1. A method for providing an electrical neurostimulation therapy to a neural structure of a patient's body using an implantable medical device (IMD), comprising: providing a first electrical signal using said implantable medical device; applying said first electrical signal to said neural structure; providing an implanted sensor; sensing a physiological parameter using said implanted sensor, wherein said physiological parameter is selected from the group consisting of a neurotransmitter parameter, a neurotransmitter breakdown product parameter, a neuropeptide parameter, and a glucocorticoid (GC) parameter; modifying said first electrical signal based upon said sensed physiological parameter to generate a second electrical signal; and applying said second electrical signal to said neural structure.