Psychiatry

     Psychiatric disorders are the most prevalent cause of chronic disabilities around the globe and many have been proven to be genetically inherited through family studies. A first-degree relative of a person with a mental illness is much more likely to develop a mental illness than the general population (some studies say ten times more), especially if the relative is an identical twin as they have the highest likelihood of having the gene.

     Schizophrenia, Bipolar Disorder (BPD) and Autism are the three mental disorders that have benefited mostly from the HGP in that they have had the most advanced research and the most results gained, due to the screening of the human genome for their potential candidate genes.

     Prior to the human genome sequencing, the number of possible genes that could cause one of these conditions was enormous but now that the HGP is completed, it has been screened using more advanced markers and the candidate genes have been greatly narrowed down to only a few.
     The HGP also allows investigators to see which of these possible genes is the most expressed in the brain by determining the mutated gene in individuals with the condition.
     Not only can this mutation be polymorphic (i.e. have more than one phenotype as a result, depending on its context), but the phenotype itself can also have more than one gene involved, which can make detection of the exact gene(s) very difficult.
     The HGP allows much quicker scanning of the genes that may be involved therefore the likelihood of misdiagnosis of the symptoms is significantly reduced. Instead of relying purely on symptoms, there is now genetic evidence to back up the case. For example, if a person is thought to be schizophrenic but does not have the chromosome 13 gene mutation, for example, in their genome then they may have another similar medical condition instead, such as BPD.

     However, these types of psychiatric disorders are often multifactorial (i.e. have many contributing factors in the equation) and so although someone may have the genotype for the disorder, it may not have been "triggered" by an environmental event in order to give a phenotype of a mental illness.
     To be even more complicated, a person may possess two (or more) mutated genes that each contribute to separate mental disorders but only one contributes to their phenotype. For example, a person has the mutated genes for both schizophrenia and BPD but only display symptoms for BPD. Since both schizophrenia and BPD symptoms are similar the person could then be misdiagnosed as schizophrenic... but since the allele for schizophrenia is present (but has not produced a phenotype) then it will be detected via genetic testing and therefore "confirm" the misdiagnosis as a schizophrenic. This may result in incorrect treatment for their mental illness. It is likely that this case is rare, but this is a letdown of having so many candidate genes.

     Although the HGP will contribute a great deal of genetic information to the field of psychiatry and allow more accurate diagnoses and also more targeted drug development, the environment still plays a large part in mental illnesses, therefore cannot be ignored in terms of what other methods can be used to decrease symptoms. Some non-medical methods, such as eliminating the environmental trigger, could significantly help to reduce the number of relapse episodes that occur.

 

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