Mental Disorders and Medical Comorbidity

People with co-occurring physical and mental conditions represent a significant and costly portion of the population.

Health reform has increased attention on ways to improve quality and reduce the costs of health care. Expenditures and gaps in health care delivery are not evenly distributed across the population, however. To improve health care quality and reduce costs, policy-makers must focus on particular subgroups who are at greatest risk. Persons with mental health and medical comorbidities represent just such a population.

What is comorbidity, and what are the causes and impact?
Comorbidity is defined as the co-occurrence of mental and physical disorders within the same person, regardless of the chronological order in which they occurred or the causal pathway linking them. Having a mental disorder is a risk factor for developing a chronic condition, and having a chronic condition is a risk factor for developing a mental disorder. When mental and medical conditions co-occur, the combination is associated with elevated symptom burden, functional impairment, decreased length and quality of life, and increased health care costs.

The pathways causing comorbidity of mental and medical disorders are complex and bidirectional. Medical disorders may lead to mental disorders, mental conditions may place a person at risk for certain medical disorders, and mental and medical disorders may share risk factors. For instance, medical conditions that are accompanied by a high symptom burden, such as migraine headaches or back pain, can lead to depression. At the same time, major depression is a risk factor for developing chronic conditions, such as cardiovascular disease.


Exposure to adverse childhood experiences such as  trauma, abuse, and chronic stress are all associated with both mental and medical disorders, and responsible for much of the high rates of comorbidity, burden of illness, and premature death associated with chronic illness.


Managing and Treating Comorbidities
Models that integrate care to treat people with mental health and medical comorbidities have proven effective. Despite their effectiveness, however, these models are not in widespread use.

Many of the most common treatments for diseases may actually worsen the comorbid condition. For instance, many psychotropic medications can cause weight gain, a risk factor for type 2 diabetes. At the same time, many treatments for common medical conditions can have psychological side effects that may exacerbate or complicate underlying psychiatric conditions.


The most effective and cost-effective treatment for persons with comorbid mental and medical conditions involves a collaborative care approach that uses a multidisciplinary team to screen and track mental conditions in a primary care setting. In addition to the societal value, research has suggested that cost savings may be achievable over the long term, particularly among patients with the costliest and most complex conditions.

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