Comorbidity is the condition when one or more additional conditions co-occur with the primary illness. The branch of medical science describes the effect that the coordinating conditions have on the illness affecting a person. It could be physical like flu, cough and body ache accompanying a fever or mental illness such as depression and anxiety that co-exist together. The conditions of comorbidity can co-exist with each other or exist independently. Sometimes the co-existence of such conditions when overlap with each other creates complications which can become fatal for the patient whereas in other cases they could be utilized as symptoms to recognize the disease.