A Canadian study is examining the use of an anti-psychotic drug to help anorexic patients gain weight.

The study, published in the online version of the American Journal of Psychiatry, was conducted over five years at an Ottawa hospital.

Dr. Hany Bissada, a psychiatrist at and director of The Ottawa Hospital Regional Centre for the Treatment of Eating Disorders, administered the drug olanzapine to a study group of 38 anorexic women aged 18 to 55.

Bissada says while schizophrenic patients suffer from delusions, those suffering from anorexia experience a very strong obsession "almost like a delusion."

Weight gain is one of the documented side effects of the olanzapine medication and Bissada says it appeared to help speed weight gain in the anorexic patients. He is now hoping to expand the study to a group of at least 500 patients.

Another side effect that proved useful in the study is the medication's calming effect.

"We found the olanzapine was helpful in speeding up the weight gain, and it was helpful in reducing the obsession over weight gain," said Bissada.

But the most challenging part of the study, said Bissada, was finding a complement of willing participants.

"Anorexic patients are so afraid of gaining weight, and we're offering them a medication that will make them gain weight," said Bissada.