Mental Health and Behavior

Mental Health and Behavior Changes in behavior and personality

By Michael B. First, MD, Columbia University
Last complete review / verification November 2017 by Michael B. First, MD
NOTE: This is the Patient Version. CLICK HERE to access the Professional version

Healthy people have significant variability in their overall personality, mood and behavior. Each person also has daily variability, depending on the circumstances. However, a sudden and important change in personality and / or behavior, especially if not related to an easily recognizable event (such as taking a drug or losing a loved one), is often indicative of a problem . (See also Overview of mental illnesses).
Variations in personality and behavior can be broadly classified as:
Confusional state or delirium
Speech or disorganized behavior
Extreme changes in mood (like depression)
These categories are not disturbances. They represent only one way in which physicians organize different types of abnormal thinking, language and behavior.
These changes in temperament and behavior may be caused by physical or psychological state issues.

People can present more than one type of variation. For example, people with a confused state due to a drug may sometimes have hallucinations and people with extreme changes in mood may have delusions.
Confusional state and delirium
Confusional state and delirium refer to disorders of consciousness. In other words, subjects are less aware of their environment and, depending on the cause, can be very agitated and aggressive or sleepy and lazy. Some of them go from a state of hypoattention to one of over-attention. Their design appears confused and slowed down or inadequate. They find it difficult to concentrate on easy questions and respond late. Speech can be disjointed. Often, subjects do not know what the current day is and may not know where they are. Some do not know how to report their names.


The fixations are false and stable beliefs which the subjects do not renounce despite the contrary proofs. Some fixations are based on errors of interpretation of perceptions and real experiences. For example, subjects may feel persecuted, believing that a person behind them on the road is following them or that a simple accident is intended sabotage. Other people believe that song lyrics or newspaper articles contain messages that specifically refer to them.
Some beliefs seem more plausible and can be difficult to identify as fixations because they can occur or have occurred in real life. For example, people are sometimes followed by law enforcement or their work is sabotaged by colleagues. In these cases, a belief can be identified as a fixation on the degree of people's attachment to belief despite evidence to the contrary.
Other fixations are easier to identify. For example, in religious or large manias, subjects may believe they are Jesus or the president of a nation. Some fixations are extravagant. For example, some subjects may believe that their organs have all been replaced by mechanical parts or that their head contains a radio that receives government messages.

Disorganized speech

Disorganized speech refers to a way of expressing oneself that does not follow the logical connections expected between thoughts or between questions and answers. For example, subjects can jump from one topic to another without even concluding a thought. The topics can be quite connected to each other or completely disconnected. In other cases, the subjects answer simple questions with long, inconsistent speeches full of irrelevant details. The answers may be illogical or completely inconsistent.
Inconsistent or intentionally evasive, rude or ironic language that is occasionally encountered is not considered disorganized speech.

Disorganized behavior

Disorganized behavior refers to doing unusual things (such as stripping or masturbating in public or shouting and cursing for no apparent reason) or not being able to behave normally. People with disorganized behavior usually have difficulty performing normal daily activities (such as maintaining good personal hygiene or getting food).


Hallucinations refer to feeling, seeing, smelling, tasting or trying things that do not exist. In other words, subjects perceive things, apparently through their senses, that are not caused by an external stimulus. They can involve any sense. The most common hallucinations are sound (auditory hallucinations), usually voices. The voices often make offensive comments about the subject or order the subject to do
Systemic disorders that also affect the brain
Systemic disorders that also affect the brain include:
Kidney failure
Hepatic failure
Low blood sugar (hypoglycemia)
Systemic lupus erythematosus (lupus)
Disorders of the thyroid, such as a hypoactive (hypothyroidism) or overactive (hyperthyroidism) thyroid gland
Less frequently, also Lyme disease, sarcoidosis, syphilis or a vitamin deficiency induce changes in personality and behavior.
During the initial assessment, doctors try to determine if the symptoms are due to a physical or mental disorder.
The following information can help people decide if a doctor's assessment is required and what it can entail.

Alarm signals

In people with changes in personality or behavior, some symptoms and features are signs to watch out for. These warning signs include:
Symptoms that arise suddenly
Attempts at self-harm, harming others or threatening to do so
Confusional state or delirium
Severe headache
Symptoms suggestive of a brain malfunction, such as difficulty walking, balance or slurred speech or vision problems
A recent head injury (within a few weeks)
When to consult a doctor
Persons with warning signs should be visited by a healthcare professional as soon as possible. If the person is violent, mandatory medical treatment may be required.
The person who shows no signs of alarm must visit a doctor within a day or two if the change in personality or behavior has occurred recently. If this change has occurred gradually over time, the person should go to a doctor as soon as possible, even if a delay of a week or so does not pose any danger.

How the doctor behaves

The doctor starts by asking the patient questions about symptoms and medical history. Subsequently, he performs an objective examination, with a neurological evaluation and an examination of the mental state (which, among other things, evaluates the ability to pay attention, memory and mood). What is found during the anamnestic evaluation and physical examination is often indicative of the underlying cause of the changes and suggests the tests to be performed (some causes and characteristics of changes in personality and behavior).
The questions include when the symptoms started. Many mental disorders arise during adolescence or within 20 years. If a mental disorder begins during middle age or late age, especially if there is no obvious cause (such as the loss of a loved one), the most likely cause of the disorder is physical. A physical disorder is also the most likely cause when mental symptoms change significantly in middle age or in later years in people with chronic mental disorder. If changes have occurred recently and suddenly, in people of any age, doctors ask questions about the conditions that might have triggered them. For example, they ask if the subject has just started or stopped a treatment with a prescription drug or recreational substance (usually illegal).
Doctors ask about other symptoms that could be indicative of a cause, such as:
Palpitations: potentially attributable to an overactive thyroid gland or to the use of or withdrawal from a substance.
Tremors: Parkinson's disease or substance withdrawal.
Difficult walking or speech: multiple sclerosis, Parkinson's disease, stroke or opioid or sedative intoxication.
Headache: brain infection, brain tumor or cerebral bleeding (hemorrhage).
Numbness or tingling: stroke, multiple sclerosis or vitamin deficiency.
Subjects are also asked if they have previously received a diagnosis and treatment for a mental or convulsive disorder. In case of therapy, doctors ask if they have stopped taking their medications or reduced their dosage.
However, since individuals with mental disorders also can develop physical disorders, doctors don't mechanically assume that any new abnormal behavior is caused by a mental disturbance.

The doctor asks for any physical ailments (such as diabetes) and asks questions about lifestyle (such as marital status, work situation, level of education, use of alcohol and drugs for recreational use, as well as lifestyle habits). In addition, the doctor asks if some family members have had physical problems that can cause mental symptoms (such as multiple sclerosis).
During the physical examination, the doctors look for signs of physical disorders and altered mental status, especially:
fever (indicative of an infection, abstinence from alcohol or the use of amphetamines

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