Diagnosis

Diagnosis, in medicine, the determination of the nature of a disease. Modern diagnosis combines the taking of the patient's health history, a physical examination, and laboratory and radiological examinations.

Some diseases, such as measles and mumps, are fairly easy to identify by appearance. Other problems, such as broken bones, are often suspected on the basis of symptoms and confirmed by X-ray observation. With many symptoms, however, more complex testing is needed. Establishing the presence of a gastric ulcer, for example, is helped by inserting a tube called an endoscope into the stomach. Coronary artery disease may be suspected due to the presence of chest pains and an abnormal electrocardiogram (see Electrocardiography); definitive evidence, however, comes only from an angiogram, in which dye is injected into the coronary arteries (see Heart Diseases). A diagnosis of cancer often requires a biopsy, or microscopic examination of tissues. Diagnosis of disease in a fetus is now possible, in many cases, by using sound waves or by sampling amniotic fluid (see Amniocentesis).

Laboratory tests are becoming more important in diagnosis. Measurement of hormone levels identifies endocrine diseases. Enumeration of different kinds of cells in the blood, called a differential count, helps pinpoint anemias and some kinds of cancers. The culturing of body fluids or tissues to show the presence of specific microorganisms is essential to rational treatment of infections with antibiotics (see Antibiotic).

Many diseases, such as headaches, are difficult to diagnose because they may have many causes. Some neurological diseases, such as Huntington's disease, can be identified with certainty only after many years of observing the patient's symptoms. To sharpen their diagnostic skills, physicians and other medical professionals hold regular conferences at which difficult cases are discussed.

Mental Illness

Mental Illness, disorder characterized by disturbances in a person’s thoughts, emotions, or behavior. The term mental illness can refer to a wide variety of disorders, ranging from those that cause mild distress to those that severely impair a person’s ability to function. Mental health professionals sometimes use the terms psychiatric disorder or psychopathology to refer to mental illness.

There are no blood tests, imaging techniques, or other laboratory procedures that can reliably diagnose a mental illness. Thus, the diagnosis of mental illness is always a judgment or an interpretation by an observer based on the speech, ideas, behaviors, and experiences of the patient.

For the most part, mental health professionals determine the presence of mental illness in an individual by conducting an interview intended to reveal symptoms of abnormal behavior. That is, the professional asks the patient questions about his or her mental state: “Do you hear voices of people who are not with you?” “Have you felt depressed or lost interest in most activities?” “Have you experienced a marked increase or decrease in your appetite?” “Have you been sleeping less than normal?” “Are you easily distracted?” The answers to these questions will suggest other questions. Eventually, the clinician will feel that he or she has enough information to determine whether the patient is suffering from a mental illness and, if so, to make a diagnosis.

Mental health professionals use a number of methods to treat people with mental illnesses. The two most common treatments by far are drug therapy and psychotherapy. In drug therapy, a person takes regular doses of a prescription medication intended to reduce symptoms of mental illness. Psychotherapy is the treatment of mental illness through verbal and nonverbal communication between the patient and a trained professional. A person can receive psychotherapy individually or in a group setting.

Depression

Depression (psychology), mental illness in which a person experiences deep, unshakable sadness and diminished interest in nearly all activities. People also use the term depression to describe the temporary sadness, loneliness, or blues that everyone feels from time to time. In contrast to normal sadness, severe depression, also called major depression, can dramatically impair a person’s ability to function in social situations and at work. People with major depression often have feelings of despair, hopelessness, and worthlessness, as well as thoughts of committing suicide.

Depression can take several other forms. In bipolar disorder, sometimes called manic-depressive illness, a person’s mood swings back and forth between depression and mania. People with seasonal affective disorder typically suffer from depression only during autumn and winter, when there are fewer hours of daylight. In dysthymia (pronounced dis-THI-mee-uh), people feel depressed, have low self-esteem, and concentrate poorly most of the time—often for a period of years—but their symptoms are milder than in major depression. Some people with dysthymia experience occasional episodes of major depression. Mental health professionals use the term clinical depression to refer to any of the above forms of depression.

Antidepressant

Antidepressant, medication used to treat depression, a mood disorder characterized by such symptoms as sadness, decreased appetite, difficulty sleeping, fatigue, and a lack of enjoyment of activities previously found pleasurable. While everyone experiences episodes of sadness at some point in their lives, depression is distinguished from this sadness when symptoms are present most days for a period of at least two weeks. Antidepressants are often the first choice of treatment for depression.

The first antidepressants, developed in the 1950s, are the tricyclic antidepressants (TCA) and the monoamine oxidase (MAO) inhibitors. TCAs block the reuptake of neurotransmitters into the presynaptic neurons, keeping the neurotransmitter in the synapse longer, and making more of the neurotransmitter available to the postsynaptic cell. TCAs include amitriptyline, doxepin, imipramine, nortriptyline, and desipramine.

MAO inhibitors decrease the rate at which neurotransmitters are broken down by the body so they are more available to interact with neurons. MAO inhibitors currently available in the United States include phenelzine and tranylcypromine.

Another group of antidepressants, known as selective serotonin reuptake inhibitors (SSRI), became available in 1987. SSRIs block the reuptake of the neurotransmitter serotonin into presynaptic neurons, thereby prolonging its activity. There are currently four SSRIs available for use in the United States: fluoxetine, sertraline, paroxetine, and fluvoxamine. Of this group, the best known is fluoxetine, commonly known by its brand name, Prozac.

Another antidepressant is venlafaxine, which works like TCAs but does not share their chemical structure, and it also causes different side effects. The antidepressant nefazodone prevents serotonin from binding to neighboring neurons at one specific binding site (serotonin can bind to neurons on many sites). It also weakly blocks the reuptake of serotonin.

Levodopa

Levodopa (Laradopa), the most effective antiparkinson drug available, an oral drug introduced in 1967 that treats bradykinesia, rigidity, tremor, and difficulty walking. Levodopa’s structure enables it to enter the brain, where it transforms into dopamine.

When levodopa is taken alone, however, the body breaks down about 95 percent of the drug into dopamine before it reaches the brain. Instead of being used by the brain, the dopamine travels throughout the body, producing side effects, including nausea and vomiting, before it is broken down, or metabolized, by the liver and other tissues. Combining levodopa with a drug such as carbidopa enables more levodopa to enter the brain before it converts into dopamine. Carbidopa/levodopa (Atamet, Sinemet) lessens rigidity and bradykinesia but is less effective in treating tremor or balance problems. A similar drug combining carbidopa and benserazide (Madopar) is available in Canada and Europe.

Carbidopa/levodopa produces side effects in some people. As many as half of the people who take this drug for two to five years begin to notice fluctuations in the drug’s effectiveness, known as an on-off effect. Others develop dyskinesia—involuntary movements such as jerking or twitching. As Parkinson disease progresses, the effectiveness of carbidopa/levodopa decreases and patients need higher and more frequent doses to control their symptoms. Depending upon the severity of symptoms, most doctors combine carbidopa/levodopa with other drugs to enhance levodopa’s effects.