Depression has an inherited component, but genetics is only one part of the cause. We discuss the intermix of genetic and environmental factors that cause depression.
Is depression genetic? The short answer is “yes.” However, it’s not quite so simple as yes or no. As with just about anything that involves the complex human body, there are many factors that affect the genetics of depression.
For one, there is no single “depression gene.” As of 2019, more than 80 genes that are related to depression have been identified as a result of intense research into this area, and there are probably many more yet to be uncovered.
All genes are contained in DNA. These genes decide many of an individual’s physical characteristics and even personality traits. However, people are shaped biologically by two factors: “nature” and “nurture.” “Nature” is the genetics and “nurture” is the combination of environmental influences that shape people — how they are brought up, their education, nutrition, life experiences and so on.
Some things are only determined by nature (genetics) — such as eye color — while some things are determined only by nurture — such as which high school a person goes to. Most characteristics result from a combination of the two, such as whether or not an individual will develop depression at some point in their lifetime.
People often have multiple copies of the same gene. The complex mix of how many depression-related genes an individual has, how many “bad” copies of these genes are present and how many “good” copies the individual possesses, all combine to form a genetic risk for depression.
Genetics alone do not determine whether or not an individual will one day become depressed. Rather, the genetics merely make up the individual’s predisposition — likelihood — of developing depression. So, in the end, the individual’s environment (life experiences, influences, and situation) comes heavily into play.
While clinical depression does tend to run in families, and there is certainly a genetic component. To really understand the heredity of depression we have to look closer at the whole picture.
Depression and Heredity
Because there are so many depression genes and a multitude of possible combinations of these genes, there is currently no way to determine a particular person’s genetic likelihood of developing depression, regardless of that person’s family history.
Based on extensive studies of large numbers of people with depression, it appears that the hereditary aspect of depression is about 42% for women and 29% for men. This highlights the fact that many of the depression genes are located in female sex-genes, and that women are at higher risk of inheriting depression.
For the general population, the lifetime risk of developing depression in the U.S. is 16.9%. Having a sibling with depression elevates that risk by about 1.5 times while having an identical twin with depression elevates the risk by about 2.8 times.
These numbers demonstrate that having a family history of depression is far from being a guarantee that an individual will develop depression. They do show, however, that the risk is higher for people with family members with depression than for the general population. As such, people with a family history of depression may be wise to take some precautions, including:
- Learn the signs of depression, so that they will be able to quickly identify these symptoms in themselves and family members
- Take measures to improve their resilience, hardiness, and vulnerability to stressors, such as learning better-coping skills or attending counseling in times of stress
- See their doctor early on if they feel they may be developing depression
The Depression Gene
Many of the genes involved in depression affect various brain functions, especially the production and metabolism of the brain chemicals (neurotransmitters) and various hormones that impact mood. Neurotransmitters are the chemicals that our brain cells use to form connections and pass information.
With so many “depression genes” having already been identified, and probably many more to come, we can see how complicated the issue is. While some diseases (such as cystic fibrosis) are caused by a single faulty gene, that is far from the case with depression, and there is no single “depression gene.”
About one-third of people with depression are treatment-resistant, which results in a worse course of illness and poorer outcomes. Recent research evidence suggests that it may be genetic factors that cause certain people’s depression to be resistant to treatment.
Some genes are related to especially severe depression and a high risk of occurrence. For example, a gene was identified on chromosome 3 (called 3p25-26) that is linked to severe recurrent depression.
The discovery of genes related to depression is encouraging development in our understanding of this common mental health disorder because it can help lead to new and highly effective therapies. For example, physicians will be able to target therapies at specific neurotransmitters based on the individual’s genetic profile, and gene therapy will become an option for correcting “bad” depression genes.
Environmental & Other Factors
Genetics only determines an individual’s predisposition or how likely they are to develop depression. The rest is determined by the individual’s environment.
The environmental causes of depression are those things that make up the individual’s experiences and exposures in life. The most significant of these include:
- Childhood trauma: neglect, physical abuse, sexual abuse or emotional abuse. The trauma can be a single event, multiple events or even prolonged trauma, such as years of sustained bullying at school, general maltreatment or poor parenting
- Life stresses: these are the triggers for depression. They include such things as financial stress, life transitions, grief and loss, and rumination
- Overall health: nutritional status (especially while the brain is developing up until age 25), as well as an individual’s resilience, hardiness and vulnerability to adverse conditions
- Illness: certain illnesses are strongly associated with depression, and some medications are also known to induce depression
In addition, the World Health Organization (WHO) has identified a number of social and economic factors that are associated with mental health disorders, including depression:
- Access to health care
- Social isolation
- Living environment (neighborhood)
- Level of income
- Level of education
- Nutritional status
Therefore, whether or not an individual will develop depression at some point in life depends on the interactions between that person’s genetic predisposition to depression and the presence or absence of these environmental factors.
Is Depression Curable?
Depression is treatable, usually easily so. Current medications are very effective for most people, and psychological therapy, such as cognitive-behavioral therapy (CBT), is also effective, especially for situational depression. About one-third of depressed people will have treatment-resistant depression and will require specialized care.
While depression is treatable, successful treatment is considered to be a remission rather than a cure, because depression sometimes comes back. By treating depression not only with medications but also with appropriate counseling, the risk of relapse is reduced. That is one of the reasons that comprehensive treatment works best.
People with undiagnosed or untreated depression are at high risk for the co-occurrence of depression and substance abuse. This is because they may use addictive substances to “self-medicate” their depressive symptoms. This begins a vicious cycle where depression worsens substance use and substance use worsens depression.
The Recovery Village offers comprehensive, specialized assessments and treatment programs for addiction and co-occurring mental health disorders. If you are concerned about addiction and depression in yourself or a loved one, contact The Recovery Village for a confidential discussion with an admissions coordinator.
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