Music can improve your mood, but it depends on what you're listening to. In a recent study, volunteers' moods improved when they listened to Mozart but stayed the same when they heard other instrumental music, and their moods were made worse by music from the Holocaust movie “Schindler’s List.”

A recent study found that people who consume a lot of olive oil are less likely to be depressed. Salmon and walnuts are good sources of omega-3 fatty acids, and some studies have suggested that these essential fatty acids could have mood-boosting properties. Some research also indicates that eating high-calorie comfort foods, which we typically reach for during times of stress or anxiety, may be a type of “natural reward” that reduces stress responses.

A University of British Columbia study found that even brief interactions with strangers tended to improve people's moods. Researchers theorize that people tend to try to impress strangers and act cheerful around them, which has the collateral effect of putting them in a better mood.

Australian researchers studying the effect of mood on skepticism and trust found that people in a good mood are more trusting and people in a bad mood are more skeptical. People in a bad mood were more likely to detect when someone was being deceptive, while people in a good mood were more easily fooled.

A recent study found that people can "catch" happiness from happy people around them or become more depressed if they're around people who are depressed. "People’s happiness depends on the happiness of others with whom they are connected," the authors concluded.

Studies have shown that exercise can help create new neurons in the brain, boost blood flow to the brain, and increase levels of key mood-regulating chemicals in the brain, such as dopamine and serotonin.

A number of studies have shown that as people grow older, they generally tend to accentuate the positive. Researchers speculate that as people begin to realize that they have a limited number of years left, they make a conscious or subconscious decision to focus more on positive thoughts. Another possibility is physiological: As people age, a part of the brain associated with emotion is more likely to be activated in response to positive images and less activated in response to negative images.

Although it's true that smokers can feel irritable while they're trying to quit, a Brown University study found that smokers reported being in much better moods after they had successfully quit smoking. However, if they had been trying to quit but were unable to do so, they reported being in much darker moods.

According to a study in the Journal of Personality and Social Psychology, people in a good mood are more likely to be superstitious than people in a bad mood. Researchers speculate that happy people are more inclined to "follow their gut" -- even if it's not rational – since what they've been doing so far has been making them happy.

Numerous studies confirm that people's moods can be significantly affected by the weather. Sunshine is associated with good moods, and "spring fever" appears to be a real phenomenon brought on by warmer temperatures at the end of winter.

Seasonal affective disorder (SAD) is a mood disorder that most often occurs in winter but can occur any time of year. It appears to be related to the body's response to varying amounts of sunlight, so it tends to occur when days are shorter in the winter or in other parts of the year when it's unusually cloudy.

According to the National Institute of Mental Health, 9.5% of American adults suffer from mood disorders -- a category that includes depression, dysthymic disorder, and bipolar disorder. Anxiety disorders, a separate category, affect 18.1% of U.S. adults.

Depression is differentiated from normal mood changes by the extent of its severity, the symptoms, and the duration of the disorder. Consult a doctor if symptoms persist for more than two weeks or if they significantly impair your normal activities.