In the 1990s, several children in Cleveland, OH, developed pulmonary hemorrhage (bleeding in the lungs). One of those children died. A preliminary study identified exposure to mold, particularly mycotoxins from Stachybotrys chartarum , as a possible cause of these illnesses. 23,24 On further review, however, the . Centers for Disease Control and Prevention (CDC) determined that the earlier analyses were in error and that the cause remained unknown. CDC also noted that a similar cluster of cases in Chicago was not associated with mold exposure and that pulmonary hemorrhage was not consistent with what is known of exposure to this fungus. 25
The placebo effect is related to the perceptions and expectations of the patient; if the substance is viewed as helpful, it can heal, but, if it is viewed as harmful, it can cause negative effects, which is known as the nocebo effect. In 1985, Irving Kirsch hypothesized that placebo effects are produced by the self-fulfilling effects of response expectancies, in which the belief that one will feel different leads a person to actually feel different.  According to this theory, the belief that one has received an active treatment can produce the subjective changes thought to be produced by the real treatment. Placebos can act similarly through classical conditioning , wherein a placebo and an actual stimulus are used simultaneously until the placebo is associated with the effect from the actual stimulus.  Both conditioning and expectations play a role in placebo effect,  and make different kinds of contribution. Conditioning has a longer-lasting effect,  and can affect earlier stages of information processing.  Those that think that a treatment will work display a stronger placebo effect than those that do not, as evidenced by a study of acupuncture.