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Comorbidities

Reviewed by: HU Medical Review Board | Last reviewed: September 2023

Comorbidities are 2 or more health conditions diagnosed in the same person. These diagnoses can happen at the same time or one after another, sometimes years apart. They may be related or unrelated to each other.1,2

Comorbidities are different from complications. Complications are physical or behavioral changes related to a health condition. For example, gaining weight as a result of depression is a complication. But over time, weight gain may increase the risk of developing diabetes or heart disease, which are comorbidities.1-3

Major depressive disorder (MDD) has many potential comorbidities. Learn about some of them below.

Mental health conditions

There are several mental health conditions that often occur with MDD. Experts do not know the exact reason for this. It may be that these conditions share similar risk factors. These risk factors may include:4-6

  • Changes in chemical balance in the brain
  • Family history
  • Exposure to trauma or stress

Also, some people may have personality traits that make them more likely to develop mental health conditions.4-6

The rates and risks of each mental health condition that can occur with MDD vary. But the most common conditions include:4,5

  • Generalized anxiety disorder (GAD)
  • Attention deficit hyperactivity disorder (ADHD)
  • Post-traumatic stress disorder (PTSD)
  • Eating disorders, such as anorexia or bulimia
  • Obsessive-compulsive disorder (OCD)
  • Panic disorder
  • Borderline personality disorder

Your doctor can help monitor you for signs of any other mental health issues. Your MDD treatment plan may need to be adjusted if a new condition arises.7

Substance use disorder (SUD)

Substance use disorder (SUD) is a medical condition. The substance a person uses can be alcohol, tobacco (nicotine), or recreational drugs. SUD is different from occasional substance use. Common signs of SUD include:8,9

  • Taking larger amounts of a substance and for longer periods
  • Spending a lot of time or money getting the substance
  • Craving the substance
  • Needing more of the substance to experience the same effects (tolerance)
  • Having unpleasant physical symptoms when not taking the substance (withdrawal)
  • Using the substance in a way that is not safe (like drinking and driving)
  • Being unable to complete daily responsibilities because of substance use or its effects
  • Having interpersonal or employment issues because of substance use

People with MDD have higher rates of SUD. The reverse is also true. Although the link between these 2 is known to be strong, there is still much more to understand. Some experts think the issues share common risk factors or affect the brain in similar ways.4-6,8

The desire to self-medicate MDD also can increase the risk of developing SUD. On the other hand, certain substances lead to depression-like symptoms.4-6,8

Physical comorbidities

Outside of mental health comorbidities like those above, depression is linked to many physical health issues, too. The links between depression and various other health conditions can vary. But research suggests that people who have depression alongside another medical condition have worse outcomes from that condition than those without depression.4-6

Certain health conditions can increase the risk of developing depression. This may be the case for serious or life-threatening issues like cancer. Other times, depression symptoms may increase the risk of a new health problem. An example is having trouble sleeping that becomes severe enough to be diagnosed as a sleep disorder.4-6

But the relationship between MDD and its comorbidities is not always one-way. Depression and another condition might feed off of each other and make each other worse. This back-and-forth cycle can lead to significant symptoms and lower quality of life. Depression is very common and can occur alongside other issues of varying nature.4,6

Regardless of the exact relationship, depression often occurs with other physical health conditions. As many as 70 percent of people with depression have at least 1 other medical diagnosis. Nearly 30 percent have 3 or more health conditions. There are many conditions that occur with depression.4,6,10

Examples of common medical comorbidities

Common medical comorbidities of MDD include:4-6,10

  • Heart disease (including heart attacks)
  • Diabetes
  • High blood pressure (hypertension)
  • Arthritis
  • Stroke
  • Parkinson’s disease
  • Asthma
  • Cancer
  • Chronic obstructive pulmonary disease (COPD)
  • Dementia
  • HIV

In some cases, the link between 2 conditions is clearer than in others. For example, it makes sense that distress from a new cancer diagnosis might lead to an episode of depression. But sometimes, it is unclear whether there is a link between different conditions.6

What conditions a person with MDD is at risk for depends on their:7

  • Personal health history
  • Prescription drugs
  • Family history
  • Environmental exposures

If you are concerned about your risk of developing a comorbid condition, talk with your doctor. They can help determine what symptoms to look out for and what tests may be needed. They also may be able to adjust your treatment plan to address more than one condition at once. This may be helpful for managing comorbid mental health conditions.7

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