Sounds like ‘placebo’, right? Exactly – the nocebo effect is basically placebo’s evil twin. It’s when a patient’s bad expectations about a treatment mean that the treatment has a more negative effect than it otherwise would have. Which is a very long sentence. To give you an example, if someone is given a list of nasty side effects which they then get after taking a placebo, then they’re suffering from the nocebo effect.
The word ‘placebo’ means ‘I shall please’, from the Latin ‘placeō’ (‘I please’). So ‘nocebo’ means ‘I shall harm’ from, you’ve guessed it, noceō: ‘I harm’. It was coined in 1961 by a doctor called Walter Kennedy who I can’t find anything else to say about at all, sorry.
The word ‘placebo’ has been around for much longer than its dark counterpart – there’s a theory that it comes from a medieval practice where mourners were paid to chant for the dead during evening prayers. Because this was seen as a bit of sucky-uppy to him upstairs, these hired mourners were called ‘placebos’.