In 2003, mental health researchers announced that a genetic variation that affected the body's serotonin levels increased a person's risk for major depression if they endured several emotional events. Yet efforts to repeat and confirm that study's findings have been inconsistent, according to the National Institute of Mental Health.
Now, scientists reporting in The Journal of the American Medical Association say that genetic variation of the serotonin transporter gene, or 5-HTTLPR, may have no effect on depression risk.
The research team went back over data from 14 studies from 2003 through 2009 and analyzed the data collectively. Among the 14,250 patients in the studies, 1,769 had depression; 12,481 did not.
The analysis showed a strong association between depression and stressful life events across all the studies, confirming earlier research. However, the team could not find a link between the serotonin transporter gene and major depression. They also found no association between the gene and stressful life events on depression risk.
The scientists say their findings show why it is so important to confirm results that reveal any type of genetic association for a disease.
"A more serious concern ... is that the findings of this [earlier 2003 study] and other nonreplicated genetic associations are now being translated to a range of clinical, legal, research, and social settings such as forensics, diagnostic testing, study participants, and the general public," writes Neil Risch, PhD, of the University of California at San Francisco, and colleagues. "It is critical that health practitioners and scientists in other disciplines recognize the importance of replication of such findings before they can serve as valid indicators of disease risk."
If you think you might have depression, seek medical help. There are a number of different treatment options available to make you feel better. Depression is different for everyone. In general, symptoms can include:
- Persistent feelings of sadness, anxiousness, restlessness, and/or irritability
- Feeling hopeless
- Feelings of guilt, worthlessness, and helplessness
- Loss of interest or pleasure in hobbies and activities that were once enjoyed, including sex
- Fatigue, feeling "slowed down," or decreased energy
- Difficulty concentrating, remembering, and making decisions
- Sleeping troubles, including insomnia, waking up too early or sleeping too much
- Changes in appetite, which can lead to weight loss or weight gain
- Thoughts of death or suicide; suicide attempts (Seek help right away if this happens.)
- Physical symptoms that do not go away or get better with treatment, such as headaches, stomach problems, and chronic pain