We’ve all been there. It’s the middle of the day, the conference call is running long, you’re struggling to keep your eyelids open. You find yourself thinking fondly about all of the nap times that you took for granted in kindergarten. Is naptime something we should have left behind in elementary school? Or are there still benefits adults can reap by squeezing in power naps?

Are power naps good or bad?

The answer to that question depends on who you are. Children, the elderly and people who suffer from sleep deprivation all need naps, according to Harvard Health. However, voluntary naps are another matter.

Contrary to popular belief, naps are not just for the slothful. Many of the world’s greatest leaders including Winston Churchill, Albert Einstein, John F. Kennedy, Margaret Thatcher and Napoleon Bonaparte sang the praises of a good power nap.

Naps are good for most people according to Sara Mednick, a psychologist from the University of California – Riverside, and author of “Take a Nap! Change Your Life.” Her research suggests that a short, power nap can improve brain functions like memory, focus, and creativity.

“For some people, naps are as restorative as a whole night of sleep,” Mednick says.

Short-term benefits of power napping include:

• Sharpened cognitive skills
• Elevated energy levels
• Improved mathematical and logical reasoning
• Increased reaction time
• Improved motor skills

On the flip side, long-term, power napping can:

• Reduce stress
• Decrease the risk of heart disease
• Help in weight management

That’s right, naps can have an impact on our cardiovascular health. Daytime sleep can help cardiovascular recovery after moments of psychological stress – like the stresses of the workday. In fact, researchers have found that a 45-minute nap can lower blood pressure.

Napping isn’t for everyone

Before you start a napping revolution at the office, you should know that napping isn’t for everyone. Some people just don’t like sleeping during the day. Others have trouble sleeping anywhere but in their own beds. Some will be up until the crack of dawn if they even entertain the thought of taking a nap during the day.

There are also some negative side effects of napping, such as sleep inertia. That is the feeling you get when you accidentally nap for way too long and you wake up wondering what year it is. Also, if you suffer from insomnia or other sleep disorders, napping might make these problems worse.

In particular, individuals who suffer from insomnia should avoid daytime naps. The irony here is that naps are most tempting for this group of people. When insomniacs succumb to the temptation of a daytime nap, they will find themselves in the vicious cycle of daytime sleep and nighttime insomnia. This may worsen insomnia with some insomniacs finding themselves craving naps during the day and not feeling tired enough to sleep at night.

Another group that should be wary of naps are individuals who suffer from obstructive sleep apnea, especially those whose sleep apnea has gone untreated. When these individuals sleep without a CPAP machine, they are likely to experience apneas or periods where they stop breathing. If you have sleep apnea and long for a nap, sleep in your own bed where you can access your CPAP machine.

For those who suddenly feel like they need more naps and have no obvious reason for increased sleepiness, you may want to take a hard look at your regular sleep schedule. Are you having trouble getting a full night sleep? Perhaps you’ve had your mattress five years too long and it no longer supports your sleep habits. To aid in improving your sleep quality, you might consider adding relaxing elements to your bedroom, such as an essential oil diffuser, ambient lighting or a white noise machine – anything that improves your sleep quality.

Related story: How Aging Affects Your Sleep and What to Do About It

If there’s really no explanation for the sudden siesta craving, you may want to talk to your doctor. Often fatigue is indicative of a larger problem – it may be a condition, a less obvious sleep disorder, or simply unwanted side effects to a medication.

I’ve got my pillow ready. How long should I nap?

Most experts recommend power naps that last between 10 and 30 minutes. This time span has been shown to boost alertness and elevate your mood without slipping into that nasty grogginess from sleep inertia. Even a six-minute nap may improve memory. However, a longer nap that allows you to experience a full sleep cycle (90 minutes), is known for helping your brain process information and solve problems.

The biggest tip when it comes to napping is to wake up before the deep sleep cycle sets in or allow yourself enough time to get through an entire sleep cycle. When you wake up in the middle of REM sleep (aka the deep restorative sleep where dreaming takes places), you’ll often feel more tired than when you laid down, making it becomes difficult to wake up. This feeling is most common from naps that are 30 to 60 minutes long.

I have to put a nap on my calendar. When is the best time to siesta?

The key to picking the best nap “time” is to plan based on what your schedule allows.

 You’re probably itching for a nap around mid-afternoon – 2 or 3 p.m. It’s that time of day where you’re reaching for another cup of coffee (hint: a nap might actually do more for you than that caffeine jolt). This is also the time of day that is the least likely to mess with your nighttime sleep schedule. Your goal, alongside getting more energy in the middle of the day, should be to avoid interfering with your nighttime sleep as that can have adverse effects on your overall health.

If naps are out of the question for you, there are some alternatives to getting the energy boost you need that don’t include sleep or caffeine. WebMD recommends getting a dose of Vitamin D from the sun, taking a short walk to get your blood pumping, eating a piece of chocolate or doing some light stretching.

All in all, power naps can offer some great benefits for those of us who can fall asleep and wake up when the alarm rings in 20 minutes. Indulge in the tranquility of a daytime snooze knowing you’re doing your body good.