Comorbidity

Large-scale population studies suggest that a person with any psychiatric disorder is at a higher risk for all other mental illnesses. However, comorbidity seems to be much more common between some conditions than others. These associations appear bidirectional, meaning that the conditions are likely to be linked no matter which one appears first.

Psychological conditions with high rates of comorbidity include:

• Major depressive disorder (MDD)¹ 
• Anxiety disorders, such as generalized anxiety disorder (GAD) or panic disorder (PD)
• Eating disorders (ED)
• Substance use disorders (SUD)²
• Bipolar disorder (BP)
• Schizophrenia
• Obsessive-compulsive disorder (OCD)

There may be a significant amount of overlap among these highly comorbid conditions. For instance, global surveys suggest that roughly 46% of individuals with MDD will also experience an anxiety disorder within their lifetime. Substance use disorders are similarly correlated with other commonly comorbid conditions such as depression, bipolar disorder, and eating disorders. 

The high prevalence of comorbidity in mental disorders may be partly explainable by underlying risk factors that can contribute to multiple conditions. Psychological stress may be one notable candidate. Persistent and severe stress may contribute to the onset of many different psychiatric conditions, including depression, bipolar disorder, posttraumatic stress disorder,³ and anxiety disorders.

Genetic factors may also increase a person’s risk for multiple mental illnesses. Researchers have identified many gene variants that are associated with more than one type of psychological or neurodevelopmental disorder. For example, many of the inherited risk factors for schizophrenia are also linked with bipolar disorder and major depressive disorder. Similarly, autism spectrum disorder (ASD),⁴ attention-deficit/hyperactivity disorder (ADHD), and intellectual disabilities show apparent genetic linkages.

Certain kinds of adversity early in life may also decrease a person’s overall psychological resilience, leaving them vulnerable to a wide range of mental disorders. Childhood risk factors for comorbid mental illness may include:

• Poverty
• Malnourishment
• Abuse or neglect from authority figures
• Bullying
• Growing up in a city

Physical damage to the brain can also disrupt a variety of different cognitive and emotional functions, placing an individual at risk for more than one mental illness. Psychiatric comorbidity may be more likely following brain cell death due to things like:

• Traumatic brain injuries
• Cardiovascular disease and strokes
• Meningitis (brain inflammation)
• Use of intoxicating substances

Comorbid mental illnesses can present a major challenge to mental health professionals in the long term. Co-occurring conditions can increase an individual’s psychological distress and decrease their ability to function in daily life. The symptoms of one disorder may also interfere with efforts to manage others. For example, some studies have found that patients with ADHD are less likely to follow their prescribed medication regimens when they’re also living with other mental disorders and chronic conditions.

Mental health care practitioners offering mental health services can modify their treatment plans in many different ways to adapt to these challenges and help clients improve their quality of life. In practice, care may have to be tailored to the specific symptoms, personal experiences, medical histories, and treatment goals of individual patients. However, some strategies that commonly help in cases of psychiatric comorbidity include:

• Lifestyle changes to promote overall mental health
• Multiple medications to address varied symptoms
• Medical support for conditions like heart disease, diabetes, or chronic illness
• Higher doses of relevant medications
• Treatments focused on shared causes of mental illness, such as trauma
• Transdiagnostic cognitive-behavioral therapy (CBT)
• Longer courses of treatment with ongoing maintenance

When designing treatment plans for clients with multiple co-occurring conditions, mental health professionals may need to be cautious about possible unwanted interactions between various disorders. As noted in Psychiatric Times, for instance, some antidepressant medications may worsen anxiety unless the patient begins with small doses and increases them gradually. Since anxiety can be a common comorbid condition with depression, it can be beneficial for clinicians to be alert for these kinds of side effects.

Substance use disorders occurring alongside other psychiatric conditions can be particularly difficult to treat. Increasing evidence shows that these individuals may respond best to an integrated treatment approach that addresses multiple disorders at once. This often involves cognitive-behavioral therapies aimed at reinforcing a client’s belief in their ability to change and their motivation to do so. Integrated treatment may focus on helping individuals build life skills, develop support networks, and learn coping strategies that may help them manage their symptoms.

Getting help for co-occurring mental illnesses often begins with a referral from a primary care doctor. Practicing physicians can typically recommend mental health practitioners qualified to deliver integrated or trauma-focused care. Individuals seeking help may also be able to find treatment providers through their insurance agencies. In addition, local community organizations and religious clergy can often recommend experienced psychiatrists or counselors.

There are also quite a few non-profit and governmental organizations dedicated to promoting mental health. These groups often provide educational resources and searchable databases for people in search of treatment. Some may also have helplines where those living with mental illness can find support. Notable examples include:

Another option is to seek mental health care online. This can be a helpful avenue for people who have difficulties finding treatment due to busy schedules, limited mobility, geographic isolation, or other obstacles. Platforms like BetterHelp can provide many different kinds of therapy, including cognitive-behavioral therapy (CBT), one of the most commonly recommended treatments for those with comorbid mental illnesses. Clinical trials have found that online CBT can be an effective treatment for comorbid conditions such as anxiety and depression.