I think this is true, but only the vapid sense that absolutely everything in the body and mind is biochemical (and if you believe that the mind has non-biologic

I think this is true, but only the vapid sense that absolutely everything in the body and mind is biochemical (and if you believe that the mind has non-biological aspects then it ceases to be true). It's not necessarily likely that a single chemical is the cause (as is suggested in the serotonin hypothesis).