Work out that depression

The uplifting effects of long-term exercise in depression may be down to a single compound - phenylethylamine - according to researchers at Nottingham Trent University.

In April, Fernando Dimeo and colleagues at the Free University of Berlin published results showing that even patients resistant to antidepressant drugs can find their symptoms alleviated through regular exercise. In September psychologist James Blumenthal, of Duke University Medical Centre in Durham, North Carolina, reported how just three half-hour exercise sessions a week can be more beneficial in reducing symptoms of depression than the drug sertraline, a chemical cousin of Prozac.

Now, an independent pilot study published in the British Journal of Sports Medicine by Ellen Billett and her colleagues provides an important clue as to why exercise can have such an effective antidepressant effect. The findings might help in our understanding and treatment of depression as well as demonstrating another benefit for exercise, aside from the familiar physical health effects.

	Ellen Billett

The researchers studied 20 healthy young men of average age 22 who were asked to do about four hours of moderate to hard exercise every week, mixing aerobic and anaerobic activities. The team tested urine samples on their "day of rest", analyzing for phenylacetic acid, a by-product of turnover of the endogenous neurotransmitter phenylethylamine, involved in the brain's activity during exercise. Previous research has simply measured levels of phenylethylamine itself but the researchers believe their approach provides a more accurate assessment of the compound's activity in the body.

The next day, the men were asked to exercise on a treadmill at 70% maximum heart-rate capacity - an effective cardiovascular exercise level. Exercising at this heart rate is also thought to change one's mood. The volunteers were asked to rate how hard they felt the exercise had been, and once again phenylacetic acid levels in their urine were measured.

The phenylethylamine molecule. Click on picture to get molecule in ChemSketch format.

The team found that phenylacetic acid increased by 77% after exercise, although how much it rose after exercise varied considerably among the volunteers (from between 14 and 572% than on the day before in 18 of the 20 men). Three of the volunteers rated the exercise as hard, and the highest rises in phenylacetic acid were seen in two of them.

The researchers caution that many factors may be involved in the phenylacetic acid response to exercise. However, they point to the structural similarity of phenylethylamine to the amphetamine drugs as a possible cue to the "high" felt by runners, a phenomenon linked to natural endorphin activity in the brain.

British Journal of Sports Medicine, 2001, 35, 342.^*

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