Family aggregation, also known as familial aggregation, is the clustering of certain
traits, behaviours, or disorders within a given family. Family aggregation may arise because of
genetic or environmental similarities.
[Butcher, J., S. Mineka, and J. Hooley. Abnormal Psychology. 15. Boston: Pearson, 2010. Print.]
Schizophrenia
The data from the family aggregation studies have been extensively studied to determine the mode of inheritance of
schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...
. Studies to date have shown that when numerous families are studied, simple modes of inheritance are not statistically supported. The majority of studies analyzing for the mode of inheritance have concluded that a multifactorial threshold mode is most likely.
Cardiovascular problems
The most consistent and dramatic evidence of family influences on
cardiovascular disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
(CVD) is family aggregation of physiological factors. In several studies the parent-child and sibling-sibling correlations of
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
are approximately .24. Genetic determination of blood pressure is strong, but does not explain all of the variance.
Parkinson's disease
Familial
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
(PD) exists but is infrequent. Early investigations failed to show substantial family aggregation for PD.
See also
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Genetic disorder
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
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Genetic epidemiology
Genetic epidemiology is the study of the role of genetic factors in determining health and disease in families and in populations, and the interplay of such genetic factors with environmental factors. Genetic epidemiology seeks to derive a statist ...
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Family cancer syndrome
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Blue Fugates
The Fugates, a family living in the hills of Kentucky starting in the 19th century, were commonly known as the "Blue Fugates" or the "Blue People of Kentucky". They are known for being carriers of a genetic trait that led to the blood disorder ...
References
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Classical genetics