Risk Factors in Treatment Placement

What is a dual diagnosis? Why is an integrated approach necessary for effective treatment with this population of individuals? Provide examples of an individual with a dual diagnosis. Provide a 400 word response to the questions. As appropriate, cite the online course, the textbook, and other credible, scholarly sources to substantiate the points you are making. 

I wanted to clarify the definition of dual diagnosis. I am attaching a short clip that further explains the concept. 

http://www.youtube.com/watch?v=OS6vk3jlb10