The studies for family studies where taken place when diagnosis was under a more liberal use of the term schizophrenia. Amphetamines are drugs which produce a state closely linked to paranoid schizophrenia.
This indicates that an interaction of genetics and environment is at work in determining human aggression. Further research to support this comes from Brunner, who found that in a large Dutch family where all the males had a mutant form of the MAOA gene, they all acted aggressively when angry or fearful, suggesting this low variant resulted in low levels of Serotonin which increased their aggressive responses.
Therefore this study provides strong support for the importance of genetic factors in the development of schizophrenia, as well as other psychiatric disorders.
Although the dopamine hypothesis has good scientific support based on PET scans and post mortems, it has ignored the complexity of the biochemistry of the brain. None of the controlled group was diagnosed with schizophrenia versus 5 of the 47 whose biological mother had schizophrenia.
Overall, the dopamine hypothesis suggests that schizophrenia is a result of high activity or high D2 receptors.
Also Mikaywa noticed that schizophrenia runs in the family, meaning there must be something other than environmental causes, causing the disorder. The gene called monoamine oxidase A MAOA produces an enzyme which regulates the metabolism of serotonin in the brain.
Clozapine blocks dopamine receptors making less dopamine available, this effect has been proven by PET scans, thus providing greater biological evidence that dopamine receptors are responsible for some of the symptoms.
However research by Tyler reported that drug treatments were not having any success, suggesting that other non-biological factors may be involved. This leads to the characteristic symptom of schizophrenia, such as anhedonia, flat affect and asociality. These interact with environmental stimuli to cause aggression which is an interactionist view.
The other biological explanation is The Dopamine Hypothesis. McGuffin et al argues this is because of the use of different diagnostic criteria, which may affect the validity of the results. Another study in support is the prospective study by Kety et al.
Research has also found that schizophrenia symptoms may have a genetic component. Evolutionary theorists argue that although schizophrenia is maladaptive it is closely related to leadership qualities such as artistic ability, and creativity.
Both family and twin studies face the problem of ignoring environmental impacts. Schizophrenia by behaviour is a phenotype, and is thus affected by the influence of genes and the environment. Cases et al found that mice genetically engineered to lack MAOA had a dramatically altered serotonin metabolism and as adults showed enhances aggression particularly during mating, suggesting that aggression is a direct result of MAOA deficiency rather than other genetic influences or psychosocial factors.
Similar to the Gottesman study two other studies showed higher concordance rates for MZ twins and lower in DZ twins however each had slightly different results. Further research to support this development comes from Moffitt et al who found in a longitudinal study on New Zealand males that those who had suffered abuse as a child and had the low MAOA variation were nine times more likely to display aggressive behaviour than those who had been abused but carried the high MAOA variant or those who had not been abused.
In genetic explanations of schizophrenia, adoption, family and twin studies are used. However research has also found that, as well as excess of dopamine, increase numbers of dopamine receptors can be the cause of schizophrenia. Recent research has suggested that genetic factors affect the hard wiring of the brain.
What Mikaywa studied was DNA from human families who were affected by schizophrenia and found that those with the disorder are more likely to have the defective gene: It is also difficult to establish cause and effect; is increase dopamine activity caused by schizophrenia or does it cause schizophrenia.
However a greater number of dopamine receptors are not responsible for all the symptoms; they only account for the positive symptoms. They release three neurotransmitters, the bulk of which is dopamine.
It seems aggressiveness is influenced by a variation in the MAOA gene which is sensitive to negative social experiences early in human development.
These traits may be adaptive in the time our evolutionary ancestors were in the process of evolution and therefore persisted into our genes.
However research has also found that schizophrenics have abnormally high D2 receptors. Genes also determine the synthesis of testosterone receptors, and how many and how sensitive such receptors are.
This is an important explanation because there is a debate as to the reason why the gene causing schizophrenia if one exists has not evolved out. These infants were separated from birth and raised by adoptive parents. However a limitation of this kind of research is that there are many qualitative and quantitative differences between mice and humans so making it difficult to generalise the findings of this kind of research directly to humans.
More essays like this: A strength of the low MAOA variation is that theoretically it may be possible to devise drug treatments for people with this variation to help control aggressive urges.Furthermore, the purely genetic basis of aggression is a limited explanation because it has proved elusive and it would be reductionist to argue this because it appears that numerous genes are involved.
Describe and evaluate biological explanations of OCD (10 marks) The biological approach as an explanation of OCD believes that the disorder is caused by a fault in our body, either through genes, hormones, the brain, or neurotransmitters, therefore suggesting that OCD is caused by our nature, rather than our upbringing.
Discuss genetic explanations of aggression (4+8 marks) Essay gene which has been linked to aggression is the gene coding for the production of monoamine oxidise A (MAOA). Brunner et al studied the men in a family with a tradition of violent men, they discovered that the gene responsible for producing the enzyme MAOA may be.
Genetic explanations for the Initiation of addictions. Heritability of addictions such as alcoholism and gambling can be studied through family and twin studies. The presumptions of twin and family studies are that if family members share similar behaviours, then the degree to which the behaviours are caused by genetic factors.
This essay aims to outline and compare the genetic, bio-chemical and environmental explanations for the cause of schizophrenia, as well as discussing the evidence for each explanation considered.
The genetic explanation for the cause of schizoph. Outline and evaluate one or more biological explanations of schizophrenia. In your evaluation you should refer to research evidence.
24 marks According to the genetic hypothesis, the more closely related the family member to the schizophrenic the greater their chance of developing the disorder.Download