You pulled an all-nighter — whether it be for your job or academics — and now you have to wake up early to attend class or commute to your workplace.

Or perhaps you are a new parent and you stayed up all night to soothe your crying baby.

Regardless of the reason for your lack of shuteye, you're probably thinking: what could possibly wake up a sleep-deprived brain? Maybe a cup of coffee or two, right?

It's not that simple. Although drinking coffee has long been a miracle-worker for the sleep-deprived, a new research has discovered that caffeine actually has little to no effect on a person after three nights of consistent restricted sleep.

Effects Of Caffeine On The Sleep-Deprived

Led by behavioral biologist Tracy Jill Doty, a team of researchers examined 48 people who got only five hours of sleep at night for five days in a row.

Twice a day, the study participants were given either a placebo or 200 milligrams of caffeine, which is equivalent to a big cup of coffee.

Neither the participants nor the researchers knew who got the placebo or who received the caffeine.

The participants spent one whole week sleeping at the lab and took either the caffeine or placebo at 8 a.m., again at 12 p.m. This went on for the entire week.

They took a series of tests related to wakefulness, sadness, reaction time and mood. They also took cognitive tests every hour when they were awake.

Findings showed that the group who took caffeine had faster reaction times during the first two days compared with the group who received a placebo.

But in the end, Doty and her colleagues found that all the participants had lower alertness and performance on the tests, even the ones who took caffeine.

Moreover, although the caffeine group reported feeling happier than those who took the placebo, it was only during the first few days of the experiment.

What's more, the caffeine group rated themselves even more annoyed than those in the other group over the final days of sleep restriction, researchers said.

Doty said the findings suggest that the same daily dose of coffee is not enough to boost performance after days of restricted sleep.

Why The Findings Are Important

The study, which is the first of its kind, is valuable because coffee is such a widely used stimulant to boost performance.

Doty said the new information is especially important for the military, because war fighters have restricted sleep and may also be drinking caffeine.

However, the study has its limitations: it did not take into account the fact that those who are sleep-deprived might increase their intake of coffee over time.

"We do not know what would occur if more caffeine was taken," said Doty. She said higher consumption of caffeine could result in jitteriness and other negative effects, but they have yet to find out whether or not a higher dosage would prevent decline in mental performance.

Details of the new study were presented at Sleep 2016, the annual meeting of the Associated Professional Sleep Societies.

What You Can Rely On

If we cannot depend on coffee too much after having insufficient sleep for too long, then what can we do?

Experts recommend snacking on energy-rich food, such as fruit or nuts, or even whole grain toast and baked beans.

If you are craving for high-fat and high-sugar comfort food, it's probably worthwhile to pass. These kinds of food may only leave you lethargic.

What's the best solution then? Go get some sleep. You deserve it.

Photo: Mike McCune | Flickr