Dec 26, 2014 05:29 AM EST
Stress May Increase Desire for Reward but Not Pleasure
New research suggests that feeling stressed may prompt you to go to great lengths to satisfy an urge for a drink or sweets, but you're not likely to enjoy the indulgence any more than someone who is not stressed and has the same treat just for pleasure.
"Most of us have experienced stress that increases our craving for rewarding experiences, such as eating a tasty bar of chocolate, and it can make us invest considerable effort in obtaining the object of our desire, such as running to a convenience store in the middle of the night," ] Eva Pool, lead author of the study, said in a statement. "But while stress increases our desire to indulge in rewards, it does not necessarily increase the enjoyment we experience."
Researchers from the University of Geneva found that stress prompted chocolate lovers in an experiment to exert three times as much effort to smell chocolate than unstressed chocolate lovers, but both groups reported about the same level of enjoyment when they got a whiff of the pleasing aroma.
For the experiment, researchers recruited 36 university students, of whom 19 were men, who said they love chocolate. To induce stress, the researchers asked students to keep one hand in ice-cold water while being observed and videotaped. Another group immersed a hand in lukewarm water. Ten minutes before and 30 minutes after the task, researchers collected samples of the participants' saliva and tested them for levels of cortisol, a hormone involved in stress response. Following the stress conditioning, all participants had to press a handgrip for the chance to smell chocolate when they saw a certain symbol. The researchers measured the amount of effort participants invested for a chance to smell the chocolate, and asked participants how pleasant they found the odor.
"Stress plays a critical role in many psychological disorders and is one of the most important factors determining relapses in addiction, gambling and binge eating," researcher Tobias Brosch said. "Stress seems to flip a switch in our functioning: If a stressed person encounters an image or a sound associated with a pleasant object, this may drive them to invest an inordinate amount of effort to obtain it."
Previous research with laboratory rats supports the idea that wanting and liking rely on two distinct networks of neurons in the brain that can be activated independently, according to the study.
"Although the findings with rodents provide a novel explanation for the stress-induced increase of reward pursuits, to the best of our knowledge, they have never been demonstrated in humans," researchers said.
The findings are detailed in APA's Journal of Experimental Psychology: Animal Learning and Cognition.
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