The Differences Between a Disease and a Disorder

The differences between a disease and a disorder are much more subtle than you might initially believe. Keep reading to learn what they are.
The Differences Between a Disease and a Disorder
Samuel Antonio Sánchez Amador

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 16 December, 2022

We all get sick from time to time in our lives, as we’re open systems that can be colonized by live pathogens or damaged by poor repair and sporadic mutations (such as cancer). Despite the fact that any human being knows how to describe what it’s like to be sick, it’s not as easy to distinguish at a terminological level the differences between a disease and a disorder.

Although they’re often used interchangeably, concepts such as syndrome, condition, disease, and disorder communicate slightly different ideas. Keep reading, because, in the following paragraphs, we’ll show you how to distinguish the 2 most important concepts regarding this topic.

The most relevant terms in the medical field

Before exploring the differences between a disease and a disorder, we want to define both terms in isolation and support them with other related concepts. Keep reading.

What’s a disease?

The World Health Organization (WHO) defines diseases as “the alteration or deviation of the physiological state in one or several parts of the body, for generally known causes, manifested by characteristic symptoms and signs, and whose evolution is more or less predictable .” It’s an integral part of life, just like health.

A disease can be caused by exogenous causes (bumps, bacteria, viruses, environmental conditions) or endogenous causes (autoimmune attacks or cancer cells). In humans, this set of physiological dysfunctions manifests itself with pain, distress, social problems, and even loss of life.

Diseases are characterized by appearing with objective and tangible signs (such as fever) and with subjective symptoms typical of the patient, such as pain. There are also diseases (or phases) that are asymptomatic. In this last group, the disease produces physiological changes, but they’re not tangible in part of the evolution (especially at the beginning).

For a disease to be such, it must meet at least 2 of these 3 requirements:

  1. Have a recognizable cause: The etiological agent must be registered or at least hypothesized. There are many diseases that are considered idiopathic (their cause is unknown), but at least the processes that lead to them are identified to a variable degree.
  2. Show an identifiable set of signs and symptoms: Although the perception of each patient is different, every disease has a series of common signs. Pathognomic signs are those that unequivocally show the presence of a disease.
  3. Present consistent anatomical alterations: A person can have back pain for 2-3 days, although it’s not considered pathological if it’s temporary and resolves on its own. The consistency of the signs defines what’s a disease and what’s not.

As you can see, not all the ailments that humans experience are diseases in the strictest sense of the word. For example, a headache isn’t a pathology by itself, but a symptom that may or may not indicate an underlying abnormal process.

A doctor looking at a chest x-ray.
Some signs of disease can be seen through diagnostic methods, such as X-rays.

What’s a disorder?

The dictionary of the National Cancer Institute (NCI) defines the term disorder as follows: “In medicine, a disturbance of normal functioning of the mind or body. Disorders may be caused by genetic factors, disease, or trauma.” This concept applies especially in the field of mental health.

In other words, a disorder is a change or alteration that occurs in the essence or permanent characteristics that make up a thing or in the normal development of a process. In this case, the process occurs within the human body and is abnormal, although not necessarily pathological.

This concept encompasses a wide range of terms, as disorders can be mental, physical, behavioral, genetic, emotional, and structural. Some of these fronts are linked to disease in its strictest sense, but others aren’t.

What’s a syndrome?

This concept’s usually used interchangeably with that of disorder, so it’s necessary to clarify some of its peculiarities. The NCI defines a syndrome as “A set of symptoms or conditions that occur together and suggest the presence of a certain disease or an increased chance of developing the disease.”

Syndromes have certain characteristics of their own that give them a more defined entity than that of other physiological imbalances. In other words, they manifest signs and symptoms that occur at a time and in a specific way. It should be noted that syndromes are multietological (semiological manifestations have several causes).

In medicine, this term has a negative connotation, however, in the biological field, it’s used more to describe natural events (pollination syndromes, for example).

What are the differences between a disease and a disorder?

Now we know what’s a disease, what’s a disorder, and what’s a syndrome. Now we’ll show you the differences between the first 2 concepts in the following sections. In any case, it’s important to keep in mind that not all sources agree on the same definition.

1. A disorder isn’t always a disease, but a disease always carries some disorder

The information portal Mundo Asperger gives the key to the distinction between both terms with a simple idea: A disorder can be considered as a description of one or a series of symptoms, actions, or behaviors, which may or may not be caused by a disease. In other words, it involves a change in physiological normality, although it’s not always accompanied by disease.

For example, an increase in heart rate above normal (more than 100 beats per minute) or tachycardia is a change in the normal physiology of the human body, therefore, it could be conceived as a cardiovascular disorder. This can be indicative of heart disease, but it can also be a sign that the person is very stressed.

A disorder indicates a state of abnormality at the organic level, while a disease shows a clear causality with a specific etiology. As we’ve said previously, for a person to be considered ill, there must be at least one process or etiological agent that justifies it.

2. Not all disorders have known etiologies

Another difference between a disease and a disorder lies in the specificity of the condition presented by the human being who suffers from it.

According to sources already cited, a disorder can also be conceived as a pathological state in which there’s insufficient evidence to assign it to a specific disease. For example, various types of autoimmune disorders are known to occur when protective cells in the body attack their host’s own tissues.

As indicated by the National Library of Medicine of the United States, there are more than 80 types of autoimmune disorders registered in humans, and (almost) all involve these general symptoms:

  • Fatigue
  • Fever
  • General discomfort
  • Joint pain
  • Rashes
  • 1 or more of these 3 physiological events: The destruction of some body tissue, the abnormal growth of an organ (spleen and liver, for example), and changes in organ function

An autoimmune disorder can be suspected when a patient comes to the clinic with these symptoms, but the exact disease that’s causing the disorder isn’t yet known. After performing many specific diagnostic tests, experts may discover that the person has multiple sclerosis, for example.

When a “label” is put on this condition, it’s still an autoimmune disorder, but now the causative disease, multiple sclerosis, is identified. At this point, it’s already possible to describe the etiology of the process.

3. Disorders are usually associated with the mental field

Undoubtedly, the clearest difference between a disease and a disorder is highlighted when the latter term is understood as the lack of normality on a cerebral and neurological level. Many media use the term disease to speak of a tangible and organic failure, while the term disorder is often associated with complex mental processes that are difficult to quantify.

The dictionary of the American Psychiatric Association (APA) defines mental disorder as “any condition characterized by cognitive and emotional disturbances, abnormal behaviors, impaired functioning, or any combination of these.” A disorder can never be attributed to the patient’s environmental context and often involves society, genes, and biochemistry.

Mental disorders can be chronic, cyclical (with episodes of remission and relapse), or occur as isolated events. Interestingly, in this field, most of them have a specific etiology (signs and symptoms) that makes them different from the rest.

A woman with a mental disorder in a therapy session.
Mental disorders receive this name because they meet specific criteria to be defined as such and not as diseases.

An example of a mental disorder: Generalized anxiety disorder (GAD)

Every few years, the APA publishes its Diagnostic and Statistical Manual of Mental Disorders (DMS). Together with the International Classification of Diseases (ICD), this document sets the standard for diagnostic criteria for psychiatric disorders.

Generalized anxiety disorder (GAD) is one of the best examples that we can think of to exemplify disorders in the emotional field and is characterized by the following criteria:

  1. The presence of excessive anxiety in the patient regarding a varied number of activities or events. The concern is more present than absent for a period of at least 6 months and is clearly excessive.
  2. Experienced worry is very difficult for the patient to control. It usually jumps from one topic to another but doesn’t disappear completely.
  3. Anxiety and worry are accompanied by at least 3 of the 6 symptoms cited in the patient (2 in children): The feeling of being on edge or lack of rest, ease of fatigue or being more fatigued than normal, difficulty with concentration, irritability, increased muscle aches or contractures, and difficulty sleeping.

Many mental disorders have a specific etiology, but others are more diffuse.

The differences between a disease and a disorder: A very subtle distinction

The differences between a disease and a disorder depend entirely on the definition given to the second term. Some conceive of disorders as a sign of physical maladjustment (such as tachycardia), others argue that it’s an unspecified general medical condition (autoimmune disorder), and there are even those who prefer to use the term only psychologically.

What’s more than clear to us is the following: A disease always carries a series of symptoms and signs, an underlying pathological process, and a consistent anatomical disorder. This term is much more circumscribed than that of disorder, and it’s more appropriate to use it when we refer to a specific illness in the clinical setting.

Este texto se ofrece únicamente con propósitos informativos y no reemplaza la consulta con un profesional. Ante dudas, consulta a tu especialista.