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The smell of the sweat you produce when terrified is not only registered by the brains of others, but changes their behaviour too, according to new research. It adds to a growing body of evidence that humans may communicate using scent in a similar way to how other animals use pheromones.

Lilianne Mujica-Parodi, a cognitive neuroscientist at Stony Brook University in New York and colleagues collected sweat from the armpits of first-time tandem skydivers as they hurtled towards the earth.

“People who are engaged in multiple enjoyable activities are better off physically and psychologically,” said study co-author Karen A. Matthews, Ph.D. She is a professor of psychiatry, epidemiology and psychology at the University of Pittsburgh School of Medicine.

The study appears online in the journal Psychosomatic Medicine: Journal of Biobehavioral Medicine.

For the study, 1,400 adults reported how often they participated in a variety of leisure activities, including spending time unwinding, visiting friends or family, going on vacation, going to clubs or religious activities or playing sports.

Adults with higher scores – indicating the most time spent in different leisure activities – had lower blood pressure, waist circumference, body mass index and cortisol measurements, all markers of good health.

“When one is under stress, the usual thing is to cut back on enjoyable activities because you're feeling uncomfortable and you need more time to deal with the stress. But these data suggest that is the wrong thing to do and that continuing enjoyable activities you do can be helpful,” Matthews said.

People who spent more time doing diverse leisure activities also reported stronger and more diverse social networks, more feelings of satisfaction and engagement in their lives and lower levels of depression. Those who logged the most leisure time also slept better and exercised more consistently, the authors say.

Other studies have examined the link between specific activities, such as exercise, and improved physical and psychological health, but this is the first to show that the accumulation of multiple sources of enjoyable activity benefits health, Matthews said.

The study outcomes add to what we know about the connection between body and mind, said Kathy Richards, PhD, a registered nurse and professor of health promotion at the University of Pennsylvania School of Nursing in Philadelphia.

“Although the amount of leisure time each person needs is highly individual, we all need to monitor our own bodies and stress levels and participate in leisure activities to have happy, healthy and productive lives,” Richards said.

Pressman SD, Matthews KA, Cohen S, et al. Association of Enjoyable Leisure Activities With Psychological and Physical Well-Being. Psychosom Med 2009 Jul; doi:10.1097/PSY.0b013e3181ad7978 [Abstract]

Shia Kent, from the University of Alabama at Birmingham, led a team of US researchers who used cross-sectional data from 14,474 people in the REGARDS study, a longitudinal study investigating stroke incidence and risk factors, to study associations between depression, cognitive function and sunlight. He said, “We found that among participants with depression, low exposure to sunlight was associated with a significantly higher predicted probability of cognitive impairment. This relationship remained significant after adjustment for season. This new finding that weather may not only affect mood, but also cognition, has significant implications for the treatment of depression, particularly seasonal affective disorder.”

Kent and his colleagues speculate that the physiological mechanisms that give rise to seasonal depression may also be involved in sunlight's effect on cognitive function in the context of depressive symptoms. Cognitive function was assessed by measurement of short-term recall and temporal orientation. As well as regulating the hormones serotonin and melatonin, light has been shown to also affect brain blood flow, which has in turn been linked with cognitive functions. The researchers write, “Discovering the environment's impact on cognitive functioning within the context of seasonal disorders may lead not only to better understanding of the disorders, but also to the development of targeted interventions to enhance everyday functioning and quality of life.”

The study was funded by the U.S. National Institute of Neurological Disorders and Stroke.

Kent ST, McClure LA, Crosson WL, et al. Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study Environ Health 2009 Jul;8:34 doi:10.1186/1476-069X-8-34   [Abstract | Full text ()]