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It's the end of a long week. You're tired, lacking the energy to put on your coat and go to services. But you go anyway.

You greet old friends, rise for the prayers. Suddenly you're singing and your spirits are soaring. The aches have disappeared, along with the doldrums.

Is it prayer? Music? The presence of friendly faces or the promise of challah and chocolate chip cookies at the oneg?

Is it faith, the power of ancient words or the power of community?

Whatever it is, it makes you feel better, and now a study published in the International Journal of Psychiatry has confirmed what the devout have believed for years: Attending services is good for what ails you.

Older adults who attend regular religious services are twice as likely to have strong immune systems as those who don't, according to Dr. Harold Koenig, a Duke University psychiatrist and lead author of the report.

"Those who go to church or synagogue regularly are physically healthier, mentally healthier and they have healthier immune systems," the researcher told the Associated Press.

In his study, part of the largest national survey ever conducted on aging, Koenig determined that blood levels of interleukin-6, an immune system protein linked to age-related diseases, were lower in 1,718 test subjects over age 65 who attended religious services at least once a week.

Koenig and researcher Harvey Cohen, director of Duke's Center for the Study of Aging and Human Development, found that the benefits linked to religious attendance continued even in the presence of such factors as age, chronic illness or depression.

So what does it all mean? In addition to regular exercise, rest and chicken soup, adding services to your weekly routine may improve your health.

It would certainly improve the health of the Jewish community.

In any case, it couldn't hurt.