Disorders and Treatment
- Mental Illness
- Bipolar Disorder
- Mood Disorders
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The development of depression is influenced by genes, but is likely not caused by a specific defective gene. A combination of genetic factors seems to predispose some individuals to the disorder.
So, we do not inherit depression directly from either parent. It is the unique mix of genes we receive from both parents that may make us more susceptible to depression.
Scientists know genes play a role in depression by studying patterns of illness in families; they have determined that 40 to 50 percent of the cause of depression is related to genetic inheritance. The percentage could be higher in cases of severe depression.
This can mean that in most depression cases, about half of the cause is gene related, and half is owed to psychological or physical factors. It may also mean that some depression is nearly 100 percent genetic, while other cases may have nothing to do with genes at all.
What further increases the likelihood of developing a depressive mood disorder is having a parent or sibling with symptoms of major depression. This at least doubles a person’s risk of depression onset.
The risk of developing depression increases even more when the parent or sibling suffers from recurring depression, especially if it started in childhood, adolescence, or their early twenties. Although this type of depression is not common, its family presence raises the rate of depression in children and siblings significantly.
Individuals who have relatives with bipolar disorder have a higher tendency of developing major depression or bipolar symptoms. However, most people diagnosed with major depression do not have close family ties to people with bipolar disorder.
Another depression risk factor likely influenced by our genes is negative affectivity, or the tendency to have unpleasant emotional reactions, including anxiety, in response to stress. Yet, many who develop depressive symptoms do not have negative affectivity before depression onset.
Although genetics are involved in depression, many other factors raise the risk of depression—including some we may not be aware of yet. Severe life stress (e.g., job loss, divorce), abuse or neglect during childhood, and losing a parent in childhood are associated with increased depression risk. Diet, environmental toxins, or other illnesses are factors as well.
Source: Stanford School of Medicine
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