Coffee is delicious and gets you through those moments when your energy is flagging but you still have to perform. But let's be honest, it can also have serious downsides.

As top sleep researcher Matthew Walker noted in his eye-opening recent book Why We Sleep, caffeine latches on to a particular type of receptor in our brains, blocking a chemical our bodies produce to let our brains know we're tired. Drink too much coffee and this chemical builds up, which is why some people crash painfully if they don't get their fix. Late-in-the-day caffeine can make it hard to get to sleep and caffeine can also enable people to push their bodies way too far, resulting in damage from sleep deprivation.

In short, there really is such a thing as over-reliance on caffeine. But there is also sadly such a thing as stultifying 4 p.m. meetings and up-all-night babies. So if you're convinced that you're leaning too much on caffeine but your still need an energy boost, is there a safer, science-backed alternative for when another espresso just isn't a good idea?

Can't drink coffee? Then just think about it instead. 

A new study suggests there might be and it's 100% guaranteed to cause you no negative side effects. Why? Because it doesn't involve imbibing any substances at all. Simply thinking about coffee, researchers found, was enough to give you a lift akin to actually drinking a cup of coffee.

The study was simple. The researchers nudged participants to think about coffee either by having them come up with an advertising slogan for America's favorite morning beverage or by reading an article about it, and then tested their level of physiological arousal by measuring their heart rate or straight up asking them how alert they felt.

"Overall, the results showed that thinking about and being reminded of coffee increased participants' physiological arousal levels (whether self-reported or based on heart-rate), compared with thinking about and being reminded of tea, and in turn this greater arousal prompted a more literal, focused thinking style," says the British Psychological Society Research Digest blog summing up the results.

Hilariously, the researchers add that viewing a high octane clip from the movie The Fast and the Furious seemed to enhance the effect (while chiller films did not).

Caveats and cautions

Psychology research has been plagued with studies that failed to replicate when scientists tried to test their colleagues findings lately, so there is good reason to take this one result with a grain of salt. BPS has some quibbles with the methodology of the study too, and the researchers themselves call for further studies.

But other research has confirmed the idea that how tired we expect to feel actually impacts how we perform. Surprisingly, attitude matters when it comes to exhaustion. Plus, these caveats might seem pretty unimportant when they're facing a slog through a low-energy afternoon. If a nap or a cappuccino (or both) isn't in the cards, daydreaming about coffee (and then watching a clip of your action movie of choice as a chaser) certainly can't hurt.

And hey, science even suggests it might give you a bit of a lift.