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Psychiatry_ A Very Short Introd - Burns, Tom.rtf
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14. Mri scanner: the first really detailed visualization of the brain’s structure

Have these imaging techniques changed psychiatry yet? They have certainly increased knowledge and helped us understand the biochemical systems in the brain associated with disorders, and this has improved drug research. There are, as yet, no major advances in clinical practice as a direct result. Some early experiments are under way to transplant brain cells in Parkinson’s disease into areas where activity has been demonstrated to be deficient. There has even been a trial of inserting minuscule ‘batteries’ into the brains of some people with chronic depression to see if they stimulate an increased release of transmitter substances and alleviate the depression.

 

15. A series of brain pictures from a single mri scan. Each picture is a ‘slice’ through the brain structure, from which a 3d image can be constructed

This is a long way from the ‘Cyborg’ fantasy of so many films where small computer chips are inserted into the brain and control behaviour. There is a noticeable reluctance among neuroscientists to develop brain interventions for mental illnesses. Interfering directly with an individual’s consciousness and taking it out of their control generates strong resistance in scientists, as in the rest of us. This is in contrast, however, to surgery and cell transplantation in brain diseases such as Parkinson’s disease, which do not have the same implications for selfhood.

The human genome and genetic research

  Ever since Crick and Watson clarified the double helix structure of DNA in 1953 genetic research has been in overdrive. Genetics used to be the territory of plant and animal breeders applying Mendel’s laws, and medical researchers tracking familial diseases such as haemophilia and Huntington’s disease. Now it has blossomed into a programme which has mapped the very chromosomes and genes themselves. Previously geneticists could only inform patients about their statistical chances of passing on disorders. Now they can know for certain in some cases if the patient is carrying a disorder and even (as in the case of Huntington’s disease, a rare distressing disorder with both psychiatric and movement manifestations) predict if an at-risk individual will develop it years in the future.

  Not many psychiatric disorders, however, have simple ‘Mendelian’ genetic patterns where half (dominant) or a quarter (recessive) of the offspring are destined to have the illness. Most of the major disorders (e.g. schizophrenia, bipolar disorder) do run in families and have an undeniable genetic component but there are almost certainly several genes involved and they have been very difficult to identify. There have been many false dawns. Currently the likeliest candidate is Neuregulin 1 (a gene identified in schizophrenia families in Iceland and the West of Scotland). However this gene is more widespread than is schizophrenia – possibly up to 30 per cent of the population may carry it. Neuregulin 1 appears to be necessary for developing schizophrenia, but not sufficient. Some life experiences (or perhaps combination with other genes) are also required. So an interaction between nature and nurture is indicated. This may explain why the issue has been so resistant to the ‘either—or’ solutions of the past. It holds out hope that even in those with the genes for the disorder it may be possible to prevent schizophrenia developing.

  While genetic research has yet to have a major clinical impact, in practice it has certainly stirred up thinking. What level of risk are we willing to take if we know that we have a higher than average chance of our child developing schizophrenia or depression? Would it be ethically acceptable to start screening for these disorders once the genes have been confidently identified? What if we were also able to identify genes for being clever – would it be OK to screen for that? Screening implies selection. It is usually only done if the individual wants to know whether to start or continue with a pregnancy.

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