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Explain how twin and adoption studies attempt to distinguish genetic and environmental factors underlying the onset of schizophrenia within families. Review the studies and discuss two limitations of this.

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Introduction

Psychology Essay Explain how twin and adoption studies attempt to distinguish genetic and environmental factors underlying the onset of schizophrenia within families. Review the studies and discuss two limitations of this. Schizophrenia is the label applied to a group of disorders characterised by severe personality disorganisation, distortion of reality, and an inability to function in daily life. Symptoms are mainly disturbances of thought processes, but also extend to disturbances of emotion and behaviour. There are two symptom categories - acute schizophrenia characterised by positive symptoms, such as hallucinations and delusions; and chronic schizophrenia, characterised by negative symptoms such as apathy and withdrawal. However, DSM-IV has now moved away from these definitions and classified schizophrenia into three main sub-types: paranoid, disorganised and catatonic. Understanding Schizophrenia More research has, probably, been devoted to trying to understand the nature of schizophrenia than any other mental disorder. Somatogenic approaches have focused on the role of genetic mechanisms influencing the propensity to develop schizophrenia, while psychogenic approaches emphasise the effect of adverse childhood experiences, particularly abnormalities in family interaction in the aetiology of the disorder. Twin studies Twin studies offer a powerful method of disentangling the effects of genetic and environmental factors underlying the onset of schizophrenia within families. ...read more.

Middle

The largest study to use the adoptees family design was the Danish adoption study of schizophrenia (Kety, 1983). This found significantly increased risks of developing DSM-III schizophrenia among biological relatives of suffers than among relatives of the control group. However, there was no increased risk among adopted relatives of affected vs. control (Kety, 1983, Kendler et al, 1984). The Finish adoption study of schizophrenia (Tienari et al, 1994) confirmed the genetic contribution in schizophrenia;84% of the adopted offspring with schizophrenia developed a non-affective psychotic disorder, compared with only 0.5% of the adopted offspring of control groups (Tienari et al, 1994). However, a gene-environment interaction also emerged in the study (Wahlberg et al, 1997). When the adoptees were tested for schizophrenia at the mean age of 21, only those adoptees whose biological mother had, had schizophrenia and whose adoptive parents showed high level of communication deviance displayed schizophrenia. This was not observed among adoptees who had only a biological mother with schizophrenia or adoptive parents with a high level of communication deviance (Wahlberg et al, 1997). Adoption studies confirm the importance of genetic factors in the aetiology of schizophrenia - the Finish adoptive study has provided evidence for gene-environment interaction in the development of schizophrenia. ...read more.

Conclusion

Archives of General Psychiatry, 47:622-632. Cited in Gleitman, H, Fridlund, A.J. and Reisbery, D. (1998), Psychology, Norton. Ÿ Cardno et al (1999). Cited in Long, P.W. (M.D.) Internet Mental Health (www.mentalhealth.com) Ÿ Gottesman, I.I., Shields, J. (1982) Schizophrenia: The Epigenetic Puzzle. New York: Cambridge University Press. Cited in Gleitman, H, Fridlund, A.J. and Reisbery, D. (1998), Psychology, Norton. Ÿ Jones, R.E. (1983) Hospital Community Psychiatry, 34:807-811. Cited in Gleitman, H, Fridlund, A.J. and Reisbery, D. (1998), Psychology, Norton. Ÿ Kendler, K.S. and Gruenberg, A.M. (1984) Archives of General Psychiatry, 41:555-564. Cited in Gleitman, H, Fridlund, A.J. and Reisbery, D. (1998), Psychology, Norton. Ÿ Kety, S.S. (1983) Journal of American Psychiatry, 140:720-727. Cited in Gleitman, H, Fridlund, A.J. and Reisbery, D. (1998), Psychology, Norton. Ÿ Kringlen and Cramer, D. (1989). Cited in Long, P.W. (M.D.) Internet Mental Health (www.mentalhealth.com). Ÿ Makikyro et al (1998). Cited in Long, P.W. (M.D.) Internet Mental Health (www.mentalhealth.com) Ÿ Myhrman et al (1996). Cited in The Medical Post (1996) Maclean Hunter Publishing Ltd. Ÿ Ottman (1996). Cited in The Medical Post (1996) Maclean Hunter Publishing Ltd. Ÿ Tienari et al (1994) The Finnish Adoption Study Of Schizophrenia. Cited in Gross, R and McIlveen (1998) Psychology: A New Introduction, Hodder & Stoughton. Ÿ Wahlberg et al (1997). Cited in Long P.W. (M.D.) Internet Mental Health (www.mentalhealth.com) Also used www.schizophrenia.co.uk ...read more.

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In this well-researched account of the contribution made by genes and the environment to the development of schizophrenia, the writer shows clearly how MZ and DZ twin studies have aided our understanding of the role played by these underlying factors. This is an eloquent piece of scientific writing which wastes few words and relies on a wide range of studies carried out in the latter part of the 20th century. If there is any weakness in the essay, it is that the contribution made to the subject by 21st century DNA sequencing technology has been omitted (e.g. Singh and O'Reilly), but overall, this is an impressive piece of writing given the very small word limit.

Marked by teacher Ross Robertson 09/04/2013

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