Is depression hereditary?

Depression is an emotional disorder that affects more than 300 million people worldwide according to data from the WHO (World Health Organization), Spain is the fourth country in Europe in number of cases with two million people affected.

 What are its causes? Can it be transmitted from parents to children through genes? Is depression hereditary? In this post we answer these questions!

What is depression?

Depression is a mental illness that causes low mood, apathy and feelings of sadness, which generally affect the level of activity, thinking and behavior of people who suffer from it.

Sometimes, it is accompanied by negative feelings such as guilt, irritability and pessimism, as well as a decrease in concentration, appetite and libido. In the most serious cases, ideas of death or suicide may appear.

It is a pathology that does not affect both sexes equally. According to WHO data, of people with depression, 5.1% are women and 3.6% are men.

Causes of depression

Is depression a biological disorder or is it caused by external events? Actually, both concepts are valid, in endogenous depression there is a biological cause that motivates it and in exogenous depression there are factors that can cause it or at least ignite the fuse that causes the development of symptoms. 

Depression is generally produced by the interaction of various biological factors that converge to give rise to the symptoms associated with this pathology. 

Some of these factors are:

  • Biological differences : people with depression have certain physical changes in the brain, these kinds of differences are being studied and are not fully understood. 
  • Brain chemistry : neurotransmitters such as serotonin, dopamine or norepinephrine play an important role in brain communication, alterations in its functioning are related to depression and its treatment.
  • Hormones : Hormones can play an important role in depression, mainly in physiological states such as pregnancy, postpartum, menopause, thyroid problems, etc. where changes in hormone levels are important.
  • Genetic factors : Depression is more common in people who have close relatives who have it.
  • Psychosocial factors and personality : especially psychological defense mechanisms such as resilience can protect a person against depression and other emotional disorders.   

So is depression hereditary?

But is it the case of the condition that concerns us? that is, can depression also be inherited? 

The development of depression depends on genetic and environmental factors. Specifically, the heritability of this pathology is estimated at 40-50%. What does this mean? The concept of heritability refers to the percentage of the population with this disease whose causes are attributable to the variation in DNA between individuals , but it does not mean that the children of a person with depression will present it with a 40% probability, it is not! Right! This means that genetic inheritance explains 40% of the individual differences in presenting depression. Perhaps this sounds very technical, the important thing is thatthere is a genetic factor, this means that these genetic variations can be passed from parents to children and the risk for first degree relatives is greater, but it does not mean that they will develop the disorder. 

This also occurs in other mental illnesses, for example in schizophrenia, as we explain in detail in our article Causes of schizophrenia and heritability. 

The “threshold of susceptibility” in depression

Depression does not follow a classic pattern of Mendelian inheritance. Its transmission is explained with the “threshold of susceptibility” model. This means that environmental and genetic factors interact with each other to give an overall risk burden for depression. People who pass the “susceptibility threshold” will develop the disease.

What are the “depression genes”?

Various studies have been collecting the existing scientific evidence to determine the genes that have a determining effect on the development of depression, however, this task has not been very fruitful. 

There are some genes that seem to increase the risk of presenting the disease, but they always act globally with other genes and with environmental factors.

Some of these genes are SIRT1, LHPP , the genes related to serotonin and its receptors HTR2A, SLC6A4, 5HTT, the MDD1 gene or the MDD2 gene.

Types of depression

Not all depressions are the same, as there are different classes depending on their symptoms and development. In each of them the weight of the factors that cause it varies. 

Mainly we can distinguish the following types of depression:

  • Major depression: this type of depression has a predominant genetic component and, although there is also an environmental factor, it has much less weight. Major depression can recur and, in certain cases, appears to be somewhat seasonal.
  • Reactive depression : in this case, the opposite situation usually occurs: the genetic contribution exists, but it is less, and the disease is usually caused by poor adaptation to external stressful situations that the patient cannot cope satisfactorily.
  • Dysthymia: in this type of depression the symptoms are usually milder than in the previous two, and have a chronic evolution. It usually develops slowly, but the presence of symptoms is constant. It seems to be related to personality and exposure to prolonged stress. 
  • Masked depression: in this case the patient does not present the typical symptoms of depression, but rather somatizes the disease in physical alterations (somatization) or in behavioral changes.

Resilience, a resource to manage depression 

Surely the term resilience sounds familiar to you, because lately there has been a lot of talk about this ability that human beings have to adapt positively to adverse situations. Resilient people have a protective factor for mental and even physical health, since they have a resource to get ahead in difficult situations. But what are the factors that make a person resilient? 

The protective factors involved in the resilience process are both individual and environmental. 

At the individual level there are:

  • The ability to solve problems.
  • The independence.
  • Coping strategies.

Environmentally protective factors can occur within the family or the community. For example, within the family environment, protective factors are, among others: 

  • Relationships of trust and closeness.
  • Support from family members.
  • Adequate affective bonds with parents.

Challenges in the study of depression

ntive or treatment, as well as to work with patients to strengthen their psychological defenses against pathology. 

We hope that this article has been interesting for you and has resolved your doubts about whether depression is hereditary. As you have seen, and by way of synthesis, this emotional disorder depends on the interaction of the environment and genetics, therefore both factors influence its development. Today, progress is being made in the knowledge of genes or groups of genes that together facilitate a risk of presenting the disease and new treatment options.  

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