Antidepressants not only treat depression, but can also help prevent heart disease. The scientists who have made this discovery think that improved mood makes the difference, rather than direct action by the drugs.
People who suffer from severe depression are up to four times as likely to die from heart disease triggered by obstructed blood flow as people who are not depressed-even allowing for classical risk factors such as smoking and high cholesterol levels. In fact, depression is a greater risk factor than smoking.
In 1996, Dominique Musselman of Emory University in Atlanta, Georgia, and her colleagues tried to find out if depressed people are at risk because they have higher levels of sticky platelets in their blood. Following injuries, platelets stick together and clot to stop us bleeding to death. Too much clotting would cause heart problems.
The researchers took blood samples from both depressed and healthy people and examined their platelets for evidence of stickiness. They measured characteristic chemical changes that occur on the surfaces of platelets as they prepare to clot and become sticky. The numbers of sticky platelets in depressed people, they found, were 41 per cent higher than in healthy volunteers.
Now the team has shown that anti-depressant drugs can cut down the numbers of sticky platelets in the blood of depressed patients. They monitored 15 patients taking a drug from a class of antidepressants known as selective serotonin reuptake inhibitors, which includes Prozac. The number of sticky platelets fell in all the patients, and even dropped back to normal levels in some of them, Musselman told a meeting of the Society of Biological Psychiatry in Washington DC last week.
"Treatment diminishes the stickiness of the platelets," she concludes. But one big question still remained. Does the drug lower the platelet stickiness directly, or does a happier mental state do the trick?
To find out, Musselman is running a placebo trial. Early results suggest people who don't report any improvement in mood after taking antidepressants also don't have much reduction in platelet stickiness. In contrast, people whose mood improves even with a placebo do show less platelet stickiness. This result suggests that mood improvement is the key.
Author: Alison Motluk New Scientist issue 22 May 1999
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