Does grandma get to see your baby regularly? Grandmothers who take care of their grandchildren once a week, a small study showed, may be at lower risk of developing Alzheimer’s.

Why? Consider a story in Atul Gawande’s excellent book Being Mortal. He tells of seniors shuffling the halls in a nursing home, looking lifeless–until an idealistic director breaks the rules and brings in an unmanageable number of birds for the residents to take care of. Suddenly, the seniors have social interaction and purpose. The difference in their mental health is both visible and striking.

I know, kids aren’t birds. (Actually, mine might be, with all the flapping and flying she does around the house.) But many, many studies show the connection between mental health and social interaction or isolation.

In the Alzheimer’s study, women between the ages of 57 and 68 were given various tests of cognition. Those who scored highest were the ones watching their grandbabies once a week.

Don’t cancel that childcare contract, though. More babysitting isn’t better. Grandmothers who spent five days a week or more caring for little ones scored lowest on the cognitive tests. Mood was thought to be a factor there.

(And if the grandchild moves in, even when it’s best for the child, that’s even more challenging to grandparents’ mental health. Grandpa will spend more time at bars.)

That reminds me of an interesting bit in one of Jared Diamond’s books showing that in most societies, as it becomes economically viable, older people choose to live independently rather than with their children.

But a strong relationship continues to benefit the brain as the grandchild becomes an adult. Depression is less likely if grandparents have a strong bond with an adult grandchild, a separate study found. Researchers from the Institute on Aging at Boston College looked at data collected on 700 grandparents and grandchildren across 19 years. They found that the closer the relationship between the two, the less likely either was to develop depression.

What defines a strong bond?

• The child feels emotionally close to the grandparent.
• The child has regular contact with the grandparent.
• The child sees the grandparent as a source of social support.

Grandparents need to feel useful, too. The study found that if the grandparent received “tangible support”–like rides to a doctor’s appointment, help with chores, money, or advice–but was unable to give any tangible support to the adult grandchild, the grandparent was more likely to experience depression. Grandparents who both gave and received tangible support were least afflicted by depression.

“The greater emotional support grandparents and adult grandchildren received from one another, the better their psychological health,” lead researcher Sara Moorman said. At the midpoint of the study, the average age of the grandparents was 77; the average age of the grandchildren was 31.

Back to babies. They get a lot out of being around grandparents, too.

A richer sense of self. A link to family history and heritage. Another model for relationships. A feeling of safety. In some cases, grandparents can protect young children from depression as well. If mom is depressed, she’s less responsive to baby’s cues, less engaged, and less positive toward her child–but a grandparent’s strong bond helps minimize those effects on the child. Baby gets another person to talk to.

Bonus: Get the 3 best ways to boost baby’s language skills

Now what if you’re not feeling so sure about how your parents raised you? Take heart. In one survey of grandparents, 63% “say they can do a better job caring for grandchildren than they did with their own.” Or maybe you’re limiting contact because your parents don’t do things exactly the way you would like. Think hard about truly what crosses the line into harmful. If you’re leaning on grandparents for daily child care, have an honest conversation about how it’s going.

Help create that strong bond between grandchild and grandparent–apparently by not spending too much time together–and everybody wins.

Today is a good day to connect with the grandparents in your life, by the way. It’s Grandparents Day.

What else gives the aging brain a boost? Check out Brain Rules for Aging Well by John Medina, a developmental molecular biologist with a knack for friendly writing. I edited the book, so I read it quite closely. And, even though I’m not the target audience (AARP should not have sent me a membership invitation that one time!), I’m glad to know what’s in this book.

Written by

Tracy Cutchlow

Tracy is the author of the international bestseller Zero to Five: 70 Essential Parenting Tips Based on Science, a public speaker, and a creator of places to speak and be heard. Sign up for her newsletter here.