A nocebo effect is said to occur when negative expectations of the patient regarding a treatment cause the treatment to have a more negative effect than it otherwise would have. For example, when a patient anticipates a side effect of a medication, they can experience that effect even if the "medication" is actually an inert substance. The complementary concept, the placebo effect, is said to occur when positive expectations improve an outcome. The effect is also said to occur in someone who falls ill owing to the erroneous belief that they were exposed to a toxin, or to a physical phenomenon they believe is harmful, such as EM radiation. Both placebo and nocebo effects are presumably psychogenic, but they can induce measurable changes in the body. One article that reviewed 31 studies on nocebo effects reported a wide range of symptoms that could manifest as nocebo effects, including nausea, stomach pains, itching, bloating, depression, sleep problems, loss of appetite, sexual dysfunction, and severe hypotension. Etymology and usage The term nocebo (Latin , 'I shall harm', from , 'I harm') was coined by Walter Kennedy in 1961 to denote the counterpart to the use of placebo (Latin , 'I shall please', from , 'I please') a substance that may produce a beneficial, healthful, pleasant, or desirable effect). Kennedy emphasized that his use of the term nocebo refers strictly to a subject-centered response, a quality inherent in the patient rather than in the remedy". That is, Kennedy rejected the use of the term for pharmacologically induced negative side effects such as the ringing in the ears caused by quinine. That is not to say that the patient's psychologically induced response may not include physiological effects. For example, an expectation of pain may induce anxiety, which in turn causes the release of cholecystokinin, which facilitates pain transmission. Response In the narrowest sense, a nocebo response occurs when a drug-trial subject's symptoms are worsened by the administration of an inert, sham, or dummy (simulator) treatment, called a placebo. According to current pharmacological knowledge and the current understanding of cause and effect, a placebo contains no chemical (or any other agent) that could possibly cause any of the observed worsening in the subject's symptoms. Thus, any change for the worse must be due to some subjective factor. Adverse expectations can also cause the analgesic effects of anesthetic medications to disappear. The worsening of the subject's