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Genetic Predisposition on the Inheritance of Mental Illnesses

A girl with schizophrenia covering her ears as not to hear her alter ego / Photo by Shutterstock

 

Discoveries involving mental health is still a long but attainable journey ahead. Much has been made with the progression of various mental disorders and other chronic illnesses with the efforts of scientific research and technology advancements.

 

Insane, mad, and retarded

Hereditary situations with mental cases go back to ancient asylums where so-called “Madhouses” keep people with neurologic conditions and children with intellectual disabilities are examined by physicians.  

Gregor Mendel’s plant-breeding experiments raised eugenicists’ hopes that people inherit mental health or illness as systematically as peas inherit smooth or wrinkled skins. This simple experiment sparked the start of genetics and the secrets behind mutation.

German researchers then organized an unprecedented project to collect data on family traits of asylum patients, intellectually disabled students, and prisoners. Family pedigrees, for instance, remain part of research into the inheritance of mental disorders which again paved the way to more understanding on these conditions.

A genetic predisposition results from specific genetic variations that are often inherited from a parent. These genetic changes contribute to the development of a disease but do not directly cause it. Some people with a predisposing genetic variation will never get the disease while some might be able to acquire it, unfortunately.

The scientific analysis in the world of insanity and madness continues to mind boggle researchers as they explore data in a different setting. Slight genetic changes in mutation combined can increase the risk of accommodating diseases which are rarely attributed but could possibly be susceptible to the inheritance of mental illnesses.

Mental conditions such as schizophrenia, multiple personality disorder, and Alzheimer's contributed largely to the experimental aspects of genetic inheritance in search of treatment methods and likewise clinical trials of certain drugs.

Mutations can occur in different types. It could be a deletion, substitution, or even a duplication of certain genes which would end up badly in your standard definition of being ‘normal’.

Hereditary conditions may often lead to serious illnesses such as Huntington disease, where signs and symptoms do not occur until after a person has children, so the gene mutation can be passed on despite being harmful.    

 

 

The University of Georgia psychology professor Keith Campbell agrees with the underlying premise of inheritance. “In general, there are significant hereditary factors for mental conditions of all kinds,” he says.

While some of these diseases are acquired genetically through familial inheritance, several factors including lifestyle exist as it projects the risk of attaining the disease significantly.

Gene alterations commonly contribute to a variety of mental illness but in addition, these small-scale changes may, later on, lead to the underlying susceptibility to common diseases such as diabetes and cancer.

Current research is focused on identifying genetic changes that have a small effect on disease risk but are common in the general population.

In people with a genetic predisposition, the risk of disease can depend on multiple factors in addition to an identified genetic change. These include other genetic factors (sometimes called modifiers) as well as lifestyle and environmental factors. Diseases that are caused by a combination of factors are described as multifactorial. Although a person's genetic makeup cannot be altered, some lifestyle and environmental modifications (such as having more frequent disease screenings and maintaining a healthy weight) may be able to reduce disease risk in people with a genetic predisposition.

 

Alzheimer's link with Down Syndrome in mice

Scientists are a step closer to understanding which genes are responsible for early-onset Alzheimer's disease in people with Down syndrome, thanks to a study led by researchers at the Francis Crick Institute along with UCL collaborators.

Around 1 in 800 people are born with Down syndrome, which arises in people carrying an extra copy of chromosome 21. By the time they reach their 60s, around two-thirds of those with Down syndrome will have early onset Alzheimer's.

The high rates of Alzheimer's in people with Down syndrome were previously thought to be caused by a particular gene on chromosome 21 called APP. Chromosome 21 contains 231 genes, but APP was the prime suspect because it produces amyloid precursor proteins. These are involved in generating amyloid beta proteins, which build up in the brain in Alzheimer's patients.

In this study, published in the journal Brain, researchers found that extra copies of other genes on chromosome 21 increase Alzheimer's-like brain pathology and cognitive impairments in a mouse model of Down syndrome.

Dr. Frances Wiseman, Senior Research Fellow at UCL, and first author of this study said: "We've shown for the first time that genes other than APP are playing a role in early-onset Alzheimer's disease in our model of Down Syndrome. Identifying what these genes are, and what pathways are involved in the earliest stages of neurodegeneration, could help us to one day intervene with these pathways to prevent the disease in people with Down syndrome."

Dr. Victor Tybulewicz, Group Leader at the Francis Crick Institute and co-senior author of the paper, said: "Down syndrome has historically been very difficult to model in a mouse because the genes that we have on chromosome 21 are spread across three different chromosomes in mice. Only after years of refining our mouse models can we study the earliest stages of Alzheimer's, and other diseases, in the context of Down syndrome."

 

Their findings could pave the way for future medicines to prevent the disease in these individuals, and provide insights into the mechanisms that cause dementia in the general population.

 

A young boy with down syndrome wearing a headphone / Photo by Getty Images

 

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