As scientists continue to make progress in decoding the human genome, we’re constantly getting closer to understanding the cause of some of the most common and uncommon illnesses. We’ve been able to pinpoint the location of defective genes which cause rare, debilitation conditions like Huntington’s disease, cystic fibrosis, and even some types of muscular dystrophy. But, is there a link between genes and depression?
It’s still unclear whether more common conditions — things like diabetes, high blood pressure, and depression — have any single genes or groups of genes associated with their prevalence. As far as we know, there is no depression gene, and yet the link between genes and depression is becoming more and more apparent as research continues.
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According to Psychiatry.org, depression is a common and serious medical illness that negatively affects how you feel, the way you think, and how you act. Although they can vary, symptoms often include:
- Prolonged feelings of sadness
- Loss of interest in favorite activities
- Changes in appetite
- Difficulty sleeping
- Decreased energy
- Feelings of worthlessness or guilt
- Difficulty concentrating
- Thoughts of death or suicide
When symptoms last for at least 2 weeks at a time, someone is said to have clinical depression. Although with one in 15 adults experiencing depression in any given year, scientists are briskly working on finding out whether there is truly a link between genes and depression.
Recent Studies and Emerging Information
Now, the culmination of past research and new ways to study this link are beginning to emerge with promising implications.
Studies of twins have already found that if one twin has depression, it’s likely that the other will also develop the condition when compared to non-twin siblings. According to Dr. John H. Krystal,
“We know there is a heritable quality of both unipolar and bipolar depression… If you don’t have a family history of depression, then it tends to develop only in the context of stress.”
Otherwise, disorders such as schizophrenia and autism also show strong genetic signals and associations with depression, however, the samples to identify these genes in the context of these conditions is absolutely enormous. So how can science cut through the noise to understand the link between genes and depression?
23andMe’s Consumer Genetic Studies
Thanks to the consumer genetic analysis company 23andMe, a 2016 study was able to acquire the large sample size needed to start understanding some of the genetic links that may be responsible for depression. By studying 75,000 23andMe customers who self-reported a clinical diagnosis of depression in combination with 231,000 individuals with no reported history of depression, researchers were actually able to locate 15 regions in the human genome said to be associated with the condition.
The findings were then replicated in another sample of 45,000 cases of clinical depression, further confirming the validity of this insight. Additionally, 23andMe announced they are seeking to enroll 15,000 people with depression and 10,000 additional participants with bipolar disorder to continue mapping how genetics and one’s environment contribute to the prevalence of these mental illnesses.
Moreover, it’s becoming apparent that the link between genes and depression may not be as obvious as one single genetic marker as in other serious diseases. Researchers like Steven E. Hyman contend that science may eventually work toward identifying series of small genetic changes, which can be used to understand someone’s genetic predisposition to depression. Similar to how heart disease is a culmination of risks of high lipids, high blood pressure, smoking, etc., depression may be similarly understood in light of more research into specific areas of the human genome.
The environmental factors known to worsen depression such as stress, poor nutrition, and lack of exercise make studying the genetic links between this condition hard to sort out. Still, researchers are hopeful that even with these caveats, several more years of research will begin to stratify these genetic links until the next breakthrough in genetics.