What Is Comorbidity?

When a Person Has More Than One Condition

When a person has two or more health conditions at the same time, or if one condition occurs right after the other, this is known as comorbidity. Conditions described as comorbidities are often chronic (long-term) conditions such as diabetes and high blood pressure.

Other names for comorbid conditions include co-occurring conditions, coexisting conditions, and less commonly, multiple chronic conditions or multimorbidity.

This article provides examples of common comorbidities, what causes them, and how they are treated.

Mental health and substance abuse support group
SolStock / E+ / Getty Images

Examples of Comorbidities

There are many different possibilities when it comes to comorbidities. Physical illnesses such as diabetes and high blood pressure are often co-occurring conditions. Mental illnesses often co-occur with each other and with substance abuse. A comorbid condition can also include a physical illness and a mental illness (such as cancer and major depressive disorder).

Certain illnesses tend to co-occur with others for various reasons. It could be that the risk factors are the same for both diseases. This makes a person with one disease likely to get another one. Another possibility is when one disorder actually causes another.

Also, the symptoms of one illness can make a person more likely to develop another. For example, anxiety and depression can make a person likely to self-medicate with drugs or alcohol.

Common Comorbidities

Diabetes and obesity commonly occur together. Each of them also has its own list of comorbidities.


Obesity is known to predispose people to many comorbid illnesses. In fact, there are approximately 236 medical problems (including 13 types of cancer) linked with obesity, according to the Obesity Medicine Association.

Common comorbidities for those who are obese include:

  • Insulin resistance (a condition that is considered a precursor to type 2 diabetes)
  • Type 2 diabetes
  • High blood pressure
  • Dyslipidemia (high blood lipid levels including high cholesterol)
  • Cardiovascular disease
  • Stroke
  • Arthritis
  • Sleep apnea
  • Gallbladder disease
  • Hyperuricemia (excess levels of uric acid in the blood, a risk factor for gout)
  • Osteoarthritis
  • Certain types of cancer, such as breast cancer, colorectal cancer, and gallbladder cancer
  • Depression

Reasons why obesity and these other conditions are thought to be comorbid:

  • Carrying around excess weight can put physical stress on the joints resulting in comorbidities such as osteoarthritis. Excess weight can push on the chest and diaphragm. This can cause the soft tissues of the neck to collapse, leading to sleep apnea.
  • An increase in hormones and other substances secreted by adipose (fat) tissue impacts the endocrine system, resulting in diabetes and other metabolic conditions.
  • Physical and metabolic problems can harm the body's organs, such as the heart and kidneys.


Common conditions associated with diabetes include:


Obesity and type 2 diabetes often co-occur, and both conditions are also associated with other chronic illnesses such as kidney disease and osteoarthritis.

Psychiatric Comorbidities

According to the Substance Abuse and Mental Health Services Administration’s (SAMHSA) 2018 National Survey on Drug Use and Health, nearly 9.2 million adults in the United States have a comorbidity that includes substance abuse and a mental illness, or two types of mental illness, such as anxiety and depression.

Dual Diagnosis

A substance use disorder can involve alcohol or drug addiction (or both). Comorbid substance use disorder and mental illness is also called a dual diagnosis, and less frequently referred to as MICD (mental illness/chemical dependency).

The National Institute on Drug Abuse reports that nearly half of those who have one condition—either mental illness or substance abuse—also have the other.

Those with a substance use disorder are more likely to have a mental illness, and individuals with mental illness are more likely to have substance use disorder. One reason for this is that some symptoms of mental illness can cause people to self-medicate with drugs or alcohol.

Furthermore, chronic drug or alcohol use can have a negative influence on the brain, making a person more likely to develop mental illness.

Depression and Anxiety

One of the most common examples of comorbidity in the mental health field is depression and anxiety disorder. According to the National Alliance on Mental Illness (NAMI), some sources estimate that nearly 60% of those with anxiety also have symptoms of depression and vice versa.

Some of the most common mental health disorders in people with substance use disorder include mood and anxiety disorders such as:

  • Major depression
  • Persistent depressive disorder
  • Bipolar disorder
  • Post-traumatic stress disorder
  • Panic disorder
  • Social anxiety
  • Generalized anxiety disorder
  • Obsessive-compulsive disorder

Those with conditions considered to be serious and persistent mental illnesses (SPMI) are at the highest risk of having co-occurring mental health and substance use disorders. SPMI diagnoses, sometimes referred to as thought disorders, include:

  • Schizophrenia
  • Schizoaffective disorder (a chronic disorder that involves hallucinations, delusions and symptoms of a mood disorder)


Substance use disorders (like alcohol and drug addiction) often co-occur with mental illnesses like anxiety and depression. One reason for this is that symptoms of these illnesses can cause a person to find relief with alcohol or other drugs.


Finding the right treatment for someone with comorbidities often requires consultation and planning between various healthcare providers and organizations. This applies to those with multiple mental health conditions as well as those with physical comorbidities.

After being hospitalized, people with multiple health problems often need assistance and support from organizations such as home healthcare agencies and social services. These organizations can address situations such as being unable to work due to a major disability. They can also arrange for physical care, housing, and more.


Comorbidity means you have more than one illness (physical or mental) at once. There are many different causes of comorbidity. Some diseases, like obesity and diabetes or anxiety and depression, commonly overlap. There are many different theories for why certain diseases tend to be comorbid.

A Word From Verywell

Comorbidities can be challenging to live with. You may need to see a few different types of health care providers before you find the right treatment plan for you. Successful treatment may require a combination of medications and lifestyle changes. Sometimes treating one condition (such as obesity) can also cure the other (such as diabetes).

Frequently Asked Questions

  • What does comorbidity mean?

    Comorbidity is the presence of two or more medical conditions at the same time or back-to-back. An example is having diabetes and coronary artery disease.

  • What does comorbidity mean in psychiatry?

    In psychiatry, comorbidity is the presence of one or more diagnoses, such as obsessive-compulsive disorder and an eating disorder, or substance use disorder and anxiety.

  • Are comorbidities and complications the same thing?

    With comorbidity, there are two or more co-occurring medical conditions that develop independently of each other, even though there may be shared risk factors. A complication is an adverse event that arises as a direct consequence of a disease, such as diabetic kidney disease in people with type 2 diabetes or AIDS dementia in someone with HIV.

  • What is the Charlson Comorbidities Index?

    The Charlson Comorbidities Index is a system used to predict mortality (how long someone will live) in people with comorbid conditions in order to determine how aggressively a condition needs to be treated. Each comorbid condition is scored on a scale of 1 (such as for diabetes) to 6 (such as for metastatic cancer) and then added together for the final score.

Was this page helpful?
12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Klein DN. Different reasons for comorbidity require different solutionsWorld Psychiatry. 2004;3(1):28.

  2. Obesity Medicine Association. Diseases related to obesity.

  3. Khaodhiar L, McCowen KC, Blackburn GL. Obesity and its comorbid conditions. Clin Cornerstone. 1999;2(3):17-31. doi:10.1016/s1098-3597(99)90002-9

  4.  National Association of Managed Care Physicians. Co-morbidities.

  5. Substance Abuse and Mental Health Services Administration. Key substance use and mental health indicators in the United States: Results from the 2018 National Survey on Drug Use and Health.

  6. National Institute of Drug Abuse. DrugFacts. Comorbidity: Substance use disorder and other mental illnesses.

  7. Salcedo B. National Association of Mental Illness (NAMI). The comorbidity of anxiety and depression.

  8. Behavioral Health Evolution. Co-occuring disorders.

  9. National Institute on Drug Abuse. Common comorbidities with substance use disorders research report: What are the treatments for comorbid substance use disorder and mental health conditions?

  10. Ording AG, Sorenson HT. Concepts of comorbidities, multiple morbidities, complications, and their clinical epidemiologic analogs. Clin Epidemiol. 2013;5:199-203. doi:10.2147/CLEP.S45305

  11. Van Loo HM, Romeijn JW. Psychiatric comorbidity: fact or artifact? Theor Med Bioeth. 2015;36(1):41-60. doi:10.1007/s11017-015-9321-0

  12. Roffman CE, Buchanan J, Allison GT. Charlson Comorbidities Index. J Physiother. 2016 Jul;62(3):171. doi:10.1016/j.jphys.2016.05.008