Mounting evidence points to physical activity as an excellent way to treat and prevent mental health problems. Physical activity seems comparable to psychotherapy for treating milder cases of anxiety and depression. Both anxiety and depression are common symptoms of a failure to cope with mental stress. According to the Canadian Psychiatric Association, as many as 47% of Canadians report being "severely stressed several times a week." Physical activity is therefore a welcome tool for coping with mental stress.

Anxiety
Anxiety is typified by a tendency to react to situations with worry, self-doubt and apprehension. Physical activity can help that. A single exercise session often leads to a reduction in anxiety, lasting from two to four hours. Relaxation, quiet rest or psychotherapy show similar improvements, but physical activity has longer-lasting effects. Some conditions apply:

• the activity must be continuous and rhythmical — what is commonly known as aerobic activity,
• the activity should be long enough to create mild to moderate physical stress in the individual. (This could be as little as one minute for people who have respiratory or heart problems.)

Anxiety can be situational (felt in a particular situation) or it can be a general predisposition (felt across many situations). Physical activity helps both conditions. Experiments using long-term exercise show anxiety reductions in generally anxious people, especially those with low to moderate anxiety. Anxiety levels decrease when individuals pursue a physical activity program for at least 10 weeks. Those who exercise for more than 15 weeks get the most benefits.

Depression
Exercise can also reduce depression. Depression is characterized by feelings of sadness, hopelessness, pessimism and a general loss of interest in life. People suffering from depression often become less depressed after doing aerobic activity for two to six months.

Exercise is not always good, however. Non-depressed individuals sometimes become depressed as a result of an "addiction" to physical activity. This occurs mainly in competitive athletes who undergo intense training, or overtraining. Overtraining results in the "staleness syndrome" in some cases. This syndrome is associated with decreasing performance and sometimes involves depression. When staleness occurs, rest is the best remedy.

Whether exercise is a plus or a minus for mental health depends on the dosage. Research is currently being done to determine the ideal intensity, duration, frequency and type of exercise required in treating anxiety and depression.

In the meantime, we know that exercise is mostly a plus for mental health. It can be used alone as a treatment for slight depression or anxiety, or in combination with other treatments for more serious emotional illness. What's more, it can be used to prevent anxiety and depression and to maintain a positive outlook on life.