Yes, it is highly likely biochemical. If you do not have enough of certain brain chemicals and/or if they do not fire correctly, then it causes these symptoms and disorders. These disorders can be genetic, too. Don't give up hope. You found one medication that worked and you will find another. Perhaps one day you can try Paxil again. It is frustrating when the drug that worked, one day stops working. I've experienced that a couple of times.