What is multiple diagnosis called? Understanding Comorbidity, Multimorbidity, and Dual Diagnosis

October 1, 2025 •

3 min read

Over 50% of adults aged 65 and older have three or more chronic health problems. The formal term for what is multiple diagnosis called is often comorbidity or multimorbidity, each with specific nuances that influence a patient's care plan and treatment strategy.

Quick Summary

The term for having multiple diagnoses depends on the specific context, referring to comorbidity, multimorbidity, or dual diagnosis. These terms describe the presence of multiple illnesses, chronic conditions, or co-occurring mental health and substance use disorders.

Key Points

Comorbidity defined: Refers to a condition that co-occurs with an index disease, with one diagnosis often considered the primary focus of treatment.
Multimorbidity defined: Describes the co-occurrence of two or more chronic conditions without any single condition holding priority, emphasizing a holistic view of the patient.
Dual diagnosis specifics: A subtype of comorbidity where a person has both a mental health disorder and a substance use disorder.
Management challenges: Having multiple diagnoses complicates treatment due to potential drug interactions, conflicting care plans from different specialists, and a higher burden on the patient.
Patient-centered care: An integrated, coordinated, and patient-centered approach is crucial for effective management and can lead to better outcomes for individuals with multiple conditions.
Increasing prevalence: The presence of multiple chronic conditions is common, particularly in older populations, and is a growing public health challenge.

Differentiating Key Terminology

When a patient has more than one health condition, it is a complex clinical situation described by several distinct terms. The exact name used depends on the number and type of conditions and whether a specific 'index' disease is the primary focus. Acknowledging these differences is crucial for effective diagnosis, treatment, and understanding the patient's overall health picture.

Comorbidity

Comorbidity refers to the simultaneous presence of two or more medical conditions in a patient. This term is often used when focusing on a primary disease, with other conditions considered in relation to it. For example, a specialist treating a patient for a specific condition might consider other coexisting conditions as comorbidities because they can impact the treatment plan. The coexisting conditions can be independent or related to the primary condition.

Multimorbidity

Multimorbidity describes the co-occurrence of two or more chronic conditions without prioritizing any single one. This term captures the overall complexity of a patient's health. Public health bodies often use this term to describe the situation of people living longer with multiple chronic illnesses. From a patient perspective, multimorbidity is a more holistic concept, acknowledging the impact of all health problems.

Dual Diagnosis (or Co-Occurring Disorders)

Dual diagnosis specifically refers to the presence of both a mental health disorder and a substance use disorder in the same individual. This is common, as many people with a substance use disorder also have a mental illness, and vice versa. Integrated treatment is important for dual diagnosis because these conditions significantly influence each other. For instance, depression might lead to alcohol use, and substance abuse can worsen mental health symptoms.

Comparison of Key Multiple Diagnosis Terms


Feature	Comorbidity	Multimorbidity
Focus	One primary or 'index' disease and its co-existing conditions.	The overall burden of all co-occurring chronic conditions, with no single focus.
Application	Often used by specialists who focus on treating one specific disease, like an oncologist or cardiologist.	Often used in primary care to consider the total impact of all conditions on a patient's health and quality of life.
Context	Clinical guidelines may center on managing the primary condition while considering how comorbidities affect it.	Management strategies require a broader, more patient-centered approach that balances the care for multiple conditions.
Examples	Diabetes viewed as a comorbidity to a primary diagnosis of heart disease.	A patient with coexisting heart disease, diabetes, arthritis, and depression, with no one condition prioritized.

The Complexity of Multiple Diagnoses

Managing patients with multiple diagnoses, especially multimorbidity, is challenging for healthcare providers. Conditions can interact in complex ways, potentially worsening each other.

Key challenges include:

Treatment Complexity: Treatment plans can be complicated, and medications for one condition might negatively affect another. Taking multiple medications also increases the risk of interactions.
Care Coordination: Seeing several specialists for multiple diagnoses can lead to fragmented care and conflicting advice if communication is poor. This can also result in duplicated tests and higher costs.
Patient Burden: Patients face the burden of managing frequent appointments, coordinating providers, and following complex treatment plans.

Common Combinations of Diagnoses

Many physical and mental health conditions commonly occur together due to shared risk factors or because one condition can make another more likely.

Common comorbidities and co-occurring disorders include diabetes and heart disease, anxiety and depression, COPD and cardiovascular disease, arthritis and obesity, chronic pain and mental health disorders, and substance use disorders and mental illness. You can find more details on these common combinations in {Link: PubMed Central https://pmc.ncbi.nlm.nih.gov/articles/PMC7613517/}.

Effective Management Strategies

Patient-centered care is a crucial strategy for managing multiple diagnoses. This approach focuses on the individual's needs, goals, and preferences, empowering them to actively participate in their healthcare.

Key strategies for effective management include integrated treatment, shared decision-making, care coordination, focusing on the patient experience, and regular assessments. More information on patient-centered care and these strategies is available in {Link: PubMed Central https://pmc.ncbi.nlm.nih.gov/articles/PMC7613517/}.

Conclusion

While terms like comorbidity, multimorbidity, and dual diagnosis exist, what is multiple diagnosis called ultimately signifies recognizing a patient's complex health profile. These terms highlight different care approaches, from focusing on a primary illness to a more holistic, patient-centered view. As more people live with multiple chronic conditions, especially older adults, a coordinated, integrated, and empathetic approach is increasingly important. More information can be found in {Link: PubMed Central https://pmc.ncbi.nlm.nih.gov/articles/PMC7613517/}.

Frequently Asked Questions

The official terminology for having two or more diseases at the same time is 'comorbidity' or 'multimorbidity.' 'Comorbidity' is often used when one condition is the primary focus, while 'multimorbidity' describes the overall burden of multiple chronic conditions without prioritizing any single one.

A dual diagnosis, also known as a co-occurring disorder, is a specific type of comorbidity where an individual has both a mental health disorder and a substance use disorder simultaneously.

Comorbidity involves having one or more conditions alongside a designated primary or 'index' disease. In contrast, multimorbidity refers to having multiple chronic conditions where no single disease is considered primary over the others, focusing on the cumulative impact on the patient.

Yes, having multiple diagnoses is common, especially among older adults. Studies have shown that over 50% of adults aged 65 and older have three or more chronic conditions.

Treating multiple diagnoses is challenging due to the potential for complex interactions between conditions and medications, the need for multiple specialists, and the heavy burden placed on the patient to manage their care.

Common examples of comorbidities include the co-occurrence of diabetes, high blood pressure, heart disease, and arthritis. In mental health, examples include the co-occurrence of anxiety and depression.

Improving care for multiple diagnoses requires a patient-centered approach that emphasizes care coordination, integrated treatment plans, and shared decision-making between the patient and their healthcare team.