The theoretical foundation of CASBBI is based on the science of complex adaptive systems applied to a biopsychosocial model of disability. We envision that health and function in individuals with physical and mental disabilities is determined by the interactions between four adaptive systems (brain, sensorimotor, neuroimmune, and psychosocial influence mechanisms). External stressors and the corresponding adaptations of these systems lead to the allostatic load that contribute to illness and diminished quality of life. External modulations can reduce allostatic load and improve wellness.