At its worst, it can consume your life.
"When you wake up, it's beautiful and sunny out and you have 33 zillion things to do. But instead you think, 'How am I going to get through this day? What do I hang onto?' " said Marie, a grad student.
For others, it can strike on a milder note.
"You're wishing you had someone to share an experience with, but there's a kind of paralysis," said Maxine, a 47-year-old writer. "That's when it takes discipline to pick up the phone and call someone."
Either way, it hurts.
"I went for a really long walk--about 30 miles--one Saturday," said Dennis, a 42-year-old Washington consultant. "I passed a lot of couples and started thinking, 'Gee, it would be fun to do this with someone else.'
"There's a feeling of emptiness, like there's a second half of you that's missing."
Links to Health
Researchers and mental health professionals are recognizing that loneliness is more widespread and important than once thought. New studies are providing a link with physical health, while estimates of the lonely reach as high as 50% of the population.
"It's symptomatic of a screwed-up society that doesn't provide opportunities for people to interact, or have places to go where they're comfortable," said Stephen Goldston, a psychologist with the Neuropsychiatric Institute at UCLA. "There's nothing that exists in communities like the student union at college, where you can meet people you're interested in without pressure."
Loneliness, he said, is more than not having a date on Saturday night: "It's a key factor on people's physical and mental health."
Marie, in her mid-20s, is a model student--a self-described overachiever who loves sports, music, socializing. "If you have all this, how do you tell someone that you're lonely?" she asked. "You go out of your way to hide this part of yourself. You don't deal with it."
After days so bad she wondered how she would live through them, Marie decided to seek therapy. "It's painful, and a lot of times you don't really know why," she said. "It's not that there aren't lots of people around you, or that you're not outgoing and social, but inside you feel different. To recognize that is to feel lonely."
It's not the easiest topic to bring up. "People are ashamed of loneliness," said Jeffrey Young, an assistant professor of clinical psychology at Columbia University. "Even books addressed to lonely people don't use the word in the title."
Loneliness is also tied up with machismo: Men aren't supposed to need anyone. Anne Peplau, a professor of psychology at UCLA, notes that it seems to be easier for women to admit to loneliness.
"If a survey uses the word loneliness, more women than men say they are," she said. "But if the question is, 'I wish I had more friends' or 'My relationships are too superficial,' men score equally high."
While the elderly have been portrayed as the loneliest group, surveys show the late teen-age years--17 to 19--as the worst.
"The teen-age years are times of social upheaval, when you leave your family and go out in the world. As you get older, there are fewer major transitions, and you also tend to develop more social skills," said Peplau.
Meanwhile, interaction studies at the University of Tulsa suggest that while lonely people are clearly less verbally skillful and socially adroit, they are nevertheless not overwhelmingly rejected by strangers. Instead, it's the lonely who do the snubbing.
"They expect their partners to reject them, but by and large they do not," said Warren Jones, a Tulsa professor of psychology. "It's almost as if lonely people fear rejection so much that, before someone could possibly reject them, they reject the other person. If you think no one loves you, it's easy to decide no one's love is worth anything."
For most people, the "garden variety" of loneliness is transient, gone as soon as they make friends at the water cooler or the grocery store. However, there's a minority for whom it is a continual companion.
"The cliches are good advice for most, but there's a subgroup for whom they don't apply," said Peplau. "For them, loneliness is not a temporary state but a fact of life."
In the typical profile, these people had a parent who was unloving or absent. The person then ends up constantly fearing he will be rejected or he avoids relationships altogether.
In family situations in which a parent consistently favors another sibling, a person can develop a feeling of mistrust, rejection or inferiority, said Young. Later in life, the individual will tend to anticipate that his partner will find someone better.
Testing Your Partner
"The usual pattern is to then put your partner in a testing situation, constantly saying 'Do you really love me? Why did you say that? Pay attention to me rather than him.' " The result: The partner is driven away, and the lonely person is reassured that he's unlovable.