ANN ARBOR—Get out—for at least 30 minutes. The positive impact warm, sunny weather can have on mental health and mood are real, according to new University of Michigan research.

Taking a trip to someplace warm in the middle of winter or lingering outside when spring arrives can be especially beneficial, with pleasant weather improving mood, memory and broadening cognitive style (openness to new information and creative thoughts) as time spent outside increased, researchers found. Hotter weather during the summer, however, lowered mood levels and the effect of pleasant weather was far less noticeable in other seasons.

“Being outside in pleasant weather really offers a way to re-set your mind-set,” said Matthew Keller, the U-M post-doctoral researcher who led the psychology study. “Everyone thinks weather affects mood but the biggest tests of this theory in 2000 found no relationship, so we went back and found there are two important variables: how much time you spend outside and what the season is. If you go from winter to spring and spend enough time outside, there’s a noticeable change.”

The findings, completed by a team that also included U-M social psychology professors Barbara Frederickson and Oscar Ybarra, will be published in an upcoming issue of the journal Psychological Science.

A set of three studies involved more than 600 participants from throughout the United States. In one study conducted during the spring in Ann Arbor, participants who were randomly assigned to be outdoors during warm and sunny days showed improved mood and memory compared to participants who were outside when the weather was not pleasant and compared to participants who spent the time inside.

The impact of weather on mood and cognition has been difficult to demonstrate because people in industrialized countries, on average, spend 93 percent of their time indoors, making them largely disconnected from the impact of changing weather outside.

Keller himself experienced the phenomenon and was inspired to conduct the research after leaving Michigan for a mid-winter trip to Mexico, quickly being reminded that “life is full of color and life is fun. It’s easy to forget that during the wintertime.”

He notes that most people feel a little more blue in the winter and better in the spring, with the most extreme example being among those who suffer from Seasonal Affective Disorder (SAD), a recurrent depression with typical onset during the fall or winter. Previous research has found a connection between hot weather and violent behavior, and sunnier weather improving stock performance.

The researchers also found the optimal temperature for mood for most Americans is 72 degrees, about room temperature, with mood decreasing if temperatures became significantly higher or lower. There were regional differences, however, with mood peaking at 65 degrees in Michigan and 86 degrees in considerably warmer Texas.

For weather to improve mood, subjects needed to spend at least 30 minutes outside in warm, sunny weather. Contrary to their initial expectations, researchers found that spending time indoors when the weather outside was pleasant actually decreased mood and narrowed cognitive style. They suspected this was perhaps because people resent being cooped-up indoors when weather becomes better in the spring or perhaps because improved weather can make normal indoor activities feel boring or irritating.

The researchers note that it should not be surprising that weather and seasons affect human behavior, given that humans have evolved with seasonal and weather changes since the dawn of the species.

Calling for further research into the subject, the researchers offer a straight forward prescription: “If you wish to reap the psychological benefits of good springtime weather, go outside.”

For more on Keller, visit: http://www.umich.edu/~psycdept/emotions/mckeller.htm

For more on Fredrickson, visit: http://www.lsa.umich.edu/psych/people/directory/profiles/faculty/?uniquename=blf

For more on Ybarra, visit: http://www.lsa.umich.edu/psych/people/directory/profiles/faculty/?uniquename=oybarra