A study funded by the Spanish government and published in the PLOS ONE scientific journal looks at a type of "causal illusion" - specifically, the belief by many people that because they took a certain pill for an ailment and then felt better, that the pill caused their recovery.
The study refers to such alternative treatments, such as homeopathy, as pseudomedicines, since scientific studies have failed to prove that they have any effect on curing illnesses.
The study participants, Spanish university students, were presented with questions via a computer program. They were given case studies and asked whether they thought various patients' illnesses were cured by certain remedies.
The study authors found that participants were more likely to think that a psuedomedicine cured an ailment if the alleged remedy didn't come with significant side effects. Also, people tended to give credit to a remedy even if the ailment was minor and likely would have gone away on its own.
Participants were less likely to overestimate causation if a medication was described as having onerous side effects. Frequently used medicines were also considered more effective, as well as low cost ones. Because the ailments would probably have resolved on their own with or without the medicines, what the authors call "accidental coincidences" would become more frequent as more people became fans of a supposed antidote.
According the study's authors, "This feeds a vicious circle in which accidental occurrences of a desired outcome reinforce actions that are thought to produce them."
Simply put, people often turn to useless remedies because they are cheap and unlikely to cause serious side effects. These remedies proliferate because people mainly use them for minor ailments that tend to resolve on their own. However, due to the concept of "causal illusion," folks give pseudomedicines credit for their recoveries and spread the word, causing other people to use the remedies for similar ailments, even though they also would have gotten better with or without a pill.