The effect of hypnosis depends on the participant, says Dr. Kevin Parker, director of the psychology clinic at Queen’s.

“It’s not a game,” he said. “For a third of people I’d say it could have no effect at all. But for another third of people it can have real and powerful effects.”

The success of hypnosis depends on the subject’s particular skills.

“People can reject hypnosis because they don’t believe in it, but there are people who would dearly love to embrace it but don’t have the abilities to do so,” he said.

Individuals more capable of being hypnotized rely on visual learning skills, Parker said.

Visualization is an integral component to successfully undergoing hypnosis.

Any behavioural treatment or intervention is likely to have some adverse effects, Parker said.

“It’s hard to do something powerful without having negative effects,” he said. “If you take a medication you might get sick to your stomach.”

People who undergo hypnosis could experience headaches and notice an impact on memory, Parker said.

“Most people have things they don’t want to remember,” he said. “If all of the sudden something reminds us of that memory, it makes us uncomfortable.”

The outcome of hypnosis also depends on the intention of the hypnotist, which varies depending on the particular setting, Parker said.

“Stage shows are like reality shows where you try to embarrass people or get people to embarrass themselves,” he said. “In any kind of ethical treatment, you are trying to help a person achieve their own goals.”

People who are interested in seeing a hypnotist should ensure that whoever they see is professionally qualified, Parker said.

“It’s a well researched field, but I’d see a psychologist or psychotherapist,” he said. “They could be a physician or have other training, but they should be a member of a college of psychotherapists.”