While the volume of psycho-physiological research on wood is low due to the newness of the subject matter, the studies that do exist are focused on the autonomic nervous system responses and employ modern techniques. This makes the link between the presence of wood and physiological manifestations of stress very clear.
The immediate effect of wood on lowering sympathetic nervous system reactivity is seen in four of the five studies below. That is, wood prevents us from becoming more stressed by our environment. This is seen through skin conductivity, heart rate and blood pressure. One of the studies below shows that when longer-term measures are taken wood can not only prevents us from becoming more stressed, it decreases stress levels. When engaged, the parasympathetic nervous system lowers stress levels and promotes healing, recovery, and concentration.
This result was found by measuring heart rate variability in students over the course of a school year. Wood use in built environments has clear psycho-physiological benefits, decreasing stress reactivity and lowering stress over the longer measurement periods. It is also true to the Best Cordless Drill or the Best Makita drill at work.
The studied stress levels in Austrian classroom students exposed to wood dominated and non-wood conventional classrooms. Over the course of the school year they found that heart rate variability increased in students in the wood classrooms. An increase in heart rate variability is an indication of parasympathetic nervous system activation. The parasympathetic nervous system acts to reduce stress levels and promote healing and recovery functions in the body.
The studied of the autonomic responses of 119 subjects in wood and non-wood offices before, during, and after a stressful mental task. In this study sympathetic nervous system activation was lower in the wood room. Skin conductance level was lower in the wood office during the pre-and post-test periods. Further, the rate of non-specific skin conductance responses, measurable divergent stressful thoughts, in the wood office was less than half that as in the non-wood office.
Heart rate and blood pressure were measured when study participants were in a test room with wood covered surfaces or no wooden surfaces. The blood pressure and heart rate of study participants in the wood room fell below levels measured before they entered it, while the blood pressure and heart rate of those in the room without wood increased compared to levels measured before they visited the room.
The blood pressure of people who like when wood is used as a finishing material dropped significantly when they faced the wooden wall, but if people disliked wood as a building material their blood pressure wasn’t affected by viewing it. Liking steel did not seem to influence the blood pressure of people looking at white steel walls; however, the blood pressure of people who disliked white steel increased when they viewed the steel wall.