Public health heavyweights such as the Centers for Disease Control and Prevention and the Mayo Clinic agree that, in the words of Mayo psychologist Kristi Vickers-Douglas, "There's substantial evidence that exercise can enhance mood and reduce symptoms of depression."
The mood-enhancing benefits of exercise are of particular importance to women, who suffer from depression twice as much as men, according to the National Institute of Mental Health.
Feeling unhappy is characterized by a specific pattern of thinking, and thoughts are chemical in nature, creating a neurochemical response in the brain that generates a particular mood.
Recent research shows that negative thoughts and images cause a measurable decrease in the neurochemical serotonin, responsible for feelings of comfort, pleasure and satiety. Lower serotonin levels can also lead to feelings of fatigue and inadequacy. Habitually pessimistic thinking creates drops in serotonin of longer duration, resulting in chronic moods of sadness, despair, anxiety, irritability and inability to enjoy activities that once used to be enjoyable.
Improving mood: Increased serotonin
Even moderate exercise has positive effects on serotonin levels. While the reasons for this are not clearly understood, the Mayo Clinic affirms that exercise "causes an increase in levels of certain mood-enhancing neurotransmitters in the brain."
Also, it seems that the longer the exercise lasts, the greater the effect on serotonin. For instance, marathon runners describe reaching a "high" after several miles, in part because longer-duration activities may allow more time for the mind to shift attention away from negative thought patterns toward more neutral or pleasant thoughts.
Not only does exercise boost mood for the short term, it may also have lasting benefits. A 2000 study by Duke University Medical Center showed clinically-depressed individuals following an exercise program made significant improvements in their mental well-being. Those who continued exercising maintained their results at a one-year follow-up assessment, and equally as encouraging, had a lower relapse rate than those taking anti-depressants.
Reducing anxiety: Decreased epinephrine, cortisol
Exercise has also been shown to lower the neurochemicals associated with anxiety, which often accompanies depression. Characteristics of anxiety include inability to focus, sensing that things are moving too fast, and feeling exhausted but unable to sleep.
While people with anxiety may feel wired, they're actually exhausted because of the high levels of epinephrine (also known as adrenaline) that cause anxiety. Another contributing factor to anxiety is the stress-related hormone cortisol. Research shows that exercise reduces cortisol and epinephrine, while increasing levels of feel-good endorphins.
Aerobic exercise performed at a moderate intensity seems the most effective treatment for anxiety. A study performed at The University of Missouri demonstrated that exercise intensities over 50 percent of V02max (about 50 to 70 percent of maximal heart rate) did not significantly reduce anxiety. In fact, some of the participants exercising at higher intensities experienced increased anxiety.
Although anxiety can make you feel like you want to train hard, making your workout a little easier actually lowers epinephrine and cortisol more effectively.
Another significant benefit of exercise-based therapy is the feeling of empowerment it provides, particularly for those who can use it to avoid taking medication. As Vickers-Douglas points out, exercise allows people to "take an active role in their treatment."
Claire Dorotik is a family therapist and consultant specializing in the psychology of wellness.