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The term schizophrenia was first used in 1911 by Eugen Bleuler, a Swiss psychiatrist, to categorize patients whose thought processes and emotional responses seemed disconnected. The term schizophrenia literally means split mind; however, many people still believe incorrectly that the condition causes a split personality (which is an uncommon problem involving dissociation).
Schizophrenia is now used to describe a cluster of symptoms that typically includes the following:
Delusions.
Hallucinations.
Disordered thinking.
Emotional unresponsiveness.
Because symptoms of schizophrenia arise from various physical processes and respond differently to treatments, some experts recommend classifying the disease based on the presence of the following symptom groups:
Negative symptoms (including apathy and social withdrawal).
Psychotic symptoms.
Disordered thinking. (Some experts group psychotic and disordered thinking in a single category called positive symptoms.)
The disease is complicated by the fact that although a schizophrenic patient may have more than one symptom, he or she rarely has all of them. Symptoms also often go into remission. As the mechanisms in the brain that lead to schizophrenia are being discovered, researchers are attempting to define more accurate ways of describing the disease as it relates to the biologic processes that cause them.
Negative Symptoms
Negative symptoms reflect the following states:
Diminishment of the self.
Lack of emotions.
Colorless speaking tones.
A general loss of interest in life and the ability to experience pleasure. (One study reported that patients were able to experience unpleasant odors in a normal way, but not pleasant ones.)
Inappropriate affect (a condition in which the patient displays inappropriate reactions to an event (e.g., laughing hysterically over a loss).
Often certain negative symptoms (e.g., lack of responsiveness and poor sociability) appear in childhood as the first indications of schizophrenia. Certain imaging techniques suggest that these findings are based on biologic changes in specific parts of the brain. In many patients, however, negative symptoms do not appear until after positive symptoms develop. Negative symptoms tend to be more common than positive symptoms in older patients and typically persist after positive symptoms have been treated.
Psychotic Symptoms
Psychotic symptoms, particularly delusions and hallucinations, are the most widely recognized manifestations of schizophrenia.
Hallucinations. Hallucinations are the experiences of seeing, hearing, tasting, smelling, or feeling things that don't exist. Auditory hallucinations are false senses of sound, such as hearing voices that go unheard by others. They are the most common psychotic symptoms, affecting about 70% of patients. One study even reported that schizophrenic patients who had been profoundly deaf since birth were able to describe convincing experiences of hearing voices.
Delusions. Delusions are fixed, false beliefs. They can be bizarre (e.g., invisible aliens have entered the room through an electric socket) or nonbizarre (e.g., unwarranted jealousy, or the paranoid belief in being persecuted or watched).
After the initial event, psychotic symptoms usually occur episodically and are interspersed with periods of remission. They typically occur in men between the ages of 17 and 30 and in women between the ages of 20 and 40.
Cognitive Impairment (Disordered Thinking)
The symptoms of cognitive impairment and disordered thinking include the following and may occur before other symptoms of schizophrenia:
A lack of attention.
Impaired information processing and an aberrant association between words and ideas. Sometimes this condition is so extreme that speech becomes incoherent and is referred to as "word salad." Patients may connect words because of similarity of sound, rather than by meaning, a condition known as "clang associations."
Memory impairment. In keeping with other aspects of disordered thinking, memory impairment in schizophrenia is likely to involve the inability to connect an event with its source into a complete and whole memory. For instance, a patient may recall and even feel a familiarity with a specific event but be unable to remember where, when, or how it took place.
Backward masking dysfunction. This is a trait in which a distraction causes a person to forget a preceding event. It might be an important symptom and a marker of schizophrenia even in people with normal working memories. As an example of a test used to diagnose this trait, the patient is given an item to look at, such as four letters on a computer screen. The screen goes blank and another image called a masking stimulus appears (such as four broken letter fragments). The patient is then asked to type in the original letters. Both symptomatic and presymptomatic patients commonly have problems with this particular exercise.
In summary, people with schizophrenia do poorly on mental tasks requiring conscious awareness, such as verbal fluency, short-term and working memory, and processing speed. However, they are no worse than the general population in underlying (implicit) learning, such as grammar skills, vocabulary, and spatial skills (e.g., map reading). Some experts believe that impaired verbal memory in schizophrenia is a consequence of depression and slowness, but not a result of the disease process.
Other Symptoms
People with schizophrenia may experience other symptoms, such as intolerance of heat (which is associated with antipsychotic medications) and a reduced sense of smell.
WHAT CAUSES SCHIZOPHRENIA?
No single cause can account for all cases of schizophrenia. Rather, it appears to be the result of multiple hits from genetic factors, environmental and psychological assaults, and possible hormonal changes that alter the brain's chemistry and trigger this devastating disease.
Brain Structure and Circuitry
Abnormalities of Brain Volume and Activity. Imaging techniques have revealed reduced volume and actual loss of tissue in the brains of people with schizophrenia. Of particular importance are volume losses and abnormal activity in the prefrontal cortex and the temporal lobes .
Reductions in volume of the prefrontal cortex have been observed in many patients with schizophrenia. This area affects verbal memory, attention, reasoning, aggression, and meaningful speech. (Not all patients have the same deficits. For example, one study reported that patients with paranoid schizophrenia tend to have preserved left prefrontal volumes.)
Overactivity in the specific parts of the frontal and the right temporal lobes has been associated with auditory hallucinations (e.g., hearing voices).
Loss of volume in the temporal lobe affects the limbic areas (located deep in the brain), which contain the hypothalamus, amygdala, and hippocampus. Activity in this area is related to emotions and memory, and abnormalities are associated with positive symptoms, including delusions and hallucinations, and also with disordered thinking. Some evidence suggests that abnormalities here occur after the disease process has started or may only indicate a susceptibility to the disease.
Abnormal Brain Chemicals. Schizophrenia is associated with an unusual imbalance of neurotransmitters (chemical messengers between nerve cells) and other factors.
Abnormalities in dopamine receptors. Imbalances in the neurotransmitter dopamine are important research targets in schizophrenia. Dopamine overactivity is now known to be closely linked to reduced prefrontal cortex activity. Over-activity, particularly the left side, is associated with psychotic symptoms and appears to be due to an increase in specific chemical receptors, particularly those called C1 and D1. (These receptors attract and lock dopamine.)
Abnormalities in glutamate receptors. Glutamate, an amino acid known to affect dopamine and excite nerve activity, is also under scrutiny. For example, glutamate binds to N-methyl-D-aspartate (NMDA) receptors, which play a critical role in healthy nerve development and may be abnormal in schizophrenia. Abnormalities in NMDA and other molecules in the glutamate pathway appear to play significant roles in impairment of mental function and development of negative symptoms.
Abnormal Circuitry. Abnormalities in brain structure are also reflected in the disrupted connections between nerve cells that are observed in schizophrenia. Such miswiring could impair information processing and coordination of mental functions. For example, auditory hallucinations may be due to miswiring in the circuits that govern speech processing. Strong evidence suggests that schizophrenia involves decreased communication between the left and right sides of the brain.
Loss of reelin. A protein called reelin, which is involved in the nerve cell architecture, is also being investigated. Studies have observed abnormally lower levels of reelin in the prefrontal cortex region of patients with both schizophrenia and bipolar psychosis, perhaps contributing to psychosis and to impaired information processing.
Genetic Factors
Schizophrenia undoubtedly has a genetic component. The risk for inheriting schizophrenia is 10% in those who have one immediate family member with the disease and about 40% if the disease affects both parents or an identical twin. Family members of patients also appear to have higher risks for the specific symptoms (i.e., negative or positive) of the relative with schizophrenia.
Researchers are seeking the specific genetic factors that may be responsible for structural brain abnormalities, including reduced brain size and enlarged ventricles, that have been observed in patients with schizophrenia and their families. For example an abnormal so- gene called COMT may make people susceptible to deficits in the prefrontal cortex of the brain, where schizophrenia develops.
It should be noted that heredity does not explain all cases of the disease, however. About 60% of people with schizophrenia have no close relatives with the illness.
Approximately 15 percent of people who suffer from major depression also show symptoms of psychotic depression . These symptoms include hearing voices inside one's head (auditory hallucinations), having visions of people or things that are not actually there (visual hallucinations), and delusional thinking. People who suffer from this extreme form of major depression are in need of immediate attention. Because they cannot rationally judge the consequences of their actions, they are in serious danger of killing themselves.