Münchausen syndrome is not a somatoform disorder, but its features are somewhat similar in that mental health problems underlie physical symptoms. The key difference is that people with Münchausen syndrome consciously fake the symptoms of a physical disorder. They repeatedly fabricate illnesses and often wander from hospital to hospital for treatment.

However, Münchausen syndrome is more complex than simple dishonest fabrication and simulation of symptoms. The disorder is associated with severe emotional problems. People with the disorder are usually quite intelligent and resourceful; they not only know how to mimic diseases but also are sophisticated with regard to medical practices. They can manipulate their care to be hospitalized and subjected to intense testing and treatment, including major operations. Their deceits are conscious, but their motivation and quest for attention are largely unconscious.

Münchausen by proxy is a bizarre variant of Münchausen syndrome in which a child is used as a surrogate patient, usually by a parent. The parent falsifies the child's medical history and may injure the child with drugs or add blood or bacterial contaminants to urine specimens, all in an effort to fake disease. The motivation underlying such bizarre behavior appears to be a pathologic need for attention and for an intense relationship with the child.

The term psychosomatic disorder usually is applied when a person has physical symptoms that appear to be caused or worsened by psychologic factors, rather than by some underlying physical disease. This does not imply, however, that physical symptoms are imaginary or are being faked (as in Munchausen syndrome); the symptoms are actually being experienced by the person. Thus, psychosomatic disorders require that the psychologic factors and the physical symptoms be consistently and closely connected in time.

Unlike somatoform disorders, psychosomatic disorders do not fit into specific diagnostic categories, and they manifest in a variety of ways. Social and psychologic stress can also aggravate a wide variety of physical diseases, including diabetes mellitus, coronary artery disease, and asthma.

Stress can cause physical symptoms even when no physical disease is present. For example, hives can be brought on entirely by a psychologic reaction. In some cases, physical symptoms result from the body's automatic response to emotional stress, as when heart rate and blood pressure increase in response to fear. In other cases, psychologic symptoms become physical symptoms in an unconscious attempt to divert attention away from a troublesome emotional issue.

Sometimes a physical symptom is a metaphor for the person's psychologic problem, as when a person with a “broken heart” experiences chest pain. Other times, a physical symptom reflects identification with another person's pain. For example, a person may have chest pain after a family member or friend has had a heart attack. Finally, a psychologic symptom may become a physical symptom as a way of reexperiencing a symptom of a previous physical disorder. For example, a person who once had a painful bone fracture may reexperience that sort of bone pain when a psychologic symptom becomes bone pain. Physical symptoms that evolve from psychologic symptoms tend to be mild and transient. The process of psychologic symptoms becoming physical symptoms can affect people who do not have a serious underlying mental health disorder. Anyone can undergo this process. The resulting symptoms can be difficult for a doctor to diagnose, and a person is likely to undergo various diagnostic tests to eliminate the possibility of an underlying physical disorder.

Psychologic factors can also indirectly influence the course of a disease. For example, a person with high blood pressure may deny having it or deny its seriousness. Denial is a defense mechanism that helps reduce anxiety. However, denial may prevent a person from complying with treatment. In this case, the person with high blood pressure may fail to take his prescribed medication, thus worsening the condition. Conversely, physical disease can lead to a psychologic condition. For example, people with life-threatening, recurring, or chronic physical disorders commonly become depressed. The depression, in turn, may worsen the effects of the physical disease.