Depression: It's Not Just In Your Mind, It's Also in Your Genes

Depression is an extremely common condition. In 2010, the US Centers for Disease Control (CDC) released a report finding that nearly 1 in 10 Americans suffered depression, and 1 in 30 suffered the more severe form of the illness, major depression. About 1 in 8 American women and 1 in 12 American men suffers at least one episode of major depression during life, and people in other countries are diagnosed with depression at about the same rate, with exceptions for some European countries such as Sweden and Hungary, where depression rates are unusually high.

Recent research has uncovered a genetic connection to depression, explaining how some people are more susceptible to depression. Knowing how the disease occurs suggests ways for preventing it, sparing tens of millions of people this debilitating, socially stigmatized condition.

Depression Is In DNA

A group of medical researchers at Stanford University took note of the finding that people who suffer major depressive disorders typically also have characteristic changes in their DNA. In people who deal with this relatively severe form of depression, the ends of the strands of DNA have shortened "buffer zones" known as telomeres. Formerly though of as junk DNA, telomeres exist to make sure the cell can line up the two strands of DNA to make a functioning double helix with the A, G, C, and T nucleotides in the right sequence.

If the strands of DNA don't line up, they aren't functional. As the telomeres get shorter and shorter, the cell is less and less able to reproduce itself without damaging its DNA. When the telomeres get too short, they cell cannot reproduce itself at all. If it dies, there is a tiny hole left in the tissue, and the inflammation required to get rid of the dead cell can damage healthy cells around it. People who have major depression tend to have lots of these DNA-damaged cells.

Stress Leads to Depression, Depression Leads to DNA Damage

What is it about depression that causes DNA damage? The Stanford research team decided to find out by recruiting 97 healthy girls aged 10 to 14, half of whom who had mothers who had had major depressive episodes, half whom did not. None of the girls had been diagnosed with depression, and the scientists expected that the girls' DNA would contain healthy, youthful, long telomeres, indicating no DNA damage yet.

However, when all of the girls were given a stress-inducing experimental task, the scientists found that levels of cortisol, a stress hormone, went up in the girls whose mothers had history of major depression. Cortisol levels did not go up in the girls whose mothers had not had bouts with major depression. Both groups of girls had normal stress hormone levels before doing the experimental task, which suggests that some of the girls made more stress hormones than others. Even though these girls did not show signs of stress or depression, their telomeres were already shorter than those of the other girls.

See Also: Understanding Depression: When Feeling Sad Is A Sign Of Mental Illness

The scientists tracked the girls to age 18. By the time the girls reached adulthood, about 60% of them who (1) had mothers who had had depression and (2) had higher cortisol production developed depression and (3) telomeres in DNA shortened before the onset of depression. Stress was changing DNA in ways that predict depression before it occurs.

Testing for Depression, and Doing Something About It

The Stanford University researchers used saliva (spit tests) to measure the telomeres of DNA. Shortened telomeres predicted stronger reactions to stress and development of depression as the girls matured. These finding suggest a very simple test for risk of depression, just collect a saliva sample (it's not even necessary to draw blood, and it's not necessary to take a battery of psychological tests) and within a few hours the doctor will know whether the patient is at risk for major depression.

Of course, an even easier way to know a patient is at risk for major depression is to look at family history. In this study, girls whose mothers had had major depressive episodes were at greater risk for depression. Depression isn't just transmitted from mother to daughter. People who have immediate family members (mother, father, brother, sister) who have major depression are about 3 times as likely to develop major depression as people who do not. When one twin has major depression, about 40-50% of the time the other twin eventually develops major depression. Environmental factors determine the timing and severity of the disease, but the propensity to the disease seems to be related to the genes.

If you know you or a family member is at high risk for depression, what can be done? Here are some possibilities:

• Exercise. Aerobic exercise, especially high-intensity aerobic exercise and dancing, reduce depression. Strength training has other benefits but has not been shown to reduce the severity of depression or to prevent relapses after a major depressive episode.
• Eat your veggies, but avoid sweets. Diet has an effect on depression in most people. Eating fewer vegetables is associated with fewer bouts with depression, while eating sugary sweets is associated with more, although there is some question whether eating sweets causes depression or eating sweets is an attempt to self-medicate depression.
• Avoid diet drinks, but drink coffee. A study of depression in older Americans found that drinking aspartame-sweetened soft drinks such as Diet Coke increased the frequency of depression, but drinking coffee reduced it. Adding artificial sweeteners, such as Splenda or Sweet n' Low, to coffee and tea was associated with more frequent depression, but not adding sugar or honey. Presumably the amounts of sugar or honey added to beverages is not so great as to cause its own problems. Small amounts of sugar, up to about 25 grams (less than an ounce) a day in total, seem to help some people overcome depression.
• "Mindfulness meditation" seems to help both depression and anxiety, although most clinical studies of the use of meditation have been conducted in Western countries. Most Western psychotherapists attempt to train their patients to be "in the moment" and "open to experiences" to relieve depression. Patients are encouraged to observe and describe their feelings and experiences, to act with awareness, but not to judge emotions or inner reactions as either bad or good.

See Also: Treating Depression Lowers Your Risk Of Heart Disease

Prescription medication may also help prevent relapses of depression, but no single medication seems to work for everyone, and it may take several months to get the right dosage of the right drugs to feel better. Do not use both St. John's wort and antidepressants; the cumulative effect can cause severe physical and emotional hyperactivity.