Lately, when I talk about life's ups and downs with friends, I'm surprised to find how many are on anti-depressants. They swear by them. Indeed, the TV ads for these medications make them seem like a miracle drug, which for many they are.

But I wonder, are doctors prescribing and people taking these mood-lifting pills too readily? Isn't it OK to have a bad day anymore? I'm not down most days. But some days I am. Like when I'm behind in my work, I feel stressed. When I hear news of wars and kidnappings, I feel sad. When my kids are fighting instead of doing homework, I feel irritable. When money gets tight, or one of my parents gets sick, I feel anxious. When it's that time of the month, I feel all of the above. Is that a problem?

What is a normal mood cycle, anyway? What triggers bad moods and, most important, how can we manage moods -- short of medication -- so they don't manage us?

Though our genes mostly dictate whether we're generally sunny or sullen, external factors also play a huge role in whether we feel more blue than pink. Stress, travel, poor sleep, medications, light, hormones, pain, illness, caffeine and alcohol are all common mood disrupters. Any one of those can cause chemical messengers, or neurotransmitters, to be released in the brain, which can affect people differently depending on their genes, says psychiatrist John F. Greden, M.D., chairman of the department of psychiatry and executive director of the Depression Center at the University of Michigan in Ann Arbor.

Thus, depending on your brain chemistry, you could buoyantly shoulder a load of stress, or crumble at the smallest mishap.

Individual brain chemistry also makes certain people more susceptible to bouts of depression. In certain cases, the best relief does indeed come from antidepressants, most often the much-advertised SSRIs (selective seratonin reuptake inhibitors) sold under names like Paxil, Prozac and Zoloft.

"For some people it simply rights the ship," says Greden. "For others it may be life saving."

However, they're not for everyone. According to a study reported in the New England Journal of Medicine in 2000, SSRIs didn't help one-third of those people suffering mild to moderate depression, and weren't effective for half of those suffering chronic depression.

Furthermore, the side effects can include loss of sex drive, weight gain, insomnia and headaches. So before you fill a prescription, you might first consider other ways to get a handle on moodiness, especially if it's mild.

Reaching menarche, having a baby, the changes of middle age, menopause -- all these come with hormonal changes that can play havoc with disposition. Most women who feel their mood plummet for no obvious reason know to look at the calendar. Shifting hormones cause most women to experience some moodiness around their menstrual cycle. Usually women experience the physical symptoms of PMS first: malaise, headache, fatigue and breast tenderness. The emotional fallout comes a day or two later, says Jean Endicott, Ph.D., a professor of clinical psychology at Columbia University Medical School in New York City.

"In terms of a woman's monthly cycle, considering the first day of the woman's period Day 1, the best days of the month are Days 6 through 10," she says. "That's when most women can count on feeling their best."

Take advantage of those days, and plan for the worst ones, usually days 21 through 28. While most women can tolerate their PMS symptoms, 3 percent of women have what doctors call PMDD (Premenstrual Dysphoric Disorder), which is like PMS squared.

"These women experience severe mood and behavior swings before their period. They have great difficulty functioning at work and getting along with their family," says Endicott, a specialist in treating the disorder. "They come to dread those days." SSRIs often work well in the treatment of PMDD, she says.

Moods can get a little worse during the peri-menopausal years, which on average hits American women between the ages of 47 and 51. But here's the good news: After menopause, women get a "post-menopausal zest," says Santoro. On the whole, post-menopausal women have better mental health than men of all ages and younger women. "It's the opposite of what most people think."

"Men suffer from low mood, too," she says. "So you need to consider other factors like medication, age, underlying emotional problems and stresses. Moods are a mix of biology and every day life."

Greden agrees. "People don't do enough to link mood to their environment. People need to look at their lives and ask, 'How do the things I do affect and change the way I feel?' To really learn to manage your moods, he says, you need to be your own scientists.

Start by looking at your family, because you'll have some of those genetic tendencies. Ask close blood relatives what makes them feel up or down. Then document what sets off a bad mood in you.

Endicott tells patients with mood disorders to chart their moods in a journal. List the two or three most troubling symptoms: Low energy, irritability, tension, teariness, whatever. Then rank on a scale of 1 to 5 how each was that day. Note what day of your cycle it is, how much alcohol or coffee you consumed, whether you exercised, how you slept, and any medication you took.

After a couple months, you'll start to see a pattern. "For many the awareness is all they need," she says. "Once you can pin down when your low spells are coming and why, you feel more in control, and the moods don't take you by storm." During times you know will be difficult, get more exercise, decrease your caffeine consumption, get more rest, and don't schedule that big presentation for work, or your daughter's slumber party.