A Noecebo is an inert substance or treatment that appears to cause an adverse effect on a patient or participant although it has no known biological effect. Sometimes the Nocebo effect can be disastrous. An example of this was in a school in Tennessee, where a teacher asked if the students smelt something, before developing symptoms of Headache, Nausea and Difficulty breathing. Her students soon suffered the same symptoms and within a relatively short time, over 200 people were sent to the hospital, even though tests showed no biological component and searches for causes resulted in nothing.

After watching CGP Grey's video on the subject, I wondered, if a fake illness can spread through a Nocebo, could a plague? after all mind to mind is certainly quicker and more effective than other common transmissions like touch or water. On a theoretical medieval continent, could a Psychogenic Plague exist?

  • 1
    $\begingroup$ Assuming Earth, standard physics, standard human psych and science-based? $\endgroup$
    – Green
    Aug 29, 2016 at 12:10
  • $\begingroup$ What caused that incident in Tennessee? I haven't read about a psychogenic (bacteria?) nor really investigated about placebo and nocebo $\endgroup$
    – Skye
    Aug 29, 2016 at 13:27
  • $\begingroup$ @Green yes, all earth-like $\endgroup$
    – TrEs-2b
    Aug 29, 2016 at 19:35
  • $\begingroup$ Do the symptoms have to be physical/psychosomatic? If not, and we're talking about an "infectious" mental illness, then one could devise more or less any kind of "toxic meme" which could both spread and hurt people — like "anyone who is/has (insert personal trait) should feel deeply ashamed, and even consider suicide, and also you should make other people feel the same way" $\endgroup$
    – Toadfish
    Sep 7, 2016 at 4:34

2 Answers 2


In the sense of a 'plague'? No, a4android is right, that's not likely to happen (though it isn't impossible, the only difference between an illness and a plague is scale).

However, there are ways to get the effect you seek without bending things in the least. Let's say the noecebo that gets started comes with a self-reinforcing component? A poisoning of the mind, so to speak. All you need is for a few factors to be put in place.

BEAR IN MIND! This answer is based on the concept that a noecebo is purposely pre-planned and injected into its victims with full knowledge and intent to do so.

  • A plan.

So you want to create death and destruction on a grander scale? Let's see how to best do this. The 'virus' may or may not have directly lethal results, but it isn't impossible for this to happen. The mind is a powerful thing, all you need to do is make the mind believe what you are selling, and you can have said mind stop the heart, ergo: death.

  • A first victim.

Patient 0, as it were. You need someone that is not immune to such a concept, which is tested by starting them out with a much less severe variant. Once you have the first victim believing that you have that power over them...

  • The first 'spread'.

So you have your victim in your power. Bring out said victim in front of a crowd and carefully explain what is about to happen. Make sure these people are influential and preferably hard to convince. It makes for far more credible publicity afterwards.

Once they understand that they are 'already in your power', offer the victim the covert 'command' (i.e. the predetermined 'stop your own heart' command). Make it something commonplace, like snapping, whistling, or a common word. You want this to be widespread, after all.

  • Infect the town.

Now that you have your first spread going, it will start to attract more and more attention. People will start ranting and raving in the streets. Trustworthy people, people that can affect a wider audience for you. They will tell their stories, they will say what you did and what they believe you are capable of. In their panicstricken state, they will not realise they are doing your work for you.

If you set it up right, others will start to believe it's true. That will do one of two things: either they will believe they have it too, or they will start to try to preemptively cull those they believe that are infected to 'stem the spread'. Now that the one town is in utter anarchy, you need to:

  • Spread the love.

While the media starts covering your ground zero, you go and start the same process in another town far, far away. Repeat the abovementioned steps a few times, let this become an utter frenzy. More and more people that are susceptible will believe they have it, and more and more people who aren't will fear they might be the next victim.

  • End result?

Well, either they 'cull the infected', or the 'infected' spreads the 'disease' more and more. If at any point you notice that the spread is slowing, repeat above mentioned steps until either you are caught (which can be planned for and thwarted if you are creative) or until you get the result you are aiming for.

And when things are at their darkest, you can come in as a knight in shining armour. Offer a sugar pill, using the placebo effect to stave off the worst of it. Just be sure to charge exorbant prices, and 'run out' often enough that they'll become even more desperate when you decide to sell.

Things to bear in mind:

  • I am not an evil person. I'm just misunderstood.

  • This is based on mob mentality, which is quite effective in the right circumstances. Just look at the Y2K bug for a very unsettlingly real example.

  • Whether you use a substance to 'infect' patient 0 or the first crowd is irrelevant. That's the slight of hand to get the effects you want.

  • Do not credit me in your master plan. If the CIA, FBI, Interpol, or anyone tracks me down, I can (and will) honestly say I've never met you.


The psychogenic effects are part of a spectrum of well known psychological effects related to susceptibility, beliefs, and mass hysteria. They are the basis of both the placebo and the nocebo effects as mentioned in the OP.

Psychogenic illnesses are well known phenomena. But psychogenic plagues are flatly impossible. Plagues are "epidemics with high rates of mortality." Our minds may make us ill, they may people believe they are suffering maladies and illnesses, but they can't kill us like a plague disease.

While forms of psychogenic death are known. Usually associated with witch doctors and kaidaicha men, but those are more like wasting diseases with the victims willing themselves to death. These are nothing like plague symptoms.

Psychogenic illnesses are possible and realistic, they have happened, but psychogenic plagues are impossible.

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    $\begingroup$ There have been cults which ended with all or most members killing themselves. You might argue that is a psychogenic plague with rapid burn-out, in the same way as Ebola before its most recent outbreak. $\endgroup$
    – nigel222
    Aug 29, 2016 at 14:50
  • $\begingroup$ Also there is the insanity that is IS or Boko Haram. To me they look.more like infectious fatal mental illnesses than anything else. $\endgroup$
    – nigel222
    Aug 29, 2016 at 14:54
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    $\begingroup$ Calling cults and political movements like Boko Haram pyschogenic infections as expression of your feelings about them is fine. I share those feelings too. But equating them diseases whitewashes the fact they are part of human nature. A part we would prefer to ignore, but it's there just the same. $\endgroup$
    – a4android
    Aug 30, 2016 at 6:10

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