Slideshow: Sneaky Depression Triggers as You Age

Feel like middle age is closing in on you? You're not alone. A 2008 study of data from 2 million people found that midlife depression spans the globe. In the U.S., it peaks at around age 40 for women and 50 for men, and usually starts to lift in the 50s. Why? People may learn to adapt to their strengths and weaknesses and value life more, the researchers say.

Squeezed between the demands of children, aging parents, marriage, and your job? Feeling sad, worthless, and guilty? Women tend to shoulder more of the "sandwich generation" burdens -- and up to half become depressed as a result.

Solution: Make sure you're caring for yourself, too. Exercise, get enough rest, eat healthy, see friends, and get help -- for caregiving demands and depression -- if you need it.

If you're feeling lethargic or depressed, too little vitamin B12 may be to blame. If you're older, you're more at risk for the B12 blues because you may not have enough stomach acid to release B12 from food.

Solution: Ask your doctor to measure levels of B12 in your blood. If it's low, talk to your doctor about diet, oral supplements, or an injection to see what might be right for you.  

As men age, their bodies produce less of the important sex hormone testosterone. Low testosterone levels can cause depression, as well as erectile dysfunction (ED) -- trouble getting or keeping an erection -- and a decreased interest in sex. 

Solutions: Ask your doctor to test the levels of testosterone in your blood. If it is low, ask your doctor about replacement therapy and other treatment options. 

Depression can be one symptom of an underactive or occasionally overactive thyroid. And if you are older, it may be the only symptom. Or it may appear with a subtle symptom. In the case of overactive thyroid, it could be accompanied by heart flutters, tremors, or fatigue. An underactive thyroid can cause constipation or fatigue. That's why this very treatable problem is often mistaken for bowel or nervous system disorders in older people.

Solution: See your doctor, especially if a close relative has thyroid disease.

Living with a condition that causes chronic pain, such as rheumatoid arthritis or osteoarthritis, increases the chance of having depression. In fact, people with chronic pain are three times as likely to have depression or an anxiety disorder. And depression can make pain worse.

Solution: Exercise, meditate, or listen to music. An hour of classical music a day has been shown to ease arthritis pain and depression. If the depression or pain doesn't lift, talk to your doctor.

Hormone fluctuations, hot flashes, and life changes related to perimenopause and menopause can make your mood plummet. If you have trouble sleeping, a history of depression, or PMS, mood swings or depression may worsen during this transitional period.

Solutions: For mild depression, try self-calming skills such as yoga or deep breathing. Do things that make you feel better, such as exercise or going out with friends, or find a creative outlet. For more serious, long-lasting symptoms of depression, prescription medication or talk therapy can help.

If your child has left home, an "empty nest" can make you feel empty. Going through menopause or retirement at the same time may make it harder.

Solutions: Try to see it as an opportunity. Reconnect with your spouse, other family members, and friends. Pursue hobbies and interests you didn't have time for before. Give yourself time to adjust. If your mood doesn't lift in a few months, talk to your doctor.

Do you feel too listless to check your blood sugar regularly? Are unpredictable blood sugar levels making you feel out of control? Depression is a common and dangerous complication of many chronic conditions, including diabetes. Depression also may keep you from taking good care of your diabetes.

Solution: Talk to your doctor if you've been depressed for more than two weeks. Talk therapy, medication, and better diabetes control can help you manage both conditions. Depression is serious and if left untreated can be life threatening.

About 1 in 4 older people who drink heavily has major depression. Some older people start drinking more because of stressful events, such as retirement or a spouse's death. Yet alcohol problems are often mistaken for other age-related issues.

Solutions: A combination of medications can treat both alcohol dependence and depression. Individual or group therapy can also help deal with issues that may trigger drinking.

Insomnia and other sleep disruptions, which are common as we age, are closely related to depression. Insomnia can be a sign that you are depressed, and if you have insomnia but aren’t depressed, you’re at higher risk of developing mood changes. Obstructive sleep apnea and restless legs syndrome also have been linked to depression.

Solutions: Talk to your doctor about possible reasons for your sleep problems and get treatment for them. Learn good sleep hygiene habits, such as regular bedtime hours. Exercise early regularly and avoid caffeine, alcohol, or nicotine, which interfere with sleep. Prescription medication may also help.

If you were forced into retirement -- because of poor health or other reasons -- you might very well be depressed. Factors such as financial insecurity or lack of social support can also make retirement a downer.

Solutions: Busy retirees tend to be happier retirees. Learn new skills, take classes, get exercise. Be flexible: For example, if your health makes activities like travel difficult, take in museums and foreign films.

It's common to feel depressed after a diagnosis of heart disease or having a heart attack or cardiac surgery. But many people with heart disease go on to experience severe, long-term depression. And that can worsen heart health.

Solutions: A healthy diet and sleep, mild exercise, relaxation techniques, and joining a support group can help you get through the blues. If depression lasts, antidepressants or talk therapy can help.

Could the drugs you take for high blood pressure or other health problems also be bringing you down? Some blood pressure medicines -- as well as certain antibiotics, antiarrhythmics, acne products, and steroids, among other drugs -- may be associated with depression or other mood changes. 

Solutions: Be sure to ask your doctor if any new medications you may be taking could be linked with changes in mood. If it is, you may be able to switch to another drug.

Social support can help prevent or ease depression. But some kinds of social support may be better than others. A study of people in a retirement community found that those who stayed connected with friends living elsewhere had less depression. Support from within the community didn't affect mood.

Solution: Maintain ties with close friends and family members. Explore Internet technology that can give you virtual face-time with distant friends.

Any chronic or serious condition -- such as Parkinson's disease or a stroke -- can lead to depression. A stroke can also affect the areas of the brain that control mood.

Solution: Be realistic but positive. Learn how to cope with physical effects of your illness. Don't let them get in the way of taking care of yourself and having fun. If you have symptoms of depression, don't wait -- get help right away.

Feeling foggy and forgetful? It could be depression or dementia, a condition marked by memory loss. The signs and symptoms can be similar. Or it could be both -- depression is more common in older people who have dementia, especially Alzheimer's.

Solutions: If you don't know what's causing your symptoms, see your doctor so you can get the right treatment, if necessary.

It's normal to grieve after losing a spouse or other loved one. But grief can grow into depression. Memory problems, confusion, and social withdrawal can be symptoms of depression in older people. Both grief and depression raise the risk for heart-related deaths.

Solutions: Let yourself grieve. Express your feelings to friends, in a support group, or to a grief counselor. For depression, medication and talk therapy can help.

To keep your mood up, it helps to have good emotional and social support. But who says social support needs to be human? Studies show that pets can help people have less depression and loneliness and more self-esteem and happiness. Pets are friends with other benefits, too. Walking a dog, for example, is good exercise and a great way to meet people.

A good laugh can relax muscles, reduce stress, and relieve pain. And research suggests that a good sense of humor can take the bite out of depression. For humor on demand, create a laugh library of funny books, cartoons, and DVDs. Or try laughter yoga, which uses playful activities and breathing exercises to provoke giggles.

Helping others can help you forget your own problems. Volunteering feels good at any age, but it may hold special benefits for older people. If retirement has you adrift, for example, it can give your life a new sense of purpose and satisfaction. Recent research suggests that it may even prevent frailty in older people. Find a cause that has special importance to you and get involved.