A new study finds that people who take a 90-minute walk in a natural area — the woods or a park, for example — compared with similar strollers in high-traffic urban areas displayed decreased activity in a part of the brain associated with a key factor for depression.

"These results suggest that accessible natural areas may be vital for mental health in our rapidly urbanizing world," said study co-author Gretchen Daily of the Stanford Woods Institute for the Environment. "Our findings can help inform the growing movement worldwide to make cities more livable and to make nature more accessible to all who live in them."

More than half the world's population lives in urban areas, an estimate expected to rise to 70 percent over the next few decades. Experts say city dwellers have a 20 percent higher risk of anxiety disorders and a 40 percent higher risk of mood disorders than residents of rural areas.

The study asked participants to take a walk through grasslands and woods or along a major, heavily used roadway. They found little physiological difference between the two groups, including with heart and respiration rates, but noted reduced activity in the brain's subgenual prefrontal cortex — a region active during rumination, i.e., repetitive thoughts focused on negative emotions — in the group that walked through natural areas.

Body of Knowledge

After age 30, the brain begins to lose neurons at a rate of about 50,000 per day, shrinking 0.25 percent in mass each year. Think about that on your next nature walk.

Life in Big Macs

One hour of sitting or singing in church burns 102 calories (based on a 150-pound person), or the equivalent of 0.1 Big Mac.

Doc Talk

Distal pulse: the pulse farthest from the heart.

Phobia of the Week

Kopophobia: fear of fatigue.

Never Say Diet

The speed-eating record for watermelon is 13.22 pounds in 15 minutes, held by Jim Reeves. Note: Most of these records are held by professional eaters; the rest are held by people who really should find something better to do.

Observation

"When I'm not in my right mind, my left mind gets pretty crowded." — American comedian Steven Wright

Medical History

This week in 1933, Dr. W.F. Reinhoff Jr. performed the first successful lung removal operation (extirpation of the lung), in Baltimore. The lung was cancerous. The first human single-lung transplant occurred 30 years later.

To find out more about Scott LaFee and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.