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Psycology » Psychiatry and psychotherapy » Biological bases of mental pathology » Genetics of mental illness

  1. Etiology and pathogenesis of mental disorders
  2. Genetics of mental illness
  3. Biochemistry psychoses

On the role of degeneration first spoke quite clearly B. Morel (1857). He led the clinical evidence of accumulation in different families degenerate stigmata of degeneration, so that in the third and fourth generations are born already mentally ill children, exhibiting, for example, signs of dementia praecox (premature dementia). Since the second half of the XX century the study of the role of heredity in the origin of psychosis is becoming increasingly important. Clinical experience with the development of genetics as a precise science became supported by conclusive information on violations of the structure of certain genes that are part of a set of human chromosomes. However, a direct genetic link rigid "breakdowns" with the emergence of mental disorders has been established only for a small number of mental illnesses. These currently include such as Huntington's chorea (the presence of the abnormal gene on the short arm of chromosome 4), a set of differentiated oligophrenia with distinct clinical and genetic diagnosis. This group includes phenylketonuria (autosomal dominant inheritance), Down syndrome (trisomy of chromosome XXI), disease Klinefelter syndrome (XXY or XXXY), disease Martin - Bell (with fragile syndrome on chromosome 10), a syndrome of "cat's cry" (the missing piece fifth pair of chromosomes), XYY syndrome with symptoms of mental retardation and aggressive behavior in men.

The involvement of several genes (their pathology) recently demonstrated against Alzheimer's disease. Damage to genes localized in chromosomes 1, 14, 21 leads to the emergence of early atrophic dementia amyloid deposition in the brain structures and neuronal death. A defect of a specific gene in the chromosome defines the later occurrence of 19 cases of sporadic Alzheimer's disease. In most endogenous mental illness (schizophrenia, epilepsy, manic-depressive psychosis - TIR) inherited by a particular diathesis, predisposition. Manifestation of the pathological process in this often provoked by psychogenic somatogenically. For example, changes in schizophrenia are a number of genes - such as NRG (8r21-22), DTNBI (6r22), G72 (locus 13q34 and 12q24), etc. Furthermore, as a probable source of the genes linked with mental pathologies treated different alleles of genes of glutamate receptors.

One of the earliest methods of genetic testing is considered the genealogical method, which consists in the analysis of pedigree, starting with the patient (proband). The important role of genetic factors in the development of psychosis in this case indicates an increase in the frequency of pathological signs in the immediate family of the proband and decrease its frequency with distant relatives. Of great importance are population-based studies, particularly international multicenter.

Twin method can more accurately judge the extent of the contribution of genetic and environmental factors in the etiology of psychosis. Assumed that concordance reflects the contribution of genetic factors in the occurrence of disease in humans, and, conversely, discordance between identical twins is determined by environmental factors. ME Vartanian (1983) resulted in generalized (averaged) data on the concordance of identical twins (OB) and fraternal twins (DB) for schizophrenia, TIR, epilepsy (Table 1).

Table 1. A summary of the concordance of identical and fraternal twins for a number of diseases,%

Gemini Schizophrenia CarnetEpilepsy OB445648DB131610

As seen from Table. 1, or at one of the diseases studied endogenous concordance in pairs ABOUT reaches 100%. Interpretation of the data geminate concordance faces several challenges. For example, according to psychologists, we can not exclude "mutual psychic induction", which is much more pronounced in the OB than DB. It is known that OB more eager to mutual imitation than DB. This explains the difficulty is accurately determining the contribution of genetic and environmental factors in the endogenous psychoses. In this respect, the methods developed to help family and the twin analysis (VM Gindilis et al, 1978).

The most notable achievement of recent times is considered a complete study of the human genome, which made it possible to create a new field in psychiatry - Molecular Psychiatry with molecular genetic studies (DNA Diagnostics). If used, for example, psychiatrists could be difficult clinical differences between Huntington's disease and catatonic schizophrenia due to individual preferences and differences schools researchers now possible accurate diagnosis with Huntington's chorea EVIDENCE defeat a number of loci on the short arm of chromosome 4.

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