The belief in fairies, fantastic and alien beings can be not only at mentally unhealthy people, but also at absolutely healthy, but fallen into a strange state at which they start seeing hallucinations.
Most often these people see fairies – tiny beings man's or female, growth from 10 to 20 cm. Vision is perceived as real, and even it is pleasant to much, but actually is only a hallucination. For the first time, this state was described in 1760 by the Swiss philosopher Charles Bonnet which name this syndrome received in medical practice. The nature of this phenomenon is not studied. Originally, emergence of hallucinations was explained with a cataract or glaucoma but as fairies seemed also to healthy people, this version was rejected. Most often visions arise upon sharp transition from light to dark space, or from long stay in the dark and loneliness, at concern in something.
Scientists build different hypotheses and guesses of an origin of this phenomenon. One of hypotheses assumes that there is it because of errors of a brain which, analyzing scanty visual information, creates the distorted images of the objects which are available in memory.
There are assumptions that constantly alarmed storyteller Hans Christiaan Andersen, suffered from Charles Bonnet's syndrome and quite could see the Thumbelina. It belongs to it the known statement that competently written down sick imaginations can become the beautiful fairy tale.