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Causes of Mental Disorder Schizophrenia
Dominique B. Talley
Physiological Psychology
Essay 5

2. Mental disorders are beginning to widely affect the United States, numbers
reported by Robins and Regier in their 1991 paper Psychiatric disorders in America:
The epidemiological catchment area study suggest that nearly one-third of the
population may suffer from symptoms that are similar to those of psychiatric
disorders at some stage of life. The table shown below is taken from Biological
Psychology by Breedlove and Watson and gives a visual aid of the percentage of
adults in the United States suffering from psychiatric disorders.
Breedlove, Watson. Biological Psychology. Seventh Edition. An Introduction to
Behavioral, Cognitive, and Clinical Neuroscience. 2013
(Data from Kessler et al., 1994.)
Schizophrenia is a psychiatric disorder that has been classified as a disorder
with the following symptoms; auditory hallucinations, delusional thoughts that the
individual has falsely believed, and changes in emotions. The cause of the disorder is
an area that is still under research however a major identifiable cause of the
disorder has been linked to heritable component. Currently research is being

3. [TALLEY] 3
conducted to further link specific genes to the disorder in efforts to further study
the disorder. Data collected in Gottesman’s 1991 paper Schizophrenia genesis: The
origins of madness suggests a relationship between the degree in which a person is
related and the likelihood of development of the Schizophrenia. The data shows a
significant increase in likelihood of development of the disorder the closer two
individuals are related.
In efforts to further relate genes to the mental disorder schizophrenia
research on heritability and genetic inter-relationship of neurocognitive traits was
conducted and the relative heritability of thirteen standard measures of which one
being IQ1 was tested. From the data it was suggested that memory IQ and
visuomotor-processing speed formed two separate groups of traits that are shown
consistent in a particular family gene line. These two groups are suggested to be
associated with the NOS1AP gene on chromosome 12. This study strongly suggests
the heritability of specific neurocognitive traits, which is vital in the advancement of
research pertaining to genes related to the mental disorder Schizophrenia. In efforts
to further understand how neurological deficits, which have been directly related to
schizophrenic patients3, relate to or affect the daily function of patients studies were
conducted identifying the specific genes of neurocognitive traits. With identification
of particular genes endophenotypes for schizophrenia4 can be proposed.
Endophenotypes, which are heritable, state- independent biomarkers, related to an
1 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130778/
2 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130778/
3 http://www.ncbi.nlm.nih.gov/pubmed/8610818
4 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130778/

4. illness are seen at higher rates in related individuals. These endophenotypes can
suggest of the presence of a disorder prior to the actual diagnosable pathology of the
disorder is available5. This could potentially be a major stepping-stone in
understanding the cause of schizophrenia.
With possible endophenotypes being classified for schizophrenia the mental
disorder can be further studied on a smaller scale. While endophenotypes are
considered state- independent, they can be present and studied in healthy
individuals6 in addition to individuals suffering from the disorder. The ability to
minimize heterogeneity allows for a more focused study. The study of
endophenotypes of healthy individuals display data supporting the cause of the
disease which can be compared to the effects of the disease7 which could be seen in
the endophenotypes of affected individuals.
While new research is constantly being conducted on the mental disorder in
efforts to relate to specific susceptible genes to the mental disorder schizophrenia,
data has shown that the term endophenotype has been used to describe certain
characteristics that show deviation amongst affected individuals8. One of the five
potential endophenotypes for schizophrenia, MMN, does not show “unequivocally”
impairment or strong supporting data suggesting impairment in newly diagnosed
5 http://en.wikipedia.org/wiki/Endophenotype
6 Bechara J. Saab, John C. Roder
Vol.5 No.1 ˑ Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, Toronto,
Canada; M5G 1X5 Department of Molecular and Medical Genetics, Program in
Neuroscience; University of Toronto; Toronto, Canada; M5G 2M9 - See more at:
http://www.hypothesisjournal.com/?p=720#sthash.JeGByRkt.dpuf
7 http://www.hypothesisjournal.com/?p=720
8 http://schizophreniabulletin.oxfordjournals.org/content/33/1/69.full

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patients or unaffected first-degree relatives9. This data suggest evidence of other
factors contributing to the development of the disorder. While a hereditable
component exists, research suggests other components may play a role in the
display of certain symptoms of the disorder.
In conclusion due to the complexity of the genetic material of humans the
exact cause of schizophrenia is still being considered and studied. Evidence strongly
supports a heritable component of the mental disorder that can be related to
endophenotypes. Shifting from the study of generalized symptoms of schizophrenia
to the more focused characteristics and heritability of neurocognitive traits with
relations to schizophrenia will allow for the possible quick detection and possible
prevention of the mental disorder.
9 http://schizophreniabulletin.oxfordjournals.org/content/33/1/69.full