Psychologists Dr. Robert Emmons of the University of California at Davis and Dr. Michael McCullough of the University of Miami published a study in 2015 that looked at the physical outcomes of practicing gratitude. One third of the subjects in the study were asked to keep a daily journal of things that happened during the week for which they were grateful. Another third was asked to write down daily irritations or events that had displeased them. The last third of the group was asked to write down daily situations and events with no emphasis on either positive or negative emotional attachment. At the end of the 10-week study, each group was asked to record how they felt physically and generally about life.
The gratitude group reported feeling more optimistic and positive about their lives than the other groups. In addition, the gratitude group was more physically active and reported fewer visits to a doctor than those who wrote only about their negative experiences. (1)