By Yasmin Rufo

Copyright bbc

Your body’s hormonal system also joins in the relaxation act.

Willis says that spending time outdoors triggers our endocrine system and lowers levels of cortisol and adrenaline – the hormones that surge when you’re stressed or anxious.

“A study found that people in a hotel room for three days who were breathing in Hinoki (Japanese cypress) oil saw a big drop in the adrenaline hormone and a large increase in natural killer cells in their blood.”

Natural killer cells are cells that tackle viruses in the body. The participants in the study still had elevated natural killer cells in their body two weeks after inhaling the smell.

Essentially nature “calms what needs calming and strengthens what needs strengthening,” is how Prof Ming Kuo from the University of Illinois at Urbana-Champaign, summed it up to the BBC.

“A three-day weekend in nature has a huge impact on our virus fighting apparatus and even a month later it can be 24% above baseline.”

Studies also show smaller but still persistent effects from shorter periods spent in nature, she says.