A few weeks ago I was having lunch with an old teacher of mine. He is a jolly Canadian man in his 60s, whose favourite topic of conversation is his many, many medical problems. He won't hesitate to tell anyone about his Hashimoto's thyroiditis, lumbar spinal stenosis, migraine headaches, peripheral neuropathy, or his various other aches and pains.

After filling me in on all the details of his most recent MRI scans, he said to me, "Now don't tell your mother, but I've also been getting some help from a homeopath lately." (My mother is his GP.)
"Oh really? What kind of help?"
"Well, I figured it couldn't hurt to try something alternative for this neuropathic pain of mine, I've tried so many other drugs."
"What did they give you?"
"Well, he's put me on these homeopathic drops. Just a couple on the tongue each night, and I tell you I've really noticed a difference."

I decided not to get involved in this one, and just made a non-committal "uh-huh" before asking about something else. I started wondering, though, whether it would have been right to argue the point with him. If he believes that his homeopathic drops, and not his gabapentin, are helping his pain, then should I argue?

You can probably tell that I am about to argue that I was right not to argue, but I have to confess that this is a special case. It's quite clear by now that his pain is not because of an underlying disease, it's just a symptom that he has to live with. If it were a serious, life-threatening condition that he was sprinkling water on, then this would be a different story. Or if he were seeing a homeopath instead of a doctor, rather than as well as several doctors. So my argument is restricted to only a subset of people who use those treatments that are probably just placebos. But I know there are a good number of people who do this—they go to their doctor, and then get themselves "centred" by someone who practices alternative medicine, without telling either of their healers that they are cheating on them.

With that disclaimer in mind, I think there are four possible ways a person might react if you tell them their placebo is a placebo:

  1. They don't believe you.
    Nothing changes, but you tried. Maybe you haven't done any good, but you've done no harm.
  2. They stop taking the placebo.
    Their symptom will probably worsen slightly (at least when it's pain we're talking about1), making them worse off. They will save some money, but they were willing to pay for the placebo before they knew the truth about it, so they must have felt that the improvement in their symptom was worth the money. In total, you have worsened this person's life.
  3. They switch to a "real" drug.
    This drug was already available to the person before you spoke to them, so they would have decided that, on balance, they preferred the placebo2. Perhaps, though, they didn't know about the real drug, or they didn't know how good it was, or they were just prejudiced, and they will be better off now if they decide to start taking it. You might have improved this person's life.
  4. They keep taking the drug, knowing that it's a placebo.
    Knowing it's a placebo ruins the effect, so their symptom will get worse, but they're still paying for it. You have worsened this person's life.3

So we have four possible outcomes, only one of which holds the possibility of improving someone's life, and even then it's a maybe.

And the placebo might not be a tablet or a drop of water. Think of "relaxant" candles, Feng Shui, aromatherapy, and dream catchers. A woman who buys fake pearls, thinking they're real. Is it wrong to tell her she is wrong, when she enjoys wearing them? Even religion, in the eyes of many atheists, is a placebo, but is it better to try to prove someone wrong or to let them believe something that makes them happier?4 Perhaps that's a bad example, since it's not a situation where people generally choose between several alternatives, but I think you can see my point.

Still, a lot of people feel that it's wrong to let people use a drug that "isn't real". Perhaps it is something to do with the profit margins of the company that is making these pills out of sugar. The next question then is, Why is it so bad for this company to make a profit, regardless of what they're selling? They have shareholders and workers who make a living from it. Is it wrong to use aspirin because it's also cheap to make? I think that, in the end, whether or not you think it's wrong to reveal the "true" nature of the placebo depends on how much moral weight you give to the truth in itself, removed from any questions of utility.

  1. Pain seems to be the only symptom that placebos can help to ameliorate significantly, or at least that's what the research has found so far.
  2. Of course, markets aren't perfect and not everybody would have "chosen" to take the placebo rather than the real drug. But in economics, although it's very complicated to talk about the behaviour of a single person, it's quite a lot simpler to talk about people in bulk, where aggregation leads to populations adhering fairly well to the predictions of theories that assume that everyone is well-informed about the products they consume. So, in general, although some people will be worse off with their new knowledge, the population as a whole already knew what it was doing.
  3. This may not be true. Tem42 has alerted me to the fact that placebos appear to have an effect, even if the patients are aware that they are placebos, so this would be equivalent/similar to situation #1: http://www.scientificamerican.com/podcast/episode/placebos-work-even-when-you-know-10-12-23/. One more reason to let someone keep using them, it would seem.
  4. Eskimo: "If I did not know about God and sin, would I go to hell?"
    Priest: "No, not if you did not know."
    Eskimo: "Then why did you tell me?"