If you’ve ever put in long hours studying for final exams or perfecting a presentation for a client, you’ve probably found yourself wishing for an extra jolt of brain power. Nootropics are often touted as a way to help with that. Nicknamed “brain boosters” or “smart drugs,” they’re typically substances that purport to improve brain performance.

This cognitive boost is meant to be above our normal baseline, explains Dr. Scott Small, professor of neurology and Director of the Alzheimer’s Disease Research Center at Columbia University. Different parts of the brain govern different cognitive abilities, such as memory, abstract reasoning, decision making, and speed of processing. Nootropics are intended to target these areas, he tells Fortune.

“So in theory, if you wanted to improve memory above baseline, you would have a nootropic that improves the function of that area, somehow cranking up its functional capabilities,” adds Small, author of “Forgetting: The Benefits of Not Remembering.”

But just how well do nootropics actually work?

What are nootropics?

Nootropics fall into three different classes of drugs: eugeroics like Modafin and Nuvigil meant to promote alertness, stimulants like Ritalin and Adderall prescribed to those with ADHD, and dietary supplements. Because the first two classes of drugs are prescription-based, they are only formulated for—and should be used by—certain individuals.

But anyone can try a natural nootropic supplement, which can include one or a combination of several ingredients. They have the potential to reduce anxiety, enhance your mood, increase productivity, heighten your energy, improve your memory, and sharpen your focus. Some of the most common ingredients include:

Lion’s mane
Rhodiola rosea
Ginkgo biloba
Ashwagandha
Panax ginseng
Alpha GPC
Caffeine
Citicoline
Phosphatidylserine
Huperzine A
L-theanine
Bacopa monnieri

You don’t always need to tap into the $9.2 billion brain health supplement market to get your fill of these. You can easily get a dose of caffeine with a cup of joe or drink some L-theanine, an amino acid known for boosting alertness, with a cup of green or black tea.

But you may not even need to turn to a drug at all, in Small’s view. He says nootropics “could be a drug, a pharmaceutical agent, a diet. It could be a behavior, like physical or cognitive exercise,” he says. At the end of the day, “it’s an intervention, behavioral or not, that improves your cognition above normal.”

Are nootropics actually effective?

Research is limited on the effectiveness of nootropics. A study published in the National Library of Medicine finds that most nootropics don’t have an immediate effect after a single dose and need to be used for a longer period of time to measure improvement. It also concludes that there isn’t enough research on healthy individuals in the field.

Small has seen positive effects of behavioral interventions in reviving someone’s memory that has slid down a little bit with aging, but he says this is more focused on boosting a cognitive decline back to the baseline, rather than exceeding the cognitive baseline.

“In the strict definition of nootropic I don’t think there’s anything that meets that criteria—that you either do something or take something and all your cognitive abilities rise like a tide,” Small says, acknowledging his definition of a nootropic may be a little more orthodox than others’. “People have been searching for it. I’ve been searching for it.”

Are nootropics safe?

Many products advertised as nootropic supplements haven’t been examined in terms of safety and efficacy, according to the American Medical Association. As with any drug, there can be side effects, such as insomnia, anxiety, allergic reactions, or interactions with medications.

Experts agree that when shopping for a supplement, you’ll want to consider whether the ingredients have been well researched, the dose efficacy, synergistic effects (some nootropics work better together), if the labeling is transparent, and whether it’s been tested by a third party.

Small says that if you’re going to try a nootropic, you need to do your due diligence. “Whether it’s a supplement or a drug, it’s a pill. And that you just never know.”

But if, for example, a young and healthy person is taking the GRE and looking to boost their scores, he says he wouldn’t recommend taking anything in good faith. It’s why he prefers behavioral interventions. “Anyone can do them, and anyone can access them,” he says. “They seem to be the safest and most effective.”

Physical exercise is one of his go-to recommendations. “From a neurologist point of view, the part of the brain for physical exercise clearly improves the hippocampus, an area of the brain that is important for memory, and the frontal cortex, an area of the brain important for decision making.”

He also suggests staying cognitively active, which can involve working on games and puzzles. And, in the middle of a loneliness epidemic, staying socially engaged is also important since depression can affect cognition. Sleep is, of course, critical in maintaining normal cognition, Small adds.

As he puts it, it’s “all good cognitive hygiene.”

More on nutrition and supplements:

The 5 best supplements for healthy aging, according to a longevity expert
It’s not 8 glasses a day anymore. Here’s how much water you should drink each day
Do turmeric supplements work? Experts say, yes, for 2 conditions
Does apple cider vinegar really help with weight loss? Here are the science-backed health benefits

Do nootropics really boost focus and memory? Experts weigh in on ‘smart drugs’