In the eternal debate about the differences between men and women, there is at least one thing that all sides agree on: Women suffer much higher rates of depression than men do.

One of the leading researchers into this phenomenon, Susan Nolen-Hoeksema, a psychologist at the University of Michigan, says women are more prone to depression than men in many countries, many cultures and many ethnic groups. This has led some theorists to suggest a biological basis for women's depression, though little evidence to support this has been found.

In a study published in November's Journal of Personality and Social Psychology, 1,100 adults from 25 to 75 years of age were interviewed twice, with a year between interviews. The study, supported by the U.S. Public Health Service, was conducted by Nolen-Hoeksema and two other psychologists, Carla Grayson and Judith Larson. They found that women are more vulnerable to depression than men because they are more likely to experience chronic strain, to have a low sense of control over their problems and to brood over their problems instead of finding solutions and getting on with things. They also found that once women get into this cycle, it's very hard to escape from it.

Many women suffer stresses and strains because they have less status and less power in society and they have to do housework and child care in addition to their work in the paid labor force, Nolen-Hoeksema says. On top of this, many women said they felt their spouses don't respect them and don't appreciate the contributions they make to the family. They feel overworked and underappreciated. Then they start brooding over their problems.

"Rumination is the tendency to think a great deal about problems and how you feel about them," Nolen-Hoeksema says, "and not do anything about them. A ruminator thinks about how tired she is, how unmotivated she is, how upset she is and all the reasons for this -- her problems with her job, her marriage and kids -- and she doesn't take action to do anything about these situations. We've got a lot of research that says girls and women are more prone to engage in rumination than men are."

Many women feel their lives are out of their control, that nothing they can do will help. "Women have problems in all three of these areas: They have more chronic strain. They are more prone to ruminate. They have a lower sense of mastery. All three of these things seem to contribute to depression and to the fact that women are more depressed than men are."

The researchers also found a cycle. "The more chronic strain you have, the more prone you are to ruminate and feel out of control," Nolen-Hoeksema says. "In turn, the more you ruminate and feel out of control, the less you do to change your circumstances, and so you build up more chronic strain over time. The upshot . . . is, women get caught in these negative cycles that make it very hard to pull out."

This finding is important, Nolen-Hoeksema says, because it helps explain why women don't do something to change their circumstances when things go bad. "The psychology and the social circumstances feed on each other in ways that make it very difficult to pull yourself out," she says.

One of the first steps to breaking this cycle is to understand it, Nolen-Hoeksema says. "Basic education goes a long way to making people feel they're not crazy," she says. "It's not just them. There is a process they've fallen into that is tough to deal with. One of the things we suggest is talking to a trusted friend about one's situation. This can help, but it can help primarily if this friend helps you sort out your thoughts about your situation and decide what you can do to improve it. Just sitting and ruminating with friends doesn't help."

Other research that Nolen-Hoeksema has done shows that people, and women in particular, who tend to feel they're responsible for everybody else's welfare and happiness, who aren't able to say no, end up ruminating. "You feel as though you take on all of these things," she says. "You resent them. You think a great deal about how you're being exploited, but then you worry a great deal about whether others are happy, what you can do to improve the relationship with the person you are thinking about." Her research into suicidal behavior points to the idea that "ruminators are more prone to impulsive behaviors to try to cut off all of these thoughts."

Research also has shown greater rates of depression during holidays, although suicides go down during holidays. "The standard explanation is that people keep it together during the holidays," Nolen-Hoeksema says, "but the letdown after the holidays and the effects of really short days, which definitely affects mood, contributes to the increase in suicide in January and February.

"The thing about rumination is when you get into these cycles, you do a worse job of problem-solving than you are capable of. You dredge up negative memories of the past and negative thoughts about your situation. We recommend taking breaks and then going back and engaging in more problem-solving, often with a friend, so you can go back with a normal perspective."

What's particularly valuable about this research is that it makes the connection between the very real problems women face -- pay discrimination, sexual harassment, poverty, a sense of being powerless, family violence, the strain of managing work and family -- and how we cope with them. Men, who tend to get on with things, may have a healthier coping mechanism than women.

My mother had a saying that put this in a nutshell: "There's no sense stewing over it." It looks like she was right.