Illness is best cured with drugs. That assumption has prevailed since pharmaceuticals became widely available. But in recent years there has been a growing interest in alternative medicines, many of which employ mental or spiritual powers to heal the body. Now research into the biochemistry of placebos is showing that these remedies are not as wacky as they sound and that we are, indeed, capable of curing ourselves. [Find out more about the science of how you feel.]

In Suggestible You: The Curious Science of Your Brain’s Ability to Deceive, Transform, and Heal, Erik Vance applies the latest science to an exotic smorgasbord of alternative therapies, including acupuncture, hypnosis, and even witchcraft—many of which he tests on himself. (Suggestible You was published by National Geographic.)

View Images Courtesy National Geographic Books

Talking from his home in Mexico City, Vance, who trained as a biologist, explains why his childhood experience of Christian Science piqued his interest in the mind’s power over health, why placebos are particularly effective in treating Parkinson's disease, and why he asked a witch doctor in Mexico to put a curse on him.

You were brought up in the Christian Science faith, which claims to be able to treat illness with prayer. Is there any proof that faith healing actually works?

Wow, that’s tough! I was brought up in Christian Science, which, at its heart, believes that the world, including our bodies, is a reflection of our minds. So, if you change your mind, you can change your body.

Growing up in Christian Science I saw a lot of healings, which piqued and sustained my interest in this subject. I saw people who claimed to be healed of cancer, or a guy who cut off his toe and the toe grew back. But my hope for this book is not to prove or disprove these things I saw as a child.

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Do placebos and the power of the mind work? What I’ve found is yes, but not with everything. There are rules and conditions in which healing can be incredibly effective. Parkinson’s, chronic pain, irritable bowel syndrome, depression, anxiety, certain types of asthma, and autoimmune deficiencies are all very placebo-responsive. But cancer is not.

Christian Science, homeopathy, or other unproven alternative medicines may make someone feel better, but when it comes to curing a life-threatening tumor, that isn’t an appropriate place to be using these methods.

Is today’s interest in faith and spiritual healing part of a troubling new flight from science, like the anti-vaccination movement? Does that concern you?

I understand the fear of this technology and the fear of doctors. I didn’t go to a doctor until I was 18 years old. When you don’t understand [modern medicine] or are brought up not to believe in it, it is scary. But there are times when unproven medicine and faith-based healing is appropriate. And there are times when it is not. For me it doesn’t take away from the power of the mind to know that it’s not effective against mumps.

My kids have their shots, I have shots, and I’m so grateful for that, but you also can’t deny that there’s a lot of fear of these things. Telling someone they’re stupid doesn’t help change their perspective. You have to meet them where they are. I am a scientist, I’ve read the data, I understand how vaccines work and have full faith in them. Yet, when I watched my son get a vaccine shot, I also felt a lot of fear. We can’t help it. These things are visceral.

View Images A child receives a dose of oral polio vaccine at a clinic in Dhaka, Bangladesh. Photograph by Karen Kasmauski, National Geographic

Placebos have been particularly effective in the treatment of Parkinson’s disease. How do you explain that?

Parkinson’s is the perfect disease to talk about placebos. It is a chronic deficiency of dopamine, which is one of those brain chemicals that does a lot of jobs in our bodies. One of [dopamine’s] important roles is in reward processing: how we think about good things we might get in the future.

Expectation drives placebos. And dopamine is a chemical that’s very responsive to our expectations. Parkinson’s happens to be a deficiency in the very chemical that’s very important in placebo effects and rewards.

If you look at Alzheimer’s, which does not have a high placebo response, you start to see that there are rules at play when it comes to placebos. It’s not your brain magically doing all these crazy things. There are certain chemicals we have access to and others we don’t.

If placebos are effective, why is there such a taboo against them?

For a long time, we didn’t know they were effective. If you’ve never experienced a placebo effect or pain alleviation through hypnosis, it looks like it’s either magic or a crazy person.

On the flip side, if you have experienced it—if you took a crystal, rubbed it over yourself, and felt better—it’s hard to accept someone looking askance at you. This thing works; why are you telling me it doesn’t?

For thousands of years, it has been something we just do. Whether or not it’s appropriate or right is beside the point. This is who we are. We use expectations in our healing.

View Images A witch doctor in Catemaco, Mexico, performs a ritual to cleanse a man of evil. Photograph by Ronaldo Schemidt, AFP/Getty Images

One of the things you did to understand the subject was hire a witch doctor. Where do you find a witch doctor? Online? In the Yellow Pages?

[Laughs] I live in Mexico City, and down the street there is a famous market where all your supernatural needs can be taken care of. You can get coyote skins, snakebites and swords for healing ceremonies—everything you need!

I thought it would be this secret, black magic in a dark den, but they advertise right out front. Do you want black magic or white magic? Do you want me to curse someone or help you to get your ex-lover back? It was very easy! I was looking for a curse to try and understand the antithesis of the placebo, which is a nocebo: a negative expectation.

I also traveled to Catemaco, a town in Vera Cruz famous for its witch doctors. I met with one of the leading witch doctors there to try and understand what we call the theater of medicine—all the trappings that go into the healing practice, like the stethoscope and white lab coat. In different cultural contexts, those things change. What was interesting in Catemaco is that many of the traditional healers have adopted the theater of modern medicine. They wear lab coats, cut their hair short, and use long words, which gives them the "flavor" of what we recognize as conventional medicine.

View Images A patient is loaded into an fMRI machine. The machine is used to look at the brain's response to pain processing. Photograph by Erika Larsen, National Geographic

What takeaways are there for medicine—for the way we interact with doctors and they interact with us?

The message for the patient is that [alternative medicine] can be effective. But I do lay out some rules for when to do it and when not to.

One is, don’t hurt yourself. If you have a life-threatening disease, that’s not the time to play with expectations.

Don’t go broke. I’ve talked to many people who’ve spent their life’s fortune chasing after healings that were never going to happen.

The last one is, don’t harm the environment. If your placebo involves endangered animals, it might be a good idea to pick a different one.

Within those rules and within certain diseases, there’s a lot you can do. Just because it’s a placebo doesn’t mean it won’t work. This has been shown again and again in laboratories.

The message for doctors is the importance of being more empathetic and taking more time. You may be throwing away 30 percent of your cure just by having a poor bedside manner. If you do, you can’t be surprised if people go looking for other means of healing. The witch doctors, traditional Chinese medicine practitioners, and homeopaths I spoke to all understand this.

There is a chapter on false memories in your book. What do memories have to do with placebos and hypnosis and health?

It’s a very good question. The book is called Suggestible You because it’s about suggestion. There’s a lot of great science on placebos that is very exciting, but I wanted to take a wider view of suggestion. Somatically, false memories are part of this mix. It’s the same with hypnosis.

Hypnosis is a suggestion for the present. You’re walking through a field or flying through the air and you feel your pain drop away from you.

With placebos, it’s a suggestion for the future. When I take ibuprofen, I immediately feel relief, even though the drug doesn’t actually kick in for 20 minutes.

False memory, on the other hand, is a way of suggesting that something in your past did or didn’t happen. All these things change the way we perceive reality.

A great placebo scientist told me that reality is the wave of information from our bodies crashing into the wave of information coming from our brains. Where those two collide, that’s what we see as reality.

View Images Healing crystals are laid out on a rock during a winter solstice celebration at Stonehenge. Photograph by Alice Smeets, laif/Redux

After your exploration of the mind and the power of expectation, is there anything you do differently? Is there anything you’d recommend to readers?

I am much more comfortable with my own suggestibility. We all have things we do. For me, it’s fizzy drinks and eating garlic when I have a cold. You can call it an active placebo. I also try and change my thinking around aches and pains, and I have a lot more respect for the power that my brain has in changing my health.

As long as you’re following the rules I lay out in the book, you can find your own place of self-trickery. For some people, it’s mysticism. For others, it’s cutting-edge technology. We all have the narratives that work for us.

I have tried a lot of alternative medicines and haven’t stuck with any of them. But I have a lot more appreciation for people who do find those things work and are able to tap into their placebo responses with help from an alternative therapist.

This interview was edited for length and clarity.