The secrets to strong friendships at any age.

 Friendship is good for mental and physical health - research show that having close friends raises self-esteem, boosts immunity and improves sleep. A study from Flinders University in Australia even found that people with many close friends live longer than those with few friends.

Friendships begun in childhood are especially powerful, providing a connection to the experiences that have made us who we are.

Best-selling writer Jeffrey Zaslow spent two years getting to know a close-knit group of women, now in their 40s, who met as girls in Ames, Iowa. As the 11 women moved to different states, pursued careers, married and became mothers, they maintained a powerful bond that has endured to this day.

What is different about the Ames girls that has allowed their friendship to last so long?

They are not as unusual as you may think. I first learned about this group of women after writing a Wall Street Journal column about turning points in women's friendships. Hundreds of readers wrote to me in responsee, describing their own lifelong friendships. Jenny - one of the girls from Ames - was among them. I was surprised at how many people I heard from who had been able to keep their fiend-ships strong over the years.

What do long-term friendships give us that short-term ones don't?

Newer friends may know us in a limited context - as colleagues, as volunteers, or as someone's spouse or parent. Friends from childhood or college have a fuller picture of us. They see beyond the roles that we have assumed in life. They see the ways that we have changed.

Longtime friends can provide a greater depth of emotional support during difficult tines.

For example, when Marilyn's father developed Alzheimer's disease, her newer friends in Minnesota knew her farther only as someone with dementia. Her friends from Ames remembered him as the beloved pediatrician who often gave them wise, practical advice and served the community with dedication for many years. These memories were a great comfort to her.

How are men's friendships different from women's?

According to research, men continue building friendships until around age 30, after which the number of friends steadily declines. Men then tend to get their emotional needs met by their wives. In contrast, women tend to neglect their friendships most in their 20s and 30s, while they are raising young children, but return to them when they reach their 40s and beyond.

One dramatic difference between men's and women's friendships is that women build trust by talking about highly personal topics. Men's conversations with one another tend to be less personal - they bond by doing things together.

How can people go about reconnecting with old friends?

Technology can help. Look up your old friends on Facebook.com or through your alumni association's database.

There even are web sites, such as Classmates.com, designed to help you find old friends. Then sand an e-mail or a note - a few paragraphs catching the person up on your work and family or news from your old town or school.

You may have fewer interests in common with older friends than with newer friends. Focus on the commonalities - the history and memories that you share.

Keep expectations modest, and read the social signals. If your five paragraph missive about your life gets a one-sentence reply, don't take it personally. Accept that the timing or the match may not be right, and reach out to other old friends. Can friendships formed in adulthood ever be as strong as friendships begun earlier in life?