StemCell Therapy

While genetics can play a significant role, the picture is much bigger.

If a man has type 1 diabetes, there is a 1 in 17 chance that his child may also get it. The oddsreduceto 1 in 25 if the woman has it, and the child is born before she is 25. Type 2 diabetes has astronger linkto genetics than type 1. Genes also playsome rolein conditions like hypertension and heart ailments. And just like these illnesses, mental health issues also have some degree of heritability. However, the stigma associated with mental health makes the heredity and its implications more difficult to navigate.

Recently, actor Rhea Chakraborty said in an interview that late actor Sushant Singh Rajputs mother had lived with depression. Sushant, who was found dead in his Mumbai apartment in June, reportedly by suicide, was living with mental health issues as well. In the aftermath of the incident, there have been discussions on how Sushants mental health struggles could have been hereditary. But what do we really know about the link between genes and psychiatric disorders?

There have been numerous studies in the past and ongoing to study these links. Astudyby Consortium on the Genetics of Schizophreniapinned the heredity of schizophrenia at 31% to 44% in nuclear and extended families respectively. When bipolar disorder was included in this, the heritability increased to 37% in nuclear families. And when it came to depression, in the same study, the heritability dropped to 34% in nuclear families and 20% in extended families.

Otherstudiessay that the chances of a person developing schizophrenia if a biological parent has the condition are 13 in 100, and for bipolar disorder, its around 30 in 100. Studies have also been done on identical twins, and have found that if one sibling has schizophrenia, theres a 40-50% chance the other will develop it, because they share the same genetic makeup. Alzheimers dementia is another disease known forhigh heritability.

Dr Sanjeev Jain, officer-in-charge of the Molecular Genetics laboratory and a professor of Psychiatry at the National Institute of Mental Health Sciences, (NIMHANS) in Bengaluru, points out that most things including looks are inherited from biological parents. Mental illness is not very different that way. The only thing is that we have not been able to figure out the precise mechanism by which the causal genes get triggered. Besides, people tend to forget that if there is a 10% chance you will develop a mental health condition due to heredity, there is also a 90% chance that you wont. Till date, we have not been able to predict mental illness, because it does not only depend on the genes, he says.

Dr Sanjeev has been involved in many research and molecular diagnostics projects on neuropsychiatric disorders including Obsessive Compulsive Disorder (OCD), alcoholism, dementia and schizophrenia for several years. He, along with his colleague, Dr Biju Viswanath, Associate Professor of Psychiatry at NIMHANS, are conducting a study Accelerator program for Discovery in Brain disorders using Stem cells(ADBS) using clinicalinvestigations, modern human genetics, and stem cell technology" at NIMHANS. The study has been on since 2016.

Dr Biju says that while there's a 60-70% risk of developing a psychiatric illness contributedby genes, there are several other factors that cannot be discounted. Dr Hema Tharoor, a psychiatrist associated with Chennai-based Schizophrenia Research Foundation (SCARF), points out that it is ultimately the gene-environment interaction that determines whether a person could develop a mental health issue.

There are studies, for instance, that look at siblings wherein one parent had schizophrenia but only one child developed it, and the other two did not. And its not just sociologicalfactors that playa major role in determining ones mental health, it is also things like the antenatal and postnatal care of the mother, low birth weight, infections during pregnancy, that determine the risk of developing these disorders in the persons life too, she explains.

One 2011study, for instance, found that the risk for schizophrenia increased with certain obstetric complications, famines, migrant status, and advanced paternal age. Severe pregnancy and perinatal complications also accounted for environmental risks.

Further, Dr Sanjeev points out, its very difficult to separate genetics and culture. At any point of time, you are expressing only a third of your genes. Different genes will express themselves at different points of time. Only when that expression crosses a threshold does it become a disease.

Besides, we simply dont know all the genes that contribute to the risk of developing a psychiatric disorder or illness. In the case of Alzheimers, studies haveimplicated215 potential causative genes. However, the study by the Psychiatric Genomics Consortium said that these only explain a small proportion of genetic variance, meaning that yet undiscovered genes remain. This is the case with other mental health issues and psychiatric disorders as well.

Even so, experts say it is not necessary that everyone who carries the risk increasing genes will develop the illness its just that the genes could increase the susceptibility of an individual to getting it, and the trigger threshold for the onset could be lower. So, for instance, if someone is at a higher risk to develop OCD due to heredity, and they have also been through trauma in childhood, it could cause early onset. But its also possible that they do not develop it at all, depending on the other factors, Dr Biju says.

Several illnesses like breast cancer and leukaemia have been proven to have a high heredity factor. In some cases, gene therapies have been devised to correct or replace certain genes that could cause some illnesses. However, this is not the case with mental illnesses. The study of the brain and mind is harder because you cant just do a biopsy of the brain, says Dr Sanjeev. However, the advantage to figuring out the genomic links to mental health is that once we know the cause, we can have better drugs to treat them. Most of the ones we use now are decades old.

Dr Biju similarly says, As a doctor, you want to see your patients health improve. Say, 50% of the patients get better with psychiatric medication, but the remaining struggle. But we do not know why the medication is not working. So, if we can understand how the illness or disorder originates by identifying the genes, you can identify the mechanisms; and then we can move to more effectivetreatments.

Dr Abhishek ML, a psychiatrist and a research faculty at Bengaluru-based Indian Institute of Science (IISc), says that another hope in studying the heredity of mental health issues is early preventability. Dr Hema adds, If we can establish the endophenotypes (the neurobehavioral traits that quantify genetic susceptibility to developing a psychiatric disorder), then it becomes a preventable risk. Special care can be taken then in, say, antenatal or postnatal care.

However, Dr Abhishek cautions that this sort of technology should be accompanied by destigmatising mental health, lest it leads to profiling of persons living with certain mental health conditions and impinging of their rights.

Read more:
Understanding mental health and its heredity: What experts know so far - The News Minute

This entry was posted on September 6, 2020 at 12:00 pm and is filed under Genetics. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |