Nine substances (and one sound) that can induce fear, anxiety and dread

So you want to terrify somebody. It's the kind of thing we all want, some of the time — and it turns out there are some substances (and sounds) you can use to do it fairly reliably. For your morbid edification, we present this list of fear-inducing chemicals, proteins, hormones, and frequencies.

Please do not actually try to use any of these. Especially the one where you beam a laser into somebody's brain.

Again, in case you didn't get it the first time: The science here is real, but the suggestions that you would actually turn into an evil mastermind and use any of these fear-inducers is a joke. I don't want to hear any stories about you using infrasound in your dorm, or feeding L-DOPA to your nemesis. So just cut it out.

And now, let's get scary.

1. Infrasound

Infrasound, or sounds below 20hz, are difficult for humans to hear but can still cause physiological effects and can make windows, doors, and other objects vibrate creepily. Some researchers have blamed infrasounds for hauntings, claiming that people feel "spooky" when exposed to these low-frequency sounds. Still, there is no definitive evidence that infrasound reliably makes people scared, though there are many anecdotal reports (including in scientific journals). Composers have even used the sound in their music to evoke feelings of dread, and the military has studied it as a weapon. So if you want to scare somebody, consider leaving them in a room where your speakers are pumping out a sound file below 20hz. They may feel like they've seen a ghost — or they might just notice weird vibrations.

2. Sweat

Smelling the sweat of a terrified person can cause you to become afraid as well. In experiments, researchers found that people inhaling fear-sweat from a nebulizer experienced elevated heart rates and activity in the amygdala and hypothalamus, parts of the brain associated with fear responses. Scientists believe people may be responding to pheromones in the sweat that communicate terror. These experiments were conducted by the military, you can imagine the potential applications for sweat-based crowd dispersal at your next Occupy Wall Street gathering. Just dust a crowd with fear pheromone, and let Scarecrow do the rest.

3. Noxious smells

Another smell-related fear reaction comes from humans smelling anything that is particularly noxious, especially in crowds. Fear and symptoms of illness like vomiting can zip through a crowd like wildfire when enhanced with disgusting chemical smells. A recent example of this came about five years ago when a meterorite smashed into an area in Peru, releasing noxious gas that smelled like sulfur. Thousands of people became physically ill, simply from smelling it — and then, as fear spread, people were getting ill just from seeing other people getting sick and smelling only a whiff of the gas. The military has long studied the fear-amplification effects of "malodorants." Probably the fear-sweat pheromone has something to do with this, but it seems that smelling something awful in a crowd can induce fear on its own. The lesson? If you want to create a stampede of freaked-out people, set off a really awful stink bomb in your cafeteria.

4. Dopamine

Usually we think of dopamine as the hormone that makes you feel all sexy and romantic. But if it seeps into the wrong part of your brain, dopamine will arouse feelings of terror and dread. In experiments with rats, scientists found that they could induce intense fear responses if they delivered dopamine to the back regions of the nucleus accumbens, a brain region associated with both emotional rewards and dread. The nucleus accumbens is a very small brain region, which means the difference between pleasure and terror is a matter of just a few millimeters.

5. Corticotropin-releasing hormone (CRH)

CRH is a peptide that acts on specific receptors in your brain to create what researcher Michael Davis called "a constellation of behaviors that look very much like fear and anxiety." He believes that over time, CRH can produce a general feeling of anxiety and dread. So if you want someone to have a general sense of dread and stress, CRH might be the substance you're looking for.

6. Channelrhodopsin (ChR), combined with lasers

Let's say that you're a mad scientist with a little time on your hands. You've got your victim in your grasp, and you want to condition them to fear cupcakes because that's just the kind of cruel, terrifying genius that you are. What you'll want to do is use a new technique called optogenetics — the manipulation of genes with light — to condition cupcake dread in your victim. First, you'll need the protein ChR, borrowed from some light-sensitive algae. This protein, when added to nerve cells in the brain, will allow you to activate those nerve cells using laser light. Now you're cooking with gas. Just add a little ChR to neurons to the nucleus accumbens, switch on your laser, and force your victim to stare at cupcakes. Repeat several times. Your victim is flooded with feelings of terror! It must be from the cupcakes, and not from the algae protein and lasers in their brain! At last your evil plan is complete. Your victim fears cupcakes.

7. Brain-derived neurotrophic factor (BDNF)

BDNF is a chemical that can help you cope with trauma and terror — but it can also solidify traumatic memories. In fact, researchers believe BDNF is probably related to "traumatic flashbacks," those super-intense memories of fearful events that will leave you quaking in your boots all over again. So if you wanted to use BDNF to induce fear, what you'd want to do is dose your victims with it while scaring the pants off them. They're guaranteed to remember you — with terror in their hearts.

8. Carbogen

Inhaling carbogen, a mixture of carbon dioxide and oxygen gas, is guaranteed to leave you terrified. This substance fools your brain into believing that you're suffocating, and thus induces all the anxieties associated with the fear of not being able to breathe. The gas can also leave you hallucinating, which is why experimental psychotherapists in the 1960s liked to use it on their patients to "open them up." Unfortunately, for every person who had an awesome trip on the stuff, there was another person who freaked out and thought they were dying.

9. L-3,4-dihydroxyphenylalanine (L-DOPA)

A chemical that's popular with bodybuilders, L-DOPA can act as an amphetamine. It's also used for treating Parkinsons and a few other disorders. But a common side-effect is intense anxiety, often associated with vivid, scary dreams. So if you want to give somebody nightmares, this would be your substance of choice.

10. Yohimbine

Like many substances on this list, yohimbine can have good and bad effects depending on dosage and the person taking it. Often used as an aphrodisiac, yohimbine can also evoke feelings of stress, anxiety, and downright terror. Further proof that from your brain's perspective, the difference between desire and danger is a pretty small one indeed.

Additional reporting by Sophie Bushwick.

Photo by Lukiyanova Natalia / frenta via Shutterstock