They shouldn't even need to "do a study". This is common sense, and modern science acts like they're confirming some new finding.

The fact of the matter is that we live and sleep on slabs of concrete, we wear shoes with rubber bottoms, we walk all day on asphalt/concrete, etc.. Not only are we disconnected from nature, we're literally disconnected from earth. When was the last time most people's feet touched bare grass? When was the last time most people laid in the grass and took a nap, or just watched nature. Even when we're "in nature" we're disconnected from its energies due to our shoes.

Ever wonder why you feel so refreshed after a visit to the beach? Because the waves crashing produce positive ions which our bodies desperately lack. Everyone should get into nature. Touch a tree, touch some plants. Walk barefoot in the grass for 20 minutes. Research grounding.