[Poison and nocebo--2 aspects of toxicology].

BACKGROUND: Erroneously it is assumed that drugs promote health exclusively by interacting with the organism through chemical or physical forces. However, placebo phenomena are omnipresent in patients who believe in the value of a treatment, be it medical or paramedical. Conversely, nocebo phenomena originate from fear of detrimental effects attributed to a putative poison. Thus, both drugs and poisons release two different messages, the one being physicochemical, the other psychosocial. The latter is fostered by the public opinion, and man is a sensitive receiver. TYPICAL NOCEBO PHENOMENA: Here some epidemiological examples of nocebo phenomena will be presented. Each society selects the matching nocebos, today mainly as chemical exposures from oecological sources such as environment, buildings, emissions and industrial products. THERAPEUTICAL APPROACH: Suspicion of nocebo should not hamper the search for chemical poisons. Anxiety and fear furnish the neurobiological and evolutionary basis of the nocebo phenomena. Hence behavioural and conversational therapy, supported by antidepressants if needed, should be tried. Unfortunately, most patients expect their psychosocial problems instead to be declared as chemical.