What is the likely role of genetic transmission in schizophrenia?
Schizophrenia has been defined as a “significant loss of contact with reality, often referred to as psychosis” (Butcher, Mineka, Hooley & Carson 2004 p.458). Although schizophrenia is termed as one illness, it is more likely that it is a combination of disorders with “a variety of etiologies, courses and outcomes’ (American Psychiatric Association 1997 p.49). The symptoms of the illness include hearing voices and a conviction that external forces are interacting on the person. An overall disillusionment with life results from these symptoms and tends to lead to detrimental effects on everyday functioning. The causes of this disorder are unclear, however it has been shown to be a combination of environmental and genetic factors, the two interacting to cause the onset of schizophrenia.
The discussion of nature and nurture in any disorder is an important one, and just as relevant with schizophrenia. A meta analysis collaborated by Gottesman (1991) showed that there was over a 45% risk of identical twins both suffering schizophrenia if one already suffers from the disease (sharing 100% of the same genes). Fraternal twins (sharing 50% of the same genes) had a 20% chance of both suffering from the disease, this steadily decreases as the percentage of genes shared reduces. This is good evidence for a genetic basis to schizophrenia, but does not explain exactly why schizophrenia occurs, as if schizophrenia was completely genetically based, there would be 100% concordance rates in identical twins. We can assume that if a certain percentage is accounted for through genes, there will be other factors that influence the onset of schizophrenia.
Other factors that may influence the onset of schizophrenia may be the environment that a person lives in. It could be said that due to the genetic factor involved in genes, different environments could speed up or slow down the onset of schizophrenia dependant on the stimuli that a person comes into contact with. Another factor may be problems in birth and childhood, which could lead to abnormalities in adulthood, resulting in more predispositions to the disorder than someone without these disadvantages.
Schizophrenia may be detectable from a very early age, giving support for a genetic basis for the illness, as long-term environmental effects may not have had enough time to seriously affect the sufferer. Research by Walker in 1993 examined family home movies of 32 children who later developed schizophrenia. The examiners watching the videos were unaware that the children later developed an illness, and were asked to comment on the children’s behavior. It was found that there were significant abnormalities in emotional and motor activities in the schizophrenia sufferers than their relative siblings. This may be some evidence for genetic basis for schizophrenia, due to there being signs of the disease from an early age. It may be overstating the evidence to suggest that schizophrenia may be detectable just from behavior, but a general sense that a person may develop a disorder in adulthood could be concluded from any unusual childhood activity. The reasons for this unusual behavior may result from earlier problems within the family or a genetic predisposition to illness.
Heston (1966) studied children whose mothers had been hospitalised due to schizophrenia. These children had been looked after by other family members or put into foster homes. It was found that these children had a 16% chance of becoming schizophrenic, compared to a 1% chance of a random sample of similar children in the same area. It was also found that these children were significantly more likely to become mentally retarded, neurotic and psychopathic. This is evidence for the claim that schizophrenia comes from a multitude of other abnormalities, as well as that there may be a genetic cause that carries over generations. The reasons for the...
Please join StudyMode to read the full document