Stockholm syndrome is a proposed condition or theory that tries to explain why hostages sometimes develop a psychological bond with their captors. It is supposed to result from a rather specific set of circumstances, namely the power imbalances contained in hostage-taking, kidnapping, and abusive relationships. Therefore, it is difficult to find a large number of people who experience Stockholm syndrome to conduct studies with any sort of validity or useful sample size. This makes it hard to determine trends in the development and effects of the condition, and in fact it is a "contested illness" due to doubts about the legitimacy of the condition.