The classic carol claims that “it’s the most wonderful time of the year.” But for some, the holidays are a time of melanholly, a.k.a. the holiday-season blues (as dubbed by last week’s issue of the New York Times magazine). And those moody feelings could end up costing you more than a gift-buying spree at the mall.

New data from Harvard and Columbia University has found that feelings of sadness can cause you significant financial loss. Participants in a recent study that watched a video which induced feelings of unhappiness and impatience made financial decisions that earned more money in the short-term—but then had smaller, overall gains over a longer three-month period of time. Researchers concluded that depressed feelings can cause people to seek instant gratification with their spending and investments.

The next time I’m feeling down, I’m going to keep this in mind and make sure that I reach for a cookie or turn on some mood-boosting music—instead of reaching for my wallet.