Depression is one of the most common mental illnesses, with millions of people suffering from major depressive disorder in the United States alone. In spite of its popularity, many people wonder if it is hereditary. Genetics is not the only factor, however. There are also non-genetic and epigenetic factors.
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Genetics
In this study, researchers analyzed data from several databases, including the Million Veterans Project, UK Biobank, and FinnGen (1.3 million customers of 23andMe). They discovered that certain genetic variations were related to depression.
These findings raise many questions, including whether depression drugs are effective. However, it should be noted that this study only looked at common variants, not rare variations. This means that researchers have to identify rare variants.
To identify rare variants, they must use large GWAS sample sizes, which are imputed to large sequenced reference samples. Such approaches are becoming increasingly feasible and offer sufficient resolution for the low frequency range. However, they do face challenges when it comes to identifying genes that are linked to it.
Non-genetic factors
While genetics is one of the most common factors influencing it, non-genetic factors are also important. Some studies suggest that polymorphisms of serotonin transporter genes may play a role in depression.
These polymorphisms are associated with an insufficient amount of serotonin in the brain. Some people with depression are also prone to high levels of activation of the hypothalamic-pituitary-adrenal (HPA) axis. While this activation may not be the only cause of it, it does increase the risk.
Despite these risks, researchers have not identified a single gene that causes it. Researchers believe that combinations of genes from both parents can contribute to a person’s risk of developing it. In addition, they are unsure which specific gene groups may be linked to the development of it.
Serotonin levels
You might have heard that people with low serotonin levels have a hereditary link to depression. While this is not entirely true, it can make a person more prone to the disorder. There are genetic variations in the serotonin transporter gene, which may explain why people with certain genes are more likely to develop the disorder.
Serotonin regulates a large number of interrelated biological functions, including mood and behavior. A recent study found that genetic variations in serotonin levels may be linked to the development of depression. Other studies have shown that certain therapeutic strategies to improve serotonin activity may help people with it.
Epigenetics
Recent studies on epigenetics and depression have focused on the role of the amygdala and hippocampus. Other regions of the corticostriatal-limbic circuit have been less well studied. Epigenetic changes to the amygdala have been associated with depression and anxiety.
Researchers have found that chronic social defeat stress increases the acetylation of H3K14 in this region, but the acetylation returns to baseline after a longer period of time. Injection of the HDAC inhibitor MS275 into the amygdala reverses social avoidance and it in mice.
Epigenetic changes have been reported in human studies and animal models of it, although more work is needed. Researchers have recently begun to investigate the role of these changes in the treatment of it and other mood disorders. A key area for future research understands the role of early life stress on gene expression.
Family history
A family history of it is one of the most reliable risk factors for the development of future mental illness. It has been associated with an increased risk for major depressive disorder, other nonpsychotic disorders, and unnatural deaths in biological offspring. These disorders often begin in childhood or adolescence.
Family history of mental illness has also been linked with stable differences in brain structure, including smaller subcortical volumes and reduced cortical thickness. In addition, family members with a history of it are more likely to exhibit altered resting-state functional connectivity.
In addition to genetics, another risk factor for it is environmental exposure. Mental illness is more likely to strike women than men. Hormonal changes in women can increase the risk for depression. Genetics of it are complicated and not straightforward as those of other diseases. However, a family history of it increases the risk of it by two to three times.
Treatment options
Although you can’t change your genes, you can make changes to your environment and lifestyle to improve your chances of avoiding depressive disorders. Studies show that depression can be hereditary and is responsible for 40-50% of it, but there are also other factors that can play a part. If you’re worried about heredity, talk to your doctor or therapist.
Also, gender may play a role in hereditary illnesses, as women are more likely to have depression than men. The brain’s serotonin levels are also linked to a person’s risk of developing it. Serotonin is a “feel good” chemical that helps nerve cells communicates with one another. When serotonin levels are too low, mood disorders and other problems can develop.
