Most mental illnesses arise without family history.

Summary: A massive Danish study shows that most mental illnesses, such as schizophrenia, bipolar disorder and depression, occur in people without family history close to the condition. Analyzing data from more than 3 million people, researchers found that, although inheritance increases risk, most diagnosed people do not have affected relatives.

This challenges stigma and clarifies that mental disorders arise from complex genetic and environmental factors. The findings highlight the need for personalized approaches and population level for mental health.

Key facts:

Rare family history: 89% of people with schizophrenia have no close relative with the condition.

Source: University of Aarhus

It is a common belief that mental illness “extends in families.” And although it is true that inheritance plays a role, in reality, the vast majority of cases, such as schizophrenia, bipolar disorder, depression and borderline personality disorder, occur in people without known hereditary predisposition.

This is the conclusion of a new important study conducted by researchers from the Danish Research Center based on records, University of Aarhus, recently published in the scientific journal Lancet Psychiatry.

The study is based on data from more than 3 million Danes, and researchers expect it to help relieve concerns and reduce stigma.

“In general, people are more concerned about what they see among close relatives. Very few fear that they will develop schizophrenia unless they have a relative with the condition. But this study clearly shows that we all have the risk of developing mental illnesses,” says Professor Carsten Bøcker Pedersen, who co -authorized the study with the teacher who the aberb.

“Eighty -nine percent of people diagnosed with schizophrenia have no history of close relatives. Therefore, it is far from being something that only occurs in affected families,” he adds.

A similar pattern with depression is observed: 60% of people who experience depression do not have relatives with the disorder.

What does my mother’s disease mean to me?

The study raises an important question: if most mental illnesses occur in people without a relative with the same condition, how do they arise?

Researchers cannot give an accurate answer.

“Mental disorders are hereditary, but they are also highly polygenic. They often result from many small genetic variations, not a single” disease gene. “In addition, the environment and chance also play a role,” explains Professor Esben Agerbo.

“But the study is innovative because it describes the absolute risk: how many out of every 100 people will develop a specific mental disorder in their life. This functions as an atlas, helping people to understand, for example, the statistical involvement of having a mother with a mental illness,” he says.

Researchers expect data to help kill the narrative for families affected by highly inherited conditions such as schizophrenia.

“If your father or sister has schizophrenia, it does not mean that it will necessarily develop it. In fact, the study shows that 92% of people with a first -degree relative with schizophrenia do not develop the disorder themselves,” says Carsten Bøcker Pedersen.

So, although the study supports that inheritance is a factor, it also makes it clear that inheritance is unpredictable and complex, he adds:

“If he has a father or brother who has had depression, his risk of developing depression is around 15%, while his risk is less than 5% if he has no close relatives with the condition. But that also means that he still has an 85% chance of not developing the disease, even if he appears in his immediate family. It is an important message.”

Cavando in the old records of the Church

The researchers used Danish national records to link people and their mental health diagnoses in generations. The study is based on the Civil Registry System, the Multigeneration Registry, the Danish Psychiatric Central Research Registry and the National Registry of Patients.

All those diagnosed in psychiatric care between January 1970 and December 2021 are included in the study, but all data are pseudonymized, which means that researchers never accessed personal identification information.

Carsten Bøcker Pedersen and Esben Agerbo are key figures behind the multigeneration record, which are developing in collaboration with the Danish national archives. The registration links the data of the family relationship of the civil registration system with historical information of the Church records, tracing the Danish family links until 1920.

The multigeneration record provides a powerful basis for more studies on how inheritance and family structure influence health in Denmark, such as the development of mental illnesses.

“This study points to the need for a double track approach to address mental illness. A track implies a personalized medicine, considering individual genetics and the environment. The other involves measures throughout the population, such as reducing social stressors, reducing alcohol consumption and promoting mental well -being,” says Esben Ager.

“Both are essential if we want to prevent and understand mental illness, in both people with relatives with mental illnesses and most for whom the disease arises without family history,” he concludes.

About research

The study is a prospective cohort study. Investigated disorders: substance abuse, cannabis abuse, alcohol abuse, schizophrenia and related disorders, schizo -affective psychosis, affective disorders, bipolar disorder, depression, personality disorders, limit personality disorder and antisocial personality disorder. Financing: Novo Nordisk Foundation

On this mental health and neuroscience research news

Author: Vibe NOORDE MA
Source: University of Aarhus
CONTACT: VIBE NOORDELOS – UNIVERSIDAD DE AARHUS
Image: The image is accredited to Neuroscience News

Original research: open access.
“Absolute and relative risks of mental disorders in families: a Danish study based on records” by Carsten Bøcker Pedersen et al. Lancet psychiatry

Abstract

Absolute and relative risks of mental disorders in families: a Danish study based on records

Background

Relative risk estimates of family aggregation of many types of mental disorders are available, but absolute risk estimates of family aggregation of mental disorders remain scarce.

The proportion of individuals who develop a mental disorder in the absence of the same disorder in a relative (non -family cases) has not been examined. Our goal was to create comprehensive risk estimates of the family aggregation of mental disorders.

Methods

In this study of prospective cohort, we follow people of Danish origin between January 1, 1970 and December 31, 2021. We use Danish records based on the population to link people and their mental health through extended family pedigis.

These records include the Danish Civil Registry System, the Danish Multi -Generation Generation Registry, the Danish Psychiatric Central Research Registry and the National Danish Patients Registry. The mental disorders investigated were substance consumption disorder, cannabis consumption disorder, alcohol consumption disorder, schizophrenia and related disorders, schizophrenia, schizoecofecto disorder, mood disorders, bipolar disorder, unique and recurrent depressive disorders (depression), personality disorder, limit disorder of personality and disorder of the antisocial personality.

We estimate the risk of life (risk up to 60 years), specific absolute risk of the age and relative risk for each mental disorder and type of affected relative (eg we calculate the estimates of inheritability and the proportion of non -family cases. We involve people with lived experience related in the design and implementation of the study.

Recommendations

A total of 3 048 583 individuals (1 486 132 (48 · 75%) females and 1 562 451 (51 · 25%) men) were followed for 80 425 971 person-year. People with a family member with a specific type of mental disorder had greater life risks and relating to developing the same type of mental disorder. Both life and relative risks were greater the closer to the affected kinship.

For Example, The Lifetime Risk of Depression was 15 · 48% (95% ci 15 · 31–15 · 65) in individuals with affected First-of Gree 4 · 68% (4 · 65–4 · 71) in uninfected individuals of first degree and second grade.

The inheritability of depression was 45 · 4% (95% IC 44 · 8–46 · 0) and the proportion of non -family cases constituted 60 · 0% (95% 59 · 8–60 · 2).

Interpretation

People with family members with a mental disorder face greater risks of the same disorder. From a population perspective, most mental disorders occur in individuals without affected close relatives, which highlights the need for prevention strategies that are directed to the entire population.

Funds

Novo Nordisk Foundation.

Translation

For the Danish translation of the summary, see section of complementary materials.