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Mental illnesses - psychiatric problems

Clinical types

The term mental illness encompasses several different disorders including schizophrenia, depression (depressive illness), manic-depressive disorder, etc. The causes of these diseases are currently unknown, but they are probably varied and diverse.

Depressive illness affects 2% - 3% of the general population. It can be unipolar - i.e. the patient will suffer only from depression - or it can be bipolar, i.e. it is associated with mania and the condition is then called manic-depression. There is a clear genetic effect that can be deduced from the fact that if one identical twin suffers from depression, the other has a 50% risk of also being affected. This is compared to only 17% for non-identical twins. Untreated, there is a 20% risk for suicide. Women are more prone to suffer from these diseases.

Schizophrenia affects 1% of the general population. The severity varies in different patients, but all require treatment and periodic hospitalization. Untreated, patients will behave in an increasingly bizarre manner and may become dangerous. There is a real risk that such patients will pose a danger to other people (leading to their committing murder), to themselves (leading to their committing suicide), or both.

Clinical signs

Depressive illness and manic-depressive disorder manifest as emotional disorders of different degrees of severity. The causes are currently unknown, but are probably varied and diverse.

Schizophrenia, a psychosis, is characterized by hallucinations where the patient hears voices, or more rarely sees visions or senses odors, which are not real and exist only in his mind as a result of the illness, and delusions, which are a distorted perception of reality and sometimes involve paranoid delusions (paranoia), where the patient is convinced that someone is trying to kill him or poison him, or that other people can read his thoughts, etc.

Inheritance pattern

The pattern of inheritance is still not clear, but there are undoubtedly hereditary factors. Transmission appears to be multifactorial, i.e. a number of genes, some of which are situated on autosomal chromosomes and some on the X chromosome, in conjunction with environmental conditions, determine whether a particular person will develop a mental illness. The more patients there are in a family, the earlier the age of onset, the more severe the disease, and the more closely related the person is to a patient, the greater the genetic predisposition and risk for developing a mental illness and for transmitting it to offspring. Depression and manic-depressive disorder are more likely to be hereditary.


In depression, about 50%.

Associated features that can be demonstrated by imagery

Usually there are no defects that can be identified by ultrasound examination during pregnancy.

What is the risk that other relatives (or a fetus) will have the same condition? According to the degree of the relationship to a known patient in the family:

Degree of relationship to subject (or fetus) Schizophrenia or an undefined mental illness Depression or manic depressive disorder
No affected relative (normal risk in population) 1% 2% - 3%
Affected sibling 9% 13%
Affected parent 13% 15%
Affected sibling and parent 15% 20%
Both parents affected 45% 50%
Affected sibling and second-degree relative (uncle, grandparent, etc.) 3% 5%
Affected identical twin 40% 70%
Affected non-identical twin 10% 20%
Affected third-degree relative (cousin, great uncle, etc.) 1% - 2% 2% - 3%

Molecular genetic information

The genes for the diseases

Definitive genes have not yet been found, but there are a number of loci in the genome that are associated with a genetic tendency for mental disorders.


Genes have been examined in a number of chromosomes. There are probably a number of genes that have a role in the causation of the diseases, but until the picture is clearer, it is not practical to examine families with these disorders. The regions in the genome that might contain genes contributing to the development of mental disorders include 11p, Xp28, 5q, 9q34, and chromosomes 13, 15, and 18.

Genetic testing

Diagnostic testing

There are to date no clinical genetic tests available. Only in families with multiple cases is it possible to carry out investigations that may lead to the possibility of performing practical tests in some families in the future, initially by indirect tests (linkage analysis), and in the more distant future, once the gene itself has been found, by identifying the mutation or mutations. This will be done in cooperation with a genetic institute. See information sheet: Indirect testing for genetic markers in a family that has one or several patients - when there are a number of different genes that can each cause the disease - the gene, or most of the genes not having been located / identified / mapped - multifactorial diseases.

Carrier testing

This cannot usually be performed. See above under diagnostic testing.

Fetal testing

This cannot usually be performed. See above under diagnostic testing.
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