Laboratory Studies of Rodents Don't Always Generalize to Humans

The results of this experiment seem to contradict decades of research, so Dr. Peter Gass and Dr. Johannes Fuss, authors of the study, offer alternative explanations of the results. Rats, they remind their readers, do not necessarily experience anxiety the same way that humans do.

In a human being, finding a dark corner and hiding is usually a counterproductive behavior. In a rat, especially a rat living in a laboratory in which the investigator also keeps a pet cat, finding a dark corner and hiding may be an essential life skill. The changes to the hippocampus that seem to increase behaviors associated with "anxiety" may actually be beneficial to lab rats. They just would not be beneficial to humans.

Is there any evidence that exercise can increase anxiety in human beings, rather than reducing it?

There is unequivocal evidence that exercise reduces anxiety in humans who have a chronic health condition. In a statistical analysis of 40 clinical trials, University of Georgia at Athens researchers publishing their findings in the Archives of Internal Medicine calculated that exercise lowered anxiety and there was very high level of confidence the results of these studies were not due to chance, that is that 40 studies were not a fluke. Exercise programs for the chronically unwell lowered anxiety when:

• The participant in the exercise program had previously been sedentary,
• The state of anxiety had existed for more than a week,
• The exercise period was greater than 30 minutes, and
• The exercise program was conducted for at least 12 weeks.

The 20 to 40 per cent of regular exercises who are "addicted" to exercise, however, tend to suffer anxiety and depression on days they are unable to work out. People who are addicted to exercise tend to exhibit:

• Feelings of euphoria after completing a session (for example, the "runner's high"),
• A need to keep increasing the length of their exercise sessions to get the same emotional benefit,
• Difficulties in meeting personal, social, or professional obligations due to the amount of time spent working out, and
• Anxiety, depression, and poor judgment when unable to exercise.

This negative addiction to exercise is slightly more common in women than in men. Men who think of themselves as physically fit benefit from many cultural cues that suggest they are in charge, in control, and valuable people. These cultural cues are not as abundant for women.

And what about people who work out occasionally? At least in Finland, getting exercise 2 or 3 times a week seems to enhance emotional health. A study of 1,547 Finnish men and 1,856 Finnish women found that those who participated in 2 or 3 sessions of mild to moderate exercise every week experienced less anger, less anxiety, and less depression than those never exercised at all.