August 2003

Research Capsules
by Harrison Wein, Ph.D.

Feeling Pain in the Brain
Some people seem to be more sensitive to pain than others. Do these people really feel more pain, or are they more vocal about their discomfort? For health providers, assessing how much pain a patient feels can be a real challenge when doing a diagnosis or trying to determine a course of pain medication. In a new study funded by NIH's National Institute of Neurological Disorders and Stroke (NINDS), scientists used brain imaging to show that people feel pain to different degrees, and that their descriptions of the pain they feel accurately reflects their levels of brain activity.

Seventeen people were recruited for the study. They were subjected to hot probes and asked to assess on a visual scale how intense their pain was. Researchers looked at the activity in their brains during painful stimulation using a technology called functional magnetic resonance imaging.

The scientists found that individual experiences of pain differed substantially. The most sensitive person in the study ranked the pain at almost nine on a scale of ten, while the least sensitive person ranked the same heat as causing pain of only a bit over one. Three regions of the brain — the anterior cingulate cortex, the primary somatosensory cortex, and the ipsilateral prefrontal cortex — were significantly more active in the sensitive people when they were exposed to pain. These three regions are all involved somehow in a person's conscious perception of pain. Interestingly, some brain regions that are involved in the transmission and processing of pain signals from the body weren't associated with differences in pain sensitivity.

Whatever the reasons some people feel pain more than others, their brains show that the phenomenon is real. This small study does not prove the case for everyone, but the researchers say that, in general, their findings validate people's own reports of the amount of pain they are feeling. The patient's own report, they write, "will likely remain the single most reliable index of the magnitude of pain."

— a report from The NIH Word on Health, August 2003

Proceedings of the National Academy of Sciences 100,14:8538-8542

For more information on pain, see Pain — Hope Through Research, a publication from NIH's National Institute of Neurological Disorders and Stroke, at http://www.ninds.nih.gov/health_and_medical/pubs/pain.htm or contact the Institute's Brain Resources and Information Network (BRAIN) at:

BRAIN
P.O. Box 5801
Bethesda, MD 20824
1-800-352-9424
www.ninds.nih.gov

Gene Linked to Depression
Researchers have found a gene that influences whether people become depressed when faced with major life stresses such as relationship problems, financial difficulties and illness. The gene by itself does not cause depression, but it does affect how likely people are to get depressed when faced with major life stresses.

Researchers funded in part by NIH's National Institute of Mental Health (NIMH) were interested in a gene called 5-HTT because it codes for a protein called a serotonin transporter, which recycles serotonin back into brain cells after the chemical has been released into the synapse, the gulf between brain cells. Serotonin is an important chemical messenger in the brain. The most widely-prescribed class of antidepressants target the serotonin system.

Everybody has two copies of 5-HTT. There are two versions of the gene, a short and a long version. Previous brain imaging studies, along with animal research, led the researchers to hypothesize that the short version may predispose people to depression. They followed 847 Caucasian New Zealanders, tracking their stressful life events — employment, financial, housing, health and relationship woes — from the ages of 21 to 26.

The researchers found that those who carried at least one short version of 5-HTT had more symptoms of depression, more diagnoses of depression, and more thoughts or attempts at suicide after stressful life events than those with two copies of the long version of the gene. Those with the short version of the gene were also at higher risk for depression if they had been abused as children. Significantly, among those who hadn't experienced major life stresses during the study, the gene played no detectable role in their risk of depression or suicide.

Depression, the researchers conclude, develops through a mix of genes and life events. Genes other than 5-HTT are doubtless involved in depression, and events in a person's life still play a primary role. Nevertheless, studies like this one may one day help scientists identify people who are more at risk for depression, and might eventually help doctors figure out which medications will help which patients.

— a report from The NIH Word on Health, August 2003

Science 301:386-389

For more information about depression, visit http://www.nimh.nih.gov/publicat/depressionmenu.cfm or contact:

National Institute of Mental Health (NIMH)
Office of Communications
6001 Executive Boulevard, Room 8184, MSC 9663
Bethesda, MD 20892-9663
Phone: 301-443-4513 or 1-866-615-NIMH (6464), toll-free
TTY: 301-443-8431; FAX: 301-443-4279
FAX 4U: 301-443-5158
E-mail: nimhinfo@nih.gov
Web site: http://www.nimh.nih.gov

Update — Lazy Eye Treatments
In the June 2002, issue of The NIH Word on Health (http://www.nih.gov/news/WordonHealth/jun2002/capsules.htm#lazyeye), we reported that eye drops could be used to treat amblyopia, or "lazy eye," the most common cause of visual impairment in childhood. Patching the unaffected eye has been the standard treatment for amblyopia, but many kids don't like the teasing or the skin irritation that comes with wearing an eye patch.

Now the same research team has found another effective treatment: reduced daily eye patching. After four months of treatment, children with moderate amblyopia who wore a patch daily for two hours over their unaffected eye showed the same improvement in vision as those who wore a patch for six hours. This finding should lead to better compliance with treatment and improved quality of life for children with amblyopia.

— a report from The NIH Word on Health, August 2003

Archives of Ophthalmology 121:603-611

For more information on amblyopia from NIH's National Eye Institute, visit http://www.nei.nih.gov/health/amblyopia/index.htm or contact:

National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
301-496-5248