I forgot to mention that after the extraction I started to take 600mg ibuprofen 3xday. I would have never thought that would affect mood but after looking for it on the internet there's plenty of evidence of it. I had taken ibuprofen in the past for other reasons, ranging from dental pain, hangovers, sprawn ankles, etc. But never noticed anything like this.
My new hypothesis : my brain was inflamed because of the root canal infection and the combination of ibuprofen+antibiotic+extraction is clearing the inflamation.