Coffee is beloved by many, and now researchers have found drinking it can improve mood as the daylight hours decrease. A pan-European study funded by the Institute for Scientific Information on Coffee found that more than a quarter of adults experience depression and increased feelings of sadness as it gets closer to winter. Twenty-one percent say they become more anxious as the days grow darker, while 24 percent say they find it harder to concentrate, and 25 percent say the shorter days make them lose their motivation to exercise. Twenty percent of respondents say they drank coffee to improve their mood, with 29 percent saying they drink more coffee as the days get shorter to feel more energized, and 21 percent saying drinking the coffee helped with concentration. An analysis of existing data also found that 75 mg of caffeine every four hours can result in a pattern of sustained improvement of mood over the day, and that the scent of coffee may enhance working memory and stimulate alertness. Still, drinking too much caffeine can cause sleep issues, and in high quantities it can cause severe disturbances to the heart and nervous system.