Negative symptoms
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Lack of expression – when a person’s face, voice tone and gestures seem flat, or looking disinterested in surroundings.
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Lack of motivation – having trouble doing simple things, not being able to get interested in everything, feeling sleepy.
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Lack of pleasure – not enjoying things they used to, including relationships and activities.
Theories of schizophrenia have attempted to explain the possible cause of this abnormality over the years. For the purpose of this essay, we are going to examine the following theories:
- Diathesis-stress model; This model says schizophrenia develops in people with an underlying biological vulnerability (diathesis) that is compounded by stress.
- The biological model: This model claims that schizophrenia is caused by genetic, neurotransmitter and structural brain fault or damage. The biological approach claims that schizophrenia is genetically inherited; that there is a high possibility of a first degree relative developing schizophrenia if one family member is diagnosed with schizophrenia.
There is a huge amount of evidence to suggest that schizophrenia can be in the family gene, and that it can be passed down generations which indicates it’s genetically inherited. In a study conducted by Chinese researchers in 2015 using classical genetic method i.e. ( family surveys, twin and adoption studies) it is argued that schizophrenia is a complex disease caused by genetic factors with a global heritability of more than 80% and a heritability of 82.9% in the Chinese Han population. (Cui D, et al, 2015). Most evidence comes from research using family studies and in particular the twin research. The twin research has shown over the years consistently that identical twins have a greater risk of developing schizophrenia, if their twin has the disorder, than non-identical twins. Monozygotic twins have a high possibility to develop schizophrenia and have a concordance rate at the range of 42 48% compared to dizygotic twins, 17 -18% concordance rate. (Gilmore, John H. 2010), (Jay, J 2004).
Some researchers argue that since monozygotic twins are born at the same time, they get treated similarly, and are often raised in a similar environment. The implication for this is that concordance rate between twins cannot be reliable according to this argument because if schizophrenia were genetically inherited then concordance rates should be closer to 100% as the twins would have been treated similarly; then we could argue that environmental factors can be an explanation of the cause of schizophrenia in a pair of monozygotic twins: the same can be mentioned for first degree relative because they will still share a similar environment which could provide an explanation for concordance rates. (Šagud, M, 2009), (Seglem, K et al, 2015).
A number of researches on adoptions support the claims that genetic factors play a part in the development of schizophrenia. For example a survey of 5500 adults adopted early in childhood shows that14% of their biological relatives were diagnosed with schizophrenia compared to 2.7% of their adopted relatives.). (Eyler, L, T., 2014. Similarly in a smaller survey of 164 adoptees whose biological mothers have been diagnosed with schizophrenia, 7% of these adoptees were diagnosed with the disorder as compared to 2% of the control group adoptees whose mothers do not have schizophrenia (Tucker-Drob, E,M. 2014)
The rate of schizophrenia in the general population is only 1%. The chances between the first degree relatives having the disorder is 12% and if both parents have the disorder it is 40% likely their siblings will have it. In comparison, schizophrenia only occurs in 2-3% between nephews. (Klahr, A M.2014)
Overall there is abundance of evidence to support the genetic premise of schizophrenia that makes its explanation plausible, thus creating an enabling environment for consistency and reliability for further research in this area of study.
We would like to acknowledge that genetic factor alone may not provide a complete explanation of schizophrenia as other biological explanations are also plausible. We shall examine other biological factors in the subsequent paragraph.
The dopamine hypothesis provides a second biological explanation of the cause of schizophrenia; that schizophrenia is caused by an increased reaction to dopamine in certain parts of the brain. Takase, M, 2015). Schizophrenia is due to dopamine overactivity in the pathways linking the midbrain to the limbic system, and the underactivity linking the midbrain to the cortex. It has been suggested that this could be because there is too much of the hormone dopamine in the brain or conversely because there is an high abnormality high number of dopamine receptors in the brain which could cause the symptoms of schizophrenia. (Grilly 2000).
Brain dysfunctions: Researchers who conduct a study using brain imaging techniques have found that many people diagnosed with schizophrenia have enlarged ventricles. On the average 15% larger than normal. A number of psychologists believe that increase in the size of these ventricles is what leads to schizophrenia (Kato, Y, 2011).
Viral infection resulting in brain abnormalities is suggested to be the cause of schizophrenia by some researchers. According to (Karayiorgou, M,, 2010). Contracting disease like flu or syphilis in the womb may lead to developing schizophrenia in later life. For example people give birth to more schizophrenia in the winter when the weather temperature is at zero or below zero degrees.
Kanahara, N, (2015) posits that Psychotic syndromes can be understood as disorders of adaptation to social context. Although heritability is often emphasized, onset is associated with environmental factors such as early life adversity,growing up in an urban environment, minority group position and cannabis use, suggesting that exposure may have an impact on the developing 'social' brain during sensitive periods. Therefore heritability, as an
index of genetic influence, may be of limited explanatory power unless viewed in the context of interaction with social effects. (Van Os, Jim, U Maastricht, 2009) Childhood abuse has been implicated as an environmental factor that increases the risk for developing schizophrenia. A study found that abuse may be a risk factor for schizophrenia in women, but not men. Violence against women is a major public health problem. Women with a diagnosis of schizophrenia suffer higher rates of violence compared with women without mental illnesses. Rice, E, 2006).
In conclusion, a lot of evidence support a strong genetic components responsible for the basis of schizophrenia. No single cause of the disorder has yet been identified. In this essay we would support the Diathesis–stress model as available evidence suggest a complex interplay of genetic and environmental factors.
References
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Eyler, L., Vuoksimaa, E., Panizzon, M., Fennema-Notestine, C., Neale, M., & Chen, C. et al. (2014). Conceptual and Data-based Investigation of Genetic Influences and Brain Asymmetry: A Twin Study of Multiple Structural Phenotypes. Journal of Cognitive Neuroscience, 26(5), 1100-1117. http://dx.doi.org/10.1162/jocn_a_00531
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Klahr, A. & Burt, S. (2014). Elucidating the etiology of individual differences in parenting: A meta-analysis of behavioral genetic research. Psychological Bulletin, 140(2), 544-586. http://dx.doi.org/10.1037/a0034205
Rice, E. (2006). SCHIZOPHRENIA AND VIOLENCE: THE PERSPECTIVE OF WOMEN. Issues in Mental Health Nursing, 27(9), 961-983. http://dx.doi.org/10.1080/01612840600899840
Seglem, K., Waaktaar, T., Ask, H., & Torgersen, S. (2015). Genetic and Environmental Influences on Adolescents’ Smoking Involvement: A Multi-informant Twin Study. Behav Genet, 45(2), 171-180. http://dx.doi.org/10.1007/s10519-015-9706-x
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Van Os, J. & McGuffin, P. (2003). Can the social environment cause schizophrenia? The British Journal of Psychiatry, 182(4), 291-292. http://dx.doi.org/10.1192/bjp.182.4.291
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