It's not new anymore, but a study reviewed by Inc. this January may be particularly relevant for those of us about to celebrate Thanksgiving. During the study, people who wrote thank-you letters to others showed heightened levels of gratitude in general three months later. And, according to an earlier study from Harvard University, mentioned in this article, people who wrote down three things they were grateful for every day showed higher levels of optimism even six months later.
Researchers in the most recent study had their test group write thank-you letters and then scanned their brain activity in the weeks and months that followed. The increases in gratitude were not only observed in behavior, as when participants had a chance to "pay it forward" for a gift they had been given in the study, but also in the neural pathways that showed activity on scans and in their self-reported feelings and perceptions.
So, if you are feeling particularly down this Thanksgiving, make giving thanks a major focus of the holiday. It may tide you over in the months to come.