Nocebo
noun /noʊˈsiː.boʊ/ — The opposite of placebo — expecting harm produces real harm
Definition
A harmless substance or procedure that causes harmful effects purely because the patient expects negative outcomes. The nocebo effect is the placebo effect's darker twin — proof that negative expectation, like positive expectation, can have real physiological consequences.
Beyond the definition
Nocebo is the frightening mirror of placebo — it reveals that belief produces harm as readily as benefit. The nocebo effect means that being told you will feel worse can make you feel worse. Words, expectations, and beliefs have real biological power.
Origin & history
Latin: 'I shall harm' — the deliberate counterpart to placebo ('I shall please'). Coined in 1961 to describe adverse effects caused by negative expectations rather than pharmacological mechanisms.
Example sentences
Illustrative sentences for learning, not verified community posts or sourced quotations.
Patients warned of side effects experience the nocebo effect — they're more likely to report them.
The nocebo effect explains why frightening diagnoses can themselves accelerate decline.
Nocebo reminds us that the mind can make us sick with the same power it can help heal.
How to use it
This entry uses a noun. Follow the examples for articles and singular or plural forms; not every noun takes “a” or “an.”
Choose “Nocebo” when the meaning fits your context: A harmless substance or procedure that causes harmful effects purely because the patient expects negative outcomes. The nocebo effect is the placebo effect's darker twin — proof that negative expectation, like positive expectation, can have real physiological consequences.
Synonyms
negative placebo effect, harm through expectation
Antonyms
Related words
Nocebo vs placebo
The nocebo effect occurs when a patient experiences negative symptoms due to a belief that a treatment is harmful. This is the counterpart to the placebo effect, where beliefs lead to positive outcomes. Distinguish between these based on the patient's reaction to expectations.
Word in the Wild
See how this word appears in life, language and stories.
Illustrative sentences and imagined stories for learning — not verified sightings, interviews, or sourced quotations.
Fictional scene
Fear of the Complex Maze
An adult stands before a towering stone maze with an imposing guardian figure.
The imposing figure and the threatening scale of the maze create a negative expectation. Much like the nocebo effect, the fear generated by the guardian’s appearance can manifest real physiological stress, as the expectation of a trap impacts the observer's reaction.
Image credit: Wordspun · AI-generated conceptual illustration
Questions about this word
What does "Nocebo" mean?
Nocebo is noun meaning: The opposite of placebo — expecting harm produces real harm. A harmless substance or procedure that causes harmful effects purely because the patient expects negative outcomes. The nocebo effect is the placebo effect's darker twin — proof that negative expectation, like positive expectation, can have real physiological consequences.
Where does the word "Nocebo" come from?
Latin: 'I shall harm' — the deliberate counterpart to placebo ('I shall please'). Coined in 1961 to describe adverse effects caused by negative expectations rather than pharmacological mechanisms.