How an Organic Disease Differs From a Functional Disorder

Organic disease is one in which measurable changes are detected in cells, tissues, or organs of the body. In contrast, a functional disease causes symptoms, but the disease process is either unknown or it can't be measured by an agreed-upon scientific method or standard.

For example, abnormalities in a person's blood cell counts may point to an organic disease like cancer. In contrast, a functional disorder like fibromyalgia can be diagnosed despite there being no similar evidence to confirm it.

This article explains the difference between functional and organic diseases and lists some common examples of each. It also discusses difficulties in diagnosis, which is often the case with symptoms associated with mental health or psychosomatic disorders.

Examples of Organic Disease

Organic disease is a classification for many different types of illness. They can be localized (meaning they affect a specific part of the body) or systemic (affecting multiple organ systems).

They can be inherited (genetic) or caused by external or environmental forces. Some organic diseases are communicable, passed from one person to the next, while others are non-communicable.

Some of the broader categories and types of organic diseases include cancer, inflammatory illness, autoimmune diseases, and infectious disease.

Autoimmune Diseases

Autoimmune disease occurs when the body's immune system attacks its own cells and tissues. Examples include:

• Type 1 diabetes
• Multiple sclerosis (MS)
• Rheumatoid arthritis
• Lupus
• Psoriasis

Cancer

Cancer occurs when abnormal cells multiply unchecked and overtake healthy cells. Specific types of the cancers that are organic diseases include:

• Breast cancer
• Melanoma
• Leukemia
• Lymphoma
• Lung cancer
• Colon and rectal cancer

Inflammatory Diseases

Inflammatory diseases cause acute or progressive damage to cells and tissues due to inflammation. They include:

• Osteoarthritis
• Pelvic inflammatory disease (PID)
• Viral meningitis
• Atherosclerosis

Infectious Diseases

Infectious diseases occur when a bacteria, virus, fungus, parasite, or other microbe is transmitted between individuals. These diseases include:

• Hepatitis C
• Human immunodeficiency virus (HIV)
• Zika virus
• Tuberculosis
• Influenza

Examples of Functional Disorders

A non-organic disease is typically referred to as being functional, meaning that there are symptoms of illness but no clear measures by which to make a diagnosis.

The absence of measurable biomarkers doesn't mean that functional diseases don't exist; it simply means the causes are unknown (idiopathic).

Pruritus (itching) is one such example of a functional symptom. On its own, it is associated with neither a physical or biochemical change but remains a very real and tangible sensation. The same applies to:

• Fatigue
• Chronic headaches
• Insomnia

Examples of functional disorders defined and classified by their symptoms include:

• Irritable bowel syndrome (IBS)
• Chronic fatigue syndrome (CFS)
• Fibromyalgia
• Temporomandibular joint pain (TMJ)
• Gastroesophageal reflux disorder (GERD)
• Interstitial cystitis
  

Functional vs. Psychosomatic Symptoms

Psychiatric illnesses are also largely considered functional since the underlying cause is not readily identified. These include:

• Clinical depression
• Bipolar disorder
• Schizophrenia
• Attention deficit hyperactivity disorder (ADHD)
• Obsessive-compulsive disorder (OCD)
• Post-traumatic stress syndrome (PTSD)

However, a psychiatric illness is not the same thing as a psychosomatic one. Psychosomatic symptoms are those that are believed to be derived from the stresses and strains of everyday living.

They are driven by a person's mental or emotional state and often manifest with symptoms of:

• Backache
• Headache
• Fatigue
• High blood pressure
• Indigestion
• Shortness of breath
• Dizziness
• Sexual dysfunction (impotence)

Functional symptoms differ from psychosomatic ones in that the removal of the emotional stress may lessen the severity of symptoms but not entirely erase them.

In the past, functional disorders were largely considered psychosomatic. These conditions are now understood as having distinctive characteristics that define them irrespective of a person's emotional state.

Summary

Health conditions and disorders are typically described as being either an organic disease or a functional disease. The difference lies in the ability to measure and validate a diagnosis based on biomarkers for the disease and agreed-upon standards of identifying them.

Organic disease can be clearly identified, while functional disease remains idiopathic, or without a clear cause. It's not that functional diseases don't exist, but rather the shared understanding of the evidence for them.

Over time, medical advances have changed how certain functional diseases are now understood. It's likely that researchers will identify pathways to better identify organic disease processes at the root of illnesses now categorized as functional.