Hi and thanks for the question.
I'll work on your answer and get back to you as soon as I can.
The biopsychosocial model is a more modern interpretation of a very old understanding, that the mind and body are one. (Prior to the Greeks, most psychological historians agree that unified mind and body thinking was the norm. The Greek culture was the first major culture to separate mind, body and spirit.) George L Engel is considered the founder of the modern interpretation of this school of thinking. His work on this concept in the late 1970’s struck the basic premise that certain experiences go far beyond the simple biological. For example, a patient has frequent headaches, anxiety and worry. The biological model would look at muscle reaction to the sympathetic nervous system; cortisol and adrenal production, and the lack of rest and sleep that contribute to anxiety when these adrenaline and cortisol levels spike. However, the biosocial model, which is extremely useful in clinical psychology because it is so applicable to treatment, seeks to add a social human factor into the problem and to look at psychology and biology in an integrated manner. So when someone complains of anxiety and headaches and worry, medical interventions such as SSRI’s; cortisol inhibitors and similar could be used to assist the body to cope with the symptoms. That is the biological approach. The biopsychosocial model goes a step further, looking into negative thinking, self-destructive patterns, learned pattern from family as another avenue for treatment. Essentially the approach allows the best of both worlds and integrates treatment at a physical and emotional, behavioral level. Simply, it is becoming the best practice approach to most disorders in clinical psychology.
I hope this helps,