Malls are equally packed with retail stores and coffee shops — and they might be onto something. New research found that people who consumed caffeine products, which include coffee, tea, soda, and energy drinks, were more likely to buy things on impulse, aka things you later regret buying because you don’t really need them.

“Caffeine, as a powerful stimulant, releases dopamine in the brain, which excites the mind and the body,” said Professor Dipayan Biswas, a researcher at the University of South Florida.

“This leads to a higher energetic state, which in turn enhances impulsivity and decreases self-control.”

The researchers investigated the relationship between caffeine consumption and impulse buying in the most natural environment they could find, in two shopping centers. They set up an espresso machine at the entrances of a large retail store in France and a department store in Spain, and handed free drinks to more than 300 shoppers, who had to share their receipts with the researchers upon exiting the store. Half the shoppers were offered a cup of coffee that contained about 100 mg of caffeine, while the other control group was given decaf or water.

Those who buzzed through the shopping aisles high on caffeine spent 50% more cash and bought nearly 30% more items than those that hadn’t had any caffeine. Their shopping list was also noticeably different, with those who drank caffeine buying more non-essential items, such as scented candles and fragrances than those in the control group. There was virtually no difference between the two groups when it came to buying utilitarian items, such as kitchen utensils or storage baskets.

Researchers also set up an experiment in the lab, this time involving online shopping and with similar results. Two hundred business school students were split in two — one group consumed caffeinated products, the other stayed away from caffeine for the day — and were then asked to choose which items they’d purchase from a list of 66 products.

The volunteers who had caffeine in their system were more likely to pick items that are regarded as impulse purchases, such as a massager, while the other group was more likely to get more practical items, such as a notebook.

Those who drink moderate amounts of coffee, meaning up to two cups daily or even less, were the most susceptible to impulse buying, whose effect becomes attenuated in heavy coffee drinkers. So if you’re the kind of person who jumps like a rocket after a cup of joe, it might be a good idea to stay away from stores and Amazon.com.

“While moderate amounts of caffeine intake can have positive health benefits, there can be unintended consequences of being caffeinated while shopping,” Dr. Biswas said.

“That is, consumers trying to control impulsive spending should avoid consuming caffeinated beverages before shopping.”

The findings appeared in the Journal of Marketing.