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Causes of Schizophrenia: Genetics and Environment
Numerous studies indicate that schizophrenia has a strong genetic component.
Irving Gottesman (1991) compiled data showing that the risk of developing
schizophrenia increases with the degree of biological closeness to someone
suffering from the disorder. While the general population has a 1 percent risk of
developing schizophrenia, the chance of being diagnosed with the disorder
increases to 9 percent if a sibling is afflicted. If an identical twin is diagnosed with
schizophrenia, the likelihood of the other twin developing the disorder jumps to 50
percent.
The fact that dizygotic (fraternal) twins show a higher rate of concordance than
non-twin siblings (17 percent compared to 9 percent) indicates that the prenatal
environment may playa role in developing schizophrenia. Mothers who contract
rubella or influenza during the second trimester of pregnancy aretwice as likely to
give birth to children who develop the disorder (Brown et al., 2000). However,
whether this risk factor is due to the virus itself, the mother's immune response,
medications taken to combat the virus, or another, unknown factor, is still unclear.
If schizophrenia were entirely controlled by genes, the risk of twoidentical twins
both developing the disorder should be close to 100 percent. That the concordance
rate ishalf this suggests that both genetics and environment play significant roles
in the development of schizophrenia. Some psychologists propose the diathesisstress hypothesis, which suggests that people are genetically predisposed to a
particular mental disorder but will develop the disorder only if they are exposed to
environmental or emotional stress during critical developmental periods.
Schizophrenia: What is It?
Literally meaning "split mind," schizophrenia is often mistaken for dissociative
identity disorder, a controversial condition in which people claim to have multiple
personalities. However, schizophrenia actually refers to a person's split from
reality, characterized by distorted perceptions, inappropriate emotions or
reactions, and confusion. Schizophrenia is classified as a psychotic disorder or a
psychosis, which is a psychological disorder in which a person loses contact with
reality and expresses irrational ideas and distorted perceptions.
To be diagnosed with schizophrenia, a person must display two or more symptoms
for at least a month. People with schizophrenia often think or speak in ways that
are disorganized, illogical, or incoherent. Schizophrenics may also suffer from
delusions, which are persistent, false beliefs. For example, patients may believe
that they are being spied on, that someone is controlling their thoughts and actions,
or that people are being unfaithful to them. These delusions may be supported by
illogical thinking: Psychiatrist Silvana Arieti (1955) noted the huge gap in one
patient's reasoning when she asserted "The Virgin Mary was a virgin. I am a
virgin; therefore I am the Virgin Mary,"
A third symptom of schizophrenia is the existence of hallucinations: false sensory
perceptions that a person believes to be real. Hearing voices is the most common
type of hallucination; many schizophrenics report that they hear insulting
comments or receive orders from voices inside their heads. Research using fMRI
scans shows that verbal hallucinations in schizophrenics are accompanied by
activity in the brain regions normally associated with thought processing (Shergill
et al., 2000). While auditory hallucinations are most common, people may also see,
feel, smell, or taste things that aren't really there.
Schizophrenics often have difficulty acting appropriately in social situations. They
may become catatonic and remain motionless for several hours, or they may
become wildly agitated and talk or shout constantly.
Clusters of symptoms can help to categorize schizophrenia. People who show positive
symptoms reflect an excess or distortion of normal functions, such as delusions and
hallucinations. These symptoms tend to appear and disappear as the disorder recurs and goes into
remission. Disorganized symptoms, such as confused speech and flat emotion, follow the same
pattern. However, schizophrenics who display negative symptoms, or decreases in normal
functions such as attention or emotion, tend to exhibit more constant symptoms that are less
responsive to antipsychotic medications.
EXPLAINING SCHIZOPHRENIA: Cognitive and Neural Abnormalities
Cognitive deficits are a core feature of schizophrenia. People with schizophrenia tend to perform
poorly on many information processing tasks, particularly activities that require sustained
attention. Working memory is permanently and consistently impaired, while long-term memory
involving the acquisition and recall of new information may be severely impaired (Saykin et al.,
1991). Since it is difficult for people with schizophrenia to remember the source of a piece of
information, it is likely that they will be unable to distinguish between factual information and
fiction or imagination, resulting in the delusions characteristic of the disorder.
Do chemical imbalances in the brain explain schizophrenia? When researchers
examined the brains of schizophrenic patients after death, they discovered up to six times the
normal number of dopamine receptors (Seeman et al., 1993) The researchers believe that this
elevated level of dopamine may intensify brain signals in schizophrenic patients, causing
positive symptoms such as hallucinations and paranoia. Drugs that block dopamine transmission
have proved effective at reducing many of the symptoms of schizophrenia, whereas drugs that
increase dopamine action, such as cocaine or amphetamines, can exacerbate symptoms
(Swerdlow&Koob, 1987).
Recent research suggests that defects in the major receptor molecules for glutamate, another
neurotransmitter, may cause symptoms of schizophrenia. A glutamate deficiency is linked to the
negative symptoms associated with catatonic schizophrenia. This would account for general
cognitive defects, as well as explaining the effects of street drugs such as PCP (commonly
known as "angel dust"), which interfere with glutamate transmission and temporarily induce
schizophrenia-like symptoms in otherwise normal people.
Brain scans reveal that people with schizophrenia tend to have abnormal brain structures.
Many studies have found enlarged, fluid-filled areas and a corresponding shrinkage of cerebral
tissue in people with schizophrenia (Wright et al., 2000). Some studies have even found such
abnormalities in the brains of people who would later develop this disorder, and in their close
relatives. (Boos et al., 2007; Job et al., 2006).There is also evidence of abnormally low activity in
the frontal lobes (Pettegrew et al., 1993).
What causes these abnormal brain structures to form? Well, during adolescence the brain
selectively prunes unused neurons and connections. Some neuroscientists believe that abnormal
pruning may lead to the loss of too many cell bodies, potentially causing symptoms of
schizophrenia. Australian researcher Chris Pantelis and his colleagues took MRI scans of three
groups of young peopleone group of people who had recently been admitted to hospital with
schizophrenia, one group of people without schizophrenia, and one group of people who had
suffered from the disorder for around ten years. Pantelis discovered that the brains of the first
group were shrinking at twice the rate of those without schizophrenia, suggesting that the normal
developmental pruning process is accelerated in the brains of people with schizophrenia (Salleh,
2003).
Treating Schizophrenia
Antipsychotic drugs are a class of psychoactive medications used to treat disorders
in which psychotic symptoms, such as hallucinations, paranoia, and delusions,
predominate. There are two types: typical and atypical.
Although many typical antipsychotics have been around since the 1950s, they
continue to be as effective as newer medications at treating psychotic illnesses
such as schizophrenia. These drugs effectively reduce or eliminate the positive
symptoms of schizophrenia, such as hallucinations and delusions, by decreasing
dopamine activity at certain synapses in the brain (Lehman et al., 1998;
Lenzenweger et al., 1989). The relative effectiveness of these drugs indicates that
too much dopamine is at least partially responsible for schizophrenia (Pickar et
al., 1984; Taubes et al., 1994). A notable limitation of typical antipsychotics,
however, is that they do not treat negative symptoms. In addition, side effects of
typical antipsychotics can include sluggishness, tremors, and even tardive
dyskinesia, a serious and often irreversible motor disturbance in which the tongue,
face and other muscles involuntarily jerk or contract (Kaplan &Saddock, 1989). As
a result of these potentially severe side effects, people with psychotic illnesses
often find it difficult to continue taking antipsychotic medications for extended
periods of time.
For those afflicted with negative symptoms of schizophrenia, such as apathy or
prolonged lack of movement, atypical antipsychotics can provide relief. These
newer medications can alleviate negative symptoms by altering the activity of
other neurotransmitters, such as serotonin, in addition to dopamine. They are also
less likely to produce the major side effects caused by typical antipsychotics
because they target specific dopamine receptors in the brain. Examples of atypical
antipsychotics include Clozapine, Risperidone, and Olanzapine. Although atypical
antipsychotics generally produce fewer side effects than do typical antipsychotics,
both types of drugs can cause symptoms such as dizziness, weight gain, and
nausea.
AP Psychology
Schizophrenia Circuit
Name ___________________________
Please respond to the following questions based on each of the following sources.
Schizophrenia: What is It?
1. Why is schizophrenia considered to be a psychotic disorder?
2. What is the difference between a delusion and a hallucination?
3. Name and describe the three main categories of symptoms of schizophrenia.
1.
2.
3.
Causes of Schizophrenia: Genetics and Environment
1. What evidence exists to support the idea that schizophrenia has genetic causes?
2. What types of environmental factors contribute to the onset of schizophrenia?
3. Explain the diathesis-stress hypothesis.
Subtypes of Schizophrenia
Match each case study with the appropriate subtype of schizophrenia it best reflects.
Paranoid
Catatonic
Disorganized
Delusions of grandeur and Non-reaction to the
Disorganized speech,
persecution, often
environment, extreme
flattened or inappropriate
accompanied by
negativism, or wild
emotion
hallucinations
agitation
Case Study:
Case Study:
Case Study:
Undifferentiated
Varied symptoms
Explaining Schizophrenia: Cognitive and Neural Abnormalities
1. Identify two specific cognitive deficits associated with schizophrenia.
2. What role does dopamine play in causing schizophrenia?
3. A deficiency in glutamate is associated with which type of symptoms of schizophrenia?
4. Describe the abnormal brain structures associated with schizophrenia.
Treating Schizophrenia
1. How do typical antipsychotics eliminate the positive symptoms of schizophrenia?
2. What is tardive dyskinesia and why might it cause someone to stop taking typical
antipsychotic medication?
3. How do atypical antipsychotics help schizophrenics and what advantage do they have
over typical antipsychotics?
Anderson Cooper: Schizophrenia Simulator
1. What cognitive difficulties does Cooper exhibit during his schizophrenia simulation?
2. How does Cooper describe his experience? What caused him to feel empathy for people
with schizophrenia?