A recent study finding that parents exposed to viruses are less likely to become ill than are nonparents runs counter to the experience of many moms and dads with their little germ factories -- uh, darling children.

The study's leader, Sheldon Cohen, professor of psychology at Carnegie Mellon University, specializes in studying the ways psychological stress, social support networks and status influence immune systems.

Cohen and his team correctly surmised that "being a parent can be stressful." But the researchers also considered that being a parent could provide a sense of purpose and help establish supportive social networks.

They exposed 795 adults to a common cold virus. Parents were 52 percent less likely to develop a cold than nonparents.

They "were unable to identify an explanation for this association." They simply didn't measure any psychological or biological differences between the parents and nonparents.

But they insist there must be some psychological benefit of parenthood that let so many more shrug off the viral assault.

With all respect to the learned researchers, those of us who have manned and womaned the tissue boxes, vaporizers and mops with sick kids over the years know the reason: We're battle-hardened. We've got kids. Who has time be sick?