Healthy people differ significantly in their overall personality, mood, and behavior. Each person also varies from day to day, depending on the circumstances. However, a sudden, major change in personality and/or behavior, particularly one that is not related to an obvious event (such as taking a drug or losing a loved one), often indicates a problem.
Changes in personality and behavior can be roughly categorized as one of the following:
These categories are not disorders. They are just one way doctors organize different types of abnormal thought, speech, and behavior.
People may have more than one type of change. For example, people with confusion due to Alzheimer disease sometimes become depressed, and people with delirium may have disorganized speech or hallucinations.
Confusion and delirium (see Delirium) refer to a disturbance of consciousness. That is, people are less aware of their environment and, depending on the cause, may be excessively agitated and belligerent or drowsy and sluggish. Some people alternate between being less alert and being overly alert. Their thinking appears cloudy and slow or inappropriate. They have trouble focusing on simple questions and are slow to respond. Speech may be slurred. Often, people do not know what day it is, and they may not be able to say where they are. Some cannot give their name.
Delusions are fixed false beliefs that people hold despite evidence against those beliefs. Some delusions are based on a misinterpretation of actual perceptions and experiences. For example, people may feel persecuted, thinking that a person behind them on the street is following them or that an ordinary accident is purposeful sabotage. Other people think that song lyrics or newspaper articles contain messages that refer specifically to them. Some beliefs seem more plausible and can be difficult to identify as delusions because they could occur or have occurred in real life. For example, people occasionally are followed by government investigators or have their work sabotaged by coworkers. In such cases, a belief can be identified as a delusion by how strongly people hold the belief despite evidence against it. Other delusions are easier to identify. For example, in religious or grandiose delusions, people may believe they are Jesus or the president of the country. Some delusions are quite bizarre. For example, people may think that their organs have all been replaced by machine parts or that their head contains a radio that receives messages from the government.
Disorganized speech refers to speech that does not contain the expected logical connections between thoughts or between questions and answers. For example, people may jump from one topic to another without ever finishing a thought. The topics may be slightly related or entirely unrelated. In other cases, people respond to simple questions with long, rambling answers, full of irrelevant detail. Answers may be illogical or completely incoherent. Occasionally misspeaking or intentionally being evasive, rude, or humorous is not considered disorganized speech.
Disorganized behavior refers to doing quite unusual things (such as undressing or masturbating in public or shouting and swearing for no apparent reason) or to being unable to behave normally. People with disorganized behavior typically have trouble doing normal daily activities (such as maintaining good personal hygiene or obtaining food).
Hallucinations refers to hearing, seeing, smelling, tasting, or feeling things that are not there. That is, people perceive things, seemingly through their senses, that are not caused by an outside stimulus. Any sense can be involved. The most common hallucinations involve hearing things (auditory hallucinations), usually voices. The voices often make derogatory comments about the person or command the person to do something. Not all hallucinations are caused by a mental disorder. Some types of hallucinations are more likely to be caused by a neurologic disorder. For example, before a seizure occurs, people may smell something when there is no smell (an olfactory hallucination).
Mood extremes include outbursts of rage, periods of extreme elation (mania) or depression, and, conversely, constant expression of little or no emotion (appearing unresponsive or apathetic).
Although people sometimes assume that changes in personality, thinking, or behavior are all due to a mental disorder, there are many possible causes. All causes ultimately involve the brain, but dividing them into four categories can be helpful:
Of these causes, drugs are the most common cause overall, followed by mental disorders.
Drugs may affect personality or behavior when they cause
Rarely, certain antibiotics and drugs used to treat high blood pressure cause changes in personality and behavior.
Mental disorders include
Disorders affecting mainly the brain include
Bodywide disorders that also affect the brain include
Less commonly, Lyme disease, sarcoidosis, syphilis, or a vitamin deficiency causes personality and behavior changes.
During the initial evaluation, doctors try to determine whether symptoms are due to a mental or physical disorder.
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
In people with changes in personality or behavior, certain symptoms and characteristics are cause for concern. They include
When to see a doctor:
People who have warning signs should be taken to the hospital right away. Law enforcement may need to be called if people are violent or belligerent.
If people take drugs for diabetes, a fingerstick test to check their blood sugar level should be done if possible. For this test, the finger is pricked to obtain a small sample of blood. If this test cannot be done or if the blood sugar level is low, people should be taken to the hospital right away.
People who have no warning signs should see a doctor within a day or two if the personality or behavior change was recent. If the change occurred gradually over a period of time, people should see a doctor as soon as is practical, but a delay of a week or so is not harmful.
What the doctor does:
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination, including a neurologic examination. What they find during the history and physical examination often suggests a cause of the changes and the tests that may need to be done (see Table).
Doctors ask when symptoms began. Many mental disorders begin in a person's teens or 20s. If a mental disorder begins during middle age or later, especially if there is no obvious trigger (such as loss of a loved one), the cause is more likely to be a physical disorder. A physical disorder is also more likely to be the cause when mental symptoms change significantly during middle age or later in people with a chronic mental disorder. If changes began recently and suddenly in people of any age, doctors ask about conditions that can trigger such changes. For example, they ask whether people have just started or stopped taking a prescription drug or a recreational (usually illegal) drug.
Doctors ask about other symptoms that may suggest a cause, such as
People are also asked whether they have previously been diagnosed and treated for a mental or seizure disorder. If they have been treated, doctors ask whether they have stopped taking their drugs or decreased the dose. However, because people with mental disorders may also develop physical disorders, doctors do not automatically assume that any new abnormal behavior is caused by the mental disorder.
During the physical examination, doctors look for signs of physical disorders, particularly
Confusion and delirium are more likely to result from a physical disorder. People with mental disorders are rarely confused or delirious. However, many physical disorders that cause changes in behavior do not cause confusion or delirium, but they often cause other symptoms that may appear to be a mental disorder.
Doctors bend the person's neck forward. If doing so is difficult or painful, meningitis may be the cause. Doctors check the legs and abdomen for swelling, which may result from kidney or liver failure. If the skin or whites of the eyes look yellow, the cause may be liver failure.
|PrintOpen table in new window
Typically, doctors clip a sensor to the person's fingertip to measure the oxygen level in the blood (called pulse oximetry). They also measure blood sugar (glucose) levels and blood levels of any anticonvulsants the person is taking.
For most people known to have a mental disorder, no further testing is needed if their only symptoms are worsening of their typical symptoms, if they are awake and alert, and if results of their physical examination are normal. For most other people, the following additional tests are usually done.
Some doctors also routinely do blood tests to measure electrolyte levels and to evaluate kidney function.
Other tests are done based mainly on the symptoms and examination results (see Table). They include
The underlying condition is corrected or treated when possible. Whatever the cause, people who are a danger to themselves or others typically need to be hospitalized and treated whether they are willing or not. Many states require that such decisions be made by someone appointed to make health care decisions for the mentally ill person (see Default Surrogate Decision Making). If the person has not appointed a decision maker, doctors may contact the next of kin, or a court may appoint an emergency guardian. People who are not dangerous to themselves or others can refuse evaluation and treatment, despite the difficulties their refusal may create for themselves and their family.
Last full review/revision December 2012 by Caroline Carney Doebbeling, MD, MSc