Guilt still stings Carrie Nelson, usually in the mornings when the weight of a full day is on her mind.

Lying awake in her bed, she doesn't cry for past deceptions or for hurting her family or boyfriend.

Instead, she cries from guilt turned inward: constant thoughts that she's a liar, that if people really knew her, they would loathe her even more than she does herself.

For 21 years, clinical depression has been a part of Nelson's life, although she didn't always know it.

Undiagnosed until she was a high-school senior, depression erased all memory of her childhood. She said her mind "blocked it out in an attempt at self-preservation." Just as victims of abuse often repress memories, Nelson blocked out her self-abuse.

A teacher noticed Nelson's mood swings and, fearing for her health, contacted a counselor. Nelson said it saved her life.

The diagnosis of depression made sense to Nelson, but still shocked her. When depressed, she said, "you don't realize when you're slipping."

Four years later, Nelson, now a University conservation biology student, has dissolved most of the ties to her past. These days, she talks of working at an international animal preserve or doing Peace Corps work in Africa after graduation.

Yet she lives with the knowledge that her depression can never be cured. Her childhood demons still have the power to wipe out whole days of her life.

A common condition

University senior psychologist Rodney Loper said depression pervades all social and economic classes, earning it the nickname, "the common cold of mental health." In fact, one in 10 Americans are diagnosed with depression at some point in their lives.

The causes for depression are as numerous as the number of people affected.

"Depression," Loper said, "is the conversion of many pathways -- genetics, trauma, cognitive patterns and personal setbacks."

The interaction between the mind and body plays a significant role as well, he added.

But the consequences of untreated depression are largely the same: devastated self-esteems, health problems, chronic underperformance, distressed relationships, family pains or suicide.

Because of increased awareness, society is more accepting of depression now than in the past, Loper said.

But some cases, like Nelson's, drift by undetected for years because the stigma of being labeled "mental" or "weak" still remains.

Doctors discovered Nelson had low levels of seratonin, a mood-regulating chemical. She literally could not be happy.

A psychiatrist prescribed Prozac and, for the first time, the darkness in her mind lifted. Her mood improved and she even let herself believe compliments.

But hearing stories like this makes others misunderstand anti-depressants, Nelson said. Drugs don't make her high or alter her personality. Instead, Prozac makes it possible for her to feel happiness.

"I still suffer from down days just like any 'normal' person. That's the point. It makes me capable of feeling like a 'normal' person."

Because Nelson's depression was linked to her brain chemistry, doctors told her a relapse was likely and recommended she take Prozac regularly.

But Nelson chooses not to.

"You lose what little control you have (with drugs)," she explained.

Instead, she struggles with each new day. And sometimes the self-hatred wins.

University senior psychologist Glenn Hirsch said many people who are depressed have an aversion to antidepressant drugs and simply want to get by. To them, the high cost and stigma of a dependence on pills is not worth it.

But anti-depressants, Hirsch emphasized, simply restore the person's brain to its normal capacity, giving them "the mental energy to deal with their issues."