A Toronto woman denied a flight to New York as part of a cruise trip wants to know how U.S. border agents knew about her history of mental illness.

Ellen Richardson says she was told by U.S. customs officials at Pearson International Airport on Monday that because she had been hospitalized for clinical depression in June 2012, she could not enter the U.S.

As a result, she missed her flight to New York City and a Caribbean cruise, for which she had paid $6,000.

"I was in shock. I was completely in shock," Richardson said Friday on CBC's Metro Morning. "I had no idea how that was relevant to my seeking entry into the U.S. for a holiday."

Richardson is also an author who published a book, Hope for the Heavy Heart, in 2008 about her struggles with depression.

On a website promoting the book, Richardson describes how she became paralyzed from the waist down after jumping off the Bloor viaduct in a failed suicide attempt in 2001. In the book, Richardson says it was one of three occasions when she tried to take her own life.

Richardson told CBC News that border guards referenced her 2012 hospitalization, and not her book, in denying her entry into the U.S.

At the time, Richardson was told she could only enter the U.S. if a doctor — not her own doctor, but one from a short list of others whom she had never met — signed a document vouching for her. She would also have to pay a fee of $500.

Richardson turned around and went home. Only later did she wonder how the agent knew her history in the first place. Richardson says she has been on several cruises since 2001, all of which required U.S. flights, with no problems.

"It really hit me later — that it's quite stunning they have that information."

Ontario privacy watchdog to probe case

U.S. border guards are allowed to bar anyone they deem a threat to themselves, others or their property. They have access to police records — including even uneventful encounters with officers — but medical records are supposed to be held in the strictest confidence.

Richardson's stay in hospital was preceded by a 911 call, placed by her mother, but she says police were never involved, just an ambulance.

She has hired a lawyer and turned to her member of Parliament, Mike Sullivan, for answers.

Sullivan says the apparent lack of police involvement makes Richardson's case especially mysterious.

"We don't know how deep the connection is between U.S. customs" and Canadian authorities, he said.

Ontario's privacy watchdog said reports that private health information is being shared with U.S. border services are of "grave concern" and she will investigate.

Information and Privacy Commissioner Ann Cavoukian said she will look into the matter to ensure that personal health information isn't compromised.

NDP health critic France Gelinas asked Cavoukian to investigate earlier this week.

Gelinas said she's been contacted by three people who have been denied entry to the United States based on their personal health history.

She said such information shouldn't be shared with anyone outside their health-care providers and doing so undermines the integrity of all health services in Ontario.

She adds Health Minister Deb Matthews owes Ontarians an explanation.

"A person's medical history is something that must remain absolutely confidential," said Gelinas.