since I obviously do not have OCD, but it's something to think about. I hope this kinda helps answer your question! Take care.
