What Is Co-Morbidity?

Living with a chronic or long-lasting health condition is challenging. A second condition can make it harder still.

Chronic conditions require long-term strategies to manage symptoms. When two or more conditions occur together, diagnosis can become more difficult, treatment for one condition can complicate the other and the conditions can interact in ways that make symptoms of both worse.

At FHE Health, we help patients manage co-occurring conditions. Depression and anxiety often present together, for example, and ADHD can occur alongside anxiety disorders. When a patient has multiple mental health conditions, preexisting conditions may affect both diagnosis and treatment. Our mental health professionals work as part of a multidisciplinary team to treat the physical, cognitive and emotional symptoms of mental illness.

What Is Comorbidity?

Comorbidity means a person has two or more medical conditions at the same time. The term can describe multiple physical illnesses, multiple mental health disorders or a combination of physical and mental health concerns.

Comorbidity vs. Co-Occurring Disorders

Although these terms are related, each has a distinct use in health care:

Depression and alcohol use disorder, for instance, would be described as co-occurring disorders.

How Common Is Comorbidity?

Comorbidity is common in behavioral health care. According to the Substance Abuse and Mental Health Services Administration’s 2024 National Survey on Drug Use and Health, about 21.2 million U.S. adults had both a mental illness and an SUD in 2024. Research also suggests that about half of people with an SUD also have a mental health disorder.

Mental health conditions frequently overlap, with symptoms that may reinforce or complicate one another. Someone with depression, for example, may experience persistent anxiety at the same time.

Why Comorbidity Happens

Rather than stemming from a single cause, comorbid conditions often reflect a combination of influences. Genetic vulnerabilities may leave someone susceptible to multiple disorders, especially when combined with trauma, chronic stress or other environmental pressures.

The connection between comorbidity, addiction and mental health may develop over time. Someone experiencing emotional distress might turn to alcohol or drugs for relief. Continued use, however, can worsen the original symptoms or produce new ones during intoxication and withdrawal. Since each condition may contribute to the onset or progression of the other, clinicians often describe the relationship as bidirectional.

Common Comorbid Combinations

Certain combinations appear frequently in mental health and addiction treatment.

Depression and Anxiety

Depression and anxiety often occur together. Someone may feel persistently worried and tense while also experiencing low mood, fatigue or loss of interest. Treatment may include therapy, medication or both based on the patient’s needs. When addiction is also part of the picture, coping with anxiety and addiction brings its own challenges.

PTSD and Substance Use

Post-traumatic stress disorder (PTSD) is commonly found alongside substance use disorder. Some people use substances to numb intrusive memories, hypervigilance or sleep problems. Intoxication and withdrawal can then increase emotional distress.

ADHD and Substance Use

Attention deficit/hyperactivity disorder (ADHD) can affect attention, impulse control and emotional regulation. These challenges may increase vulnerability to risky substance use. Substance use may also mask ADHD symptoms or make them harder to evaluate.

Eating Disorders and Mood Disorders

Eating disorders often occur with depression or anxiety. Restrictive eating, bingeing or purging can affect concentration and emotional stability. Medical complications may further influence psychiatric symptoms.

Schizophrenia and Substance Use

People with schizophrenia may also misuse alcohol or drugs. Substance use can intensify symptoms and interfere with treatment. Certain substances may also cause psychosis, so clinicians must examine when symptoms began.

Mental Health and Physical Health Comorbidity

Physical symptoms can take a significant emotional toll, illustrating how closely the mind and body are connected. Living with chronic pain, for example, may disrupt sleep and contribute to depression or substance misuse. As a person’s mood declines, staying active and managing the pain can become even harder.

A similar cycle can occur with diabetes. The Centers for Disease Control and Prevention (CDC) notes that untreated mental health issues can make diabetes harder to manage, while the demands of the condition can strain mental health. People with diabetes are two to three times more likely to have depression than people without diabetes. When depression causes low energy or motivation, patients may struggle to follow treatment plans and attend medical appointments.

How Comorbid Conditions Interact

One disorder can resemble or conceal another. Difficulty concentrating, for instance, could be associated with ADHD, depression, anxiety, poor sleep or substance use.

Conditions may also intensify each other. Anxiety can disrupt sleep, while sleep loss may increase anxiety. Depression can reduce motivation to engage in treatment, allowing other health concerns to worsen.

Medication adds another consideration. A medication that helps one disorder may cause side effects or interact negatively with other substances.

Why Comorbidity Complicates Treatment

Pinpointing the source of a symptom becomes difficult when several conditions overlap. Changes in sleep, energy or concentration could stem from a physical illness or a mental health disorder. Intoxication and withdrawal can further complicate the assessment by producing symptoms that resemble anxiety, depression or psychosis.

Before longer-term therapy begins, clinicians may need to address an urgent concern such as severe withdrawal or suicidal thoughts. Prioritizing safety does not mean setting the other conditions aside. Once the patient is stable, treatment should account for each diagnosis and the ways the conditions affect one another.

If you or someone you know is in crisis or having thoughts of suicide, call or text 988 to reach the 988 Suicide & Crisis Lifeline, or call 911.

How Comorbid Conditions Are Diagnosed

A comprehensive assessment gives clinicians an initial picture of the patient’s health. Along with discussing current symptoms, they examine when each concern began and how it has changed over time. Medical records, substance use patterns and previous treatment experiences can provide further context.

Diagnosis may evolve as treatment progresses. During detox and early stabilization, the effects of intoxication or withdrawal can be difficult to distinguish from an independent psychiatric disorder. Observing which symptoms remain after a period without substance use often brings the underlying conditions into clearer focus. Clinicians can then refine the diagnosis and treatment plan.

Integrated Treatment Approaches

Integrated treatment brings mental health, substance use and medical services into a coordinated plan. The right combination depends on the diagnoses, symptom severity and immediate risks.

Detox and Stabilization

When physical dependence is present, detox may be the first stage of care. Medical supervision helps manage withdrawal and identify urgent concerns. After stabilization, patients can continue treatment for both the SUD and other conditions.

Therapy

Cognitive behavioral therapy can help patients examine connections among thoughts, emotions and behavior. Other approaches may address trauma, emotional regulation or interpersonal concerns.

Medication Management

Medication may help manage psychiatric symptoms or support recovery from certain SUDs. Prescribers consider the patient’s medical history, current substance use and potential medication interactions. Ongoing monitoring helps them evaluate progress and side effects.

Levels of Care

Options may include residential treatment, partial hospitalization, intensive outpatient care or standard outpatient services. FHE Health’s continuum of care allows treatment intensity to adjust with the patient’s needs.

Supporting Long-Term Recovery

Long-term recovery may involve continued therapy, psychiatric care or medical follow-up. Peer support can provide connection and accountability throughout this process.

Progress often depends on circumstances outside the treatment setting. Housing instability, legal problems or difficulty finding work can create stress that makes recovery harder to sustain. FHE Health offers case management, including legal counsel, to help patients address these issues and build a more stable foundation for managing their health.

Frequently Asked Questions

Treatment for Co-Occurring Conditions at FHE Health

At FHE Health, our multidisciplinary team creates individualized treatment plans for people with complex mental health, substance use and physical health needs. Our integrated services include psychiatric care, therapy, medication management and substance use treatment across multiple levels of care, through our co-occurring disorder treatment program.

Our treatment center also serves people with primary mental health conditions who do not have a history of substance use. If you or a loved one needs support, contact FHE Health to discuss treatment options with our team.