Whether your circle of friends includes individuals you've known since your elementary school days right up to the present, or it's made up of mostly people you know through your kids, chances are they are important to you. You rely on them for companionship, socializing, advice and support. Friends can be a sounding board and a source of calm when siblings get under your skin, and they pave the way to helping you put things into perspective. They are quite simply, a gift.

But friendships, much as they are treasured and nurtured, don't always last forever. Whether it's you who's deciding to let a relationship with a friend taper off or it's your friend who's sending clear messages that you're just not that close, experiencing the loss of a friendship can have negative health consequences.

"Your heart can be broken when a friendship ends," says Bonnie Eaker Weil, Ph.D., author of Make Up, Don't Break Up. "It definitely affects your health when you lose the love and support of a friend."

When you're friends with someone, you both get what Weil calls "a dopamine high" when you help each other just by listening and being there. When that friend is no longer emotionally available, "You've lost your support system and it affects the immune system," Weil says.

A fading friendship "can be devastating to your health," agrees Carole Lieberman, MD, a Beverly Hills psychiatrist. "It can bring on depression and self-blame which, in turn, have physical consequences."

Depression can cause a lack of interest in the outside world, lethargy, problems with appetite, and difficulties with sleeping. And even if depression doesn't result from the ending of a friendship, sadness and feelings of loss often do.  

"When something like a misunderstanding causes someone to cut off a friendship, or when a friendship fades simply because the people have too little time to nurture it this can cause true sadness," Lieberman says.

When a friendship fizzles, it has an insidious effect on your health that you may not even realize at first, says Toni Galardi, Ph.D., author of "The LifeQuake Phenomenon: How to Thrive Not to Survive in Terms of Personal and Global Upheaval." "When you internalize you feelings and don't discuss them, it affects the immune system in a negative way," Galardi says.

If you and a friend are experiencing a rough patch in your relationship, here are some ways to smooth the way.

Talk things out.  If things aren't going well but you don't want to lose the person as a friend, "Address the issue with the person in a kind and loving way," Galardi says.

Recognize that some friendships just won't stand the test of time. If a friendship is impacting you in a negative way, you may need to end it. "If someone is constantly in crisis and you always have to be the counselor and the problem solver, you may need to rethink things," Galardi says. Signs that a friendship just may not be worth it include feeling like someone has just sucked the energy out of you after you get together, or feeling emotionally spent every time you get off the phone with that person.

 ● Don't discount a friendship you've enjoyed in the past but which seems to be faltering. "Real friendships are rare and valuable commodities today," Lieberman says. Friendships take time to nurture, so making space in your busy life for a friend you want to keep is crucial.