Comorbidity – Two Illnesses Occurring Together
Depression often co-exists with other illnesses, we call this comorbidity. Comorbidity is the rule with depressive and anxiety disorders. Co-morbid depression and anxiety is a common phenomenon. Such illnesses may precede the depression, cause it, and/or be a consequence of it. It is likely that the mechanics behind the intersection of depression and other illnesses differ for every person and situation. Regardless, these other co-occurring illnesses need to be diagnosed and treated. As a rule of thumb many psychiatrists assume comorbid depression and anxiety until proven otherwise. In other words; during an evaluation this relationship will be assumed, especially since it is often difficult for a patient to tell a doctor that they have two illnesses, all they know is they feel horrible. Identifying the primary and secondary illness is critical in assuring a positive prognosis. If the secondary illness is treated as the primary illness, often the symptoms will not dissipate, this is especially critical in treating comorbid ADHD and anxiety.
Anxiety disorders such as post traumatic stress disorder (PTSD), obsessive compulsive disorder, panic disorder, social phobia and generalized anxiety disorder, often accompany depression. People experiencing PTSD are especially prone to having comorbid depression. PTSD is a debilitating condition that can result after a person experiences a terrifying event or ordeal such as a violent assault, natural disaster, accident, terrorism or military combat.
People with PTSD often relive the traumatic event in flashbacks, memories, or nightmares. Other symptoms include irritability, hyper-vigilance, intense anger, and avoidance of thinking or talking about the traumatic ordeal. In a National Institute of Mental Health (NIMH) funded study, researchers found that more than 40 percent of people with PTSD also had depression at one-month and four-month intervals after the traumatic event.
Alcohol and other substance abuse or dependence may also co-occur with depression. In fact, research has indicated that the coexistence of mood disorders and substance abuse is pervasive among the U.S. population.
Depression and Anxiety Often Share a Comorbid Relationship with other Diseases
Depression also often coexists with other serious medical illnesses such as heart disease, stroke, cancer, HIV, diabetes, and Parkinson’s disease. Depression is implicated in both the development and adverse outcomes of heart disease. Biological pathways involving the sympathetic nervous system, the hypothalamic-pituitary axis, and the coagulation pathway are all implicated. Many often report severe depression after open heart surgery. Similar data seems to imply and demonstrate a link between anxiety, depression, and other common medical illnesses ranging from stroke and Parkinson disease to irritable bowel syndrome, cancer, and fibromyalgia. A recent study analyzing data from the US National Comorbidity Survey Part II concluded that anxiety disorders were positively associated with medical disorders after adjusting for depression, substance-use disorders, and socio-demographics. This conclusion indicates a strong and unique association between anxiety disorders and medical disorders. Indeed, the study noted a stronger association of anxiety disorders and chronic pain syndromes than the association of depression and chronic pain. Thus, depression, anxiety, and chronic medical illness are closely related. Again comorbid depression and anxiety are very common occurrences.
Separating the independent effect of depression and anxiety is difficult given their common concurrence. Studies have shown that people who have depression in addition to another serious medical illness tend to have more severe symptoms of both depression and the medical illness, more difficulty adapting to their medical condition, and more medical costs than those who do not have comorbid depression. Moreover, comorbid anxiety and depression may increase greater chances of non-response to treatment, long-term poor outcome, and suicide. Research has yielded increasing evidence that treating the depression can also help improve the outcome of treating the comorbid illness.