Schizophrenia (cont.)
What causes schizophrenia?
Experts think schizophrenia is caused by several factors.
Genes and environment. Scientists have long known that schizophrenia
runs in families. The illness occurs in 1 percent of the general population, but
it occurs in 10 percent of people who have a first-degree relative with the
disorder, such as a parent, brother, or sister. People who have second-degree
relatives (aunts, uncles, grandparents, or cousins) with the disease also
develop schizophrenia more often than the general population. The risk is
highest for an identical twin of a person with schizophrenia. He or she has a 40
to 65 percent chance of developing the disorder.
We inherit our genes from both parents. Scientists believe several genes are
associated with an increased risk of schizophrenia, but that no gene causes the
disease by itself. In fact, recent research has found that people with
schizophrenia tend to have higher rates of rare genetic mutations. These genetic
differences involve hundreds of different genes and probably disrupt brain
development.
Other recent studies suggest that schizophrenia may result in part when a
certain gene that is key to making important brain chemicals malfunctions. This
problem may affect the part of the brain involved in developing higher
functioning skills. Research into this gene is ongoing, so it is not yet
possible to use the genetic information to predict who will develop the disease.
Despite this, tests that scan a person's genes can be bought without a
prescription or a health professional's advice. Ads for the tests suggest that
with a saliva sample, a company can determine if a client is at risk for
developing specific diseases, including schizophrenia. However, scientists don't
yet know all of the gene variations that contribute to schizophrenia. Those that
are known raise the risk only by very small amounts. Therefore, these "genome
scans" are unlikely to provide a complete picture of a person's risk for
developing a mental disorder like schizophrenia.
In addition, it probably takes more than genes to cause the disorder.
Scientists think interactions between genes and the environment are necessary
for schizophrenia to develop. Many environmental factors may be involved, such
as exposure to viruses or malnutrition before birth, problems during birth, and
other not yet known psychosocial factors.
Scientists are learning more about brain chemistry and its link to
schizophrenia.
Different brain chemistry and structure. Scientists think that an
imbalance in the complex, interrelated chemical reactions of the brain involving
the neurotransmitters dopamine and glutamate, and possibly others, plays a role
in schizophrenia. Neurotransmitters are substances that allow brain cells to
communicate with each other. Scientists are learning more about brain chemistry
and its link to schizophrenia.
Also, in small ways the brains of people with schizophrenia look different
than those of healthy people. For example, fluid-filled cavities at the center
of the brain, called ventricles, are larger in some people with schizophrenia.
The brains of people with the illness also tend to have less gray matter, and
some areas of the brain may have less or more activity.
Studies of brain tissue after death also have revealed differences in the
brains of people with schizophrenia. Scientists found small changes in the
distribution or characteristics of brain cells that likely occurred before
birth. Some experts think problems during brain development before birth may
lead to faulty connections. The problem may not show up in a person until
puberty. The brain undergoes major changes during puberty, and these changes
could trigger psychotic symptoms. Scientists have learned a lot about
schizophrenia, but more research is needed to help explain how it develops.
Scientists have learned a lot about schizophrenia, but more research is
needed to help explain how it develops.
Next: How is schizophrenia treated? »
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