But Mackay wasn't drunk. As it turned out, her inner ear, the body's balance centre, had been destroyed by medication when she was hospitalized for over a month back in May 2005.
At the time, Mackay was diagnosed with a life-threatening infection in one of her ovaries, and so was put on a cocktail of medication, including an IV drip of gentamicin, a well-known, inexpensive antibiotic that is one of the few that hasn't fallen prey to antibiotic-resistant bacteria.
A few weeks later, the infection was almost gone when Mackay, still hospitalized, suddenly developed the bed spins and vomiting.
Her medical team told her she'd been laying down too long and gave her Gravol, but the symptoms didn't go away.
In a follow-up appointment after her discharge, Mackay was told that the dizziness was a side effect of the gentamicin, and that she would probably have to get used to it.
But she didn't discover the extent of the damage until later when neurotologist Dr. John Rutka assessed her condition and concluded that the gentamicin had essentially destroyed her vestibular system, the body's motion detector, located deep within the inner ear.
After a lengthy legal fight, Mackay eventually settled a civil suit with the suburban hospital that treated her. But nine years later, the spinning hasn't stopped, and Mackay lives with chronic vertigo, the constant illusion of motion.
Her balance is so unstable that she's been unable to get medical clearance to return to work with the City of Toronto, to a job she loved.
A professional hazard
Gentamicin ototoxicity, or poisoning of the ear, is just one way people end up with chronic vertigo. (Though it is one of the worst in that it can damage both sides of the inner ear.)
In the majority of cases, vestibular damage is the result of a virus. Head injury, autoimmune disease and genetic conditions are also culprits. As are some jobs.
Vestibular problems are a professional hazard for studio sound engineers, soldiers and military trainees who are exposed to bomb blasts, as well as football and hockey players, including Sidney Crosby, who develop chronic vertigo from vestibular concussions.
Even space flight has been implicated. Canadian astronaut Chris Hadfield acknowledged that life back on Earth, after five months of living on the International Space Station, came with dizziness and motion disturbances.
As he told one news organization, "your eye and inner ear are telling you different things."
In the U.S., the National Institute on Deafness and other Communication Disorders estimates that around five per cent of the American population, or roughly 15 million people, suffer from chronic vestibular problems.
There is no comparable Canadian figure, but the usual rule of thumb would suggest that amounts to about 1.5 million Canadians.
A 2009 study published in the Annals of Internal Medicine suggested that 35 per cent of all people aged 40 and older will experience at least some vestibular problems.
In fact, vertigo and dizziness are two of the fastest growing health search terms on Google, according to David Pothier, an inner ear specialist and researcher at Toronto’s University Health Network.
Unfortunately, says Pothier, "vestibular patients are often not taken seriously. They're repeatedly brushed aside as making up their symptoms. But what they experience is very serious and very real."
The patients who make it to Dr. Pothier's clinic in Toronto have spent, on average, two years bouncing around the health-care system looking for answers before they find him.
And they are among the lucky ones. There is a pronounced shortage of inner ear specialists, in Canada, and most vestibular patients don't end up under the care of a neurotologist.
As a result, their cases are often misdiagnosed as mental illness, and many are then prescribed tranquilizers.
But tranquilizers decrease brain activity, which in turn impedes the regeneration of the vestibular system. So patients on long-term prescriptions often get worse, not better.
Lisa Tanner, a 44-year-old former college track star from Atlanta, Ga., says that most of the physicians she's consulted "wanted to put me on Valium."
During a typical consult, Tanner says, she would be asked if she cries frequently. "I'm honest, I say yes because it's hard some days. I do want to just have a cry and then get mad."
But she also tells her doctors that she's not depressed. "I'm not happy about this, but I do want to get better."
Piecing together clues
Diagnosing the cause of dizziness and balance problems is notoriously difficult.
The vestibular system is really just a string of microscopic hairs at the end of cells, inaccessibly encased in bone, beyond the reach of biopsy or current imaging technology.
Accurate diagnosis requires both specialized equipment, which many health-care institutions lack, and specialists willing to invest inordinate amounts of time puzzling over patient charts and test results.
"You have to be like Sherlock Holmes," says Dr. Rutka. "You have to put all the pieces together, find all the clues."
Rutka, a leading international researcher and head of neurotology at the University Health network in Toronto, is the specialist who finally diagnosed Janice Mackay's problem.
For him, one of the rewards of his work is being able to tell these patients, "You're not crazy, you're not psychotic, you're not nuts. Forget what other doctors have told you."
The link to anxiety
But while patients with chronic vertigo are certainly not crazy, there is a complex and fascinating biological link between damage to the vestibular system and the development of anxiety disorders.
Ancient Greek medical texts noted the connection first, but a few millennia on we have yet to fully decode the brain circuitry that connects the two.
"It is difficult to prove, it's difficult to show. But I think it's almost certainly something that's there," says Dr. Pothier.
"When you want to comfort a child, you rock the child. When someone is upset, you rock them gently. People who are under extreme mental pressure often rock themselves."
If there is some kind of biological connection between movement and mood calming, then when the vestibular system — our internal motion sensor — is on the fritz, mood, it would follow, would also likely be affected.
What has been proven is that serotonin receptors, which play a role in mood regulation, exist in the vestibular system, and that there is some link between serotonin levels and vestibular regulation, according to the University of Pittsburgh's Dr. Carey Balaban, a leading researcher in this area.
"If you don't trust your balance system, anxiety is a natural protective process," he explains.
Vestibular patients' blogs and online groups are filled with discussion of anxiety and depression, especially, it seems, when there is little to alleviate the symptoms and patients are sometimes dismissed as fakers.
Joni Church, a 36-year-old video editor in Winnipeg, suddenly developed vertigo six years ago, the cause unknown , and describes struggling with "an inner despair where I felt like my life as I knew it was gone.
"The future for me was just sickness and the inability to do everything I love."
Most chronic vestibular disorders don't respond to medication, and there is currently no way to regenerate inner ear cells, though scientists are working on it.
About two-thirds of chronic vestibular patients do improve, although most will never be completely symptom free.
Essentially, these people learn through experience, and through rehab and behavioural therapy, to function as much as possible even when dizzy or off-balance.
Joni Church has recovered enough to return to work as a video editor, but it's a tough job for someone with a tendency to vertigo.
"It does make me a bit ill sometimes," she concedes, but she loves the work so she adapts her life around the condition.
Because her vestibular system has remained faulty, though, Church has been forced to relinquish a second passion: boxing. She was training for her first competitive fight when she became ill.
• Next: Rehab, the latest techniques for dealing with chronic vertigo