One in five Canadians will experience mental illness at some point and chances are good they'll be on the job when they do. "We often spend more waking hours at work than at home," says Mark Henick, manager of the Canadian Mental Health Association's Mental Health Works program. When, if ever, is it time to tell your boss about your mental illness?

Do I have to tell?
Unless the health and safety of others could be at risk—if you're a bus driver, for instance, and your medication makes you drowsy—you aren't required to divulge your condition. If there are symptoms or medication side effects that have an impact, like difficulty concentrating, you're entitled to reasonable accommodations to allow you to get your job done. You might need to come into the office a little later than your normal start time, or use noise-blocking headphones at your desk, for example. “But you still don't have to disclose any diagnosis, just the functional limitations you might experience," says Henick.

Are there downsides to divulging?
It's illegal for an employer to discriminate against, harass or demote you because of your illness, but that doesn't mean it never happens. "Not all workplaces are safe to disclose these kinds of problems," says Henick. "There are still a lot of misconceptions out there." Your boss may believe someone with bipolar disorder is unproductive, or that everyone should walk on eggshells around a co-worker with depression.

What are the benefits of sharing my condition?
"Speaking from personal experience, it can be extremely empowering to disclose that you’ve struggled and you're getting through it," Henick notes. "It's a bit of a flag for [your boss] to watch out for you."

It may also take a weight off your shoulders and she won't make assumptions—that you're insubordinate or lazy, for instance—because of symptoms like anxiety or sluggishness. "Most people are reasonable," says Dr. Stanley Kutcher, a psychiatry professor at Dalhousie University in Halifax. "If you're a good employee, an employer will do everything they can to keep you."

Where do I start?
See your health-care provider first, advises Kutcher. Be as specific as possible about your job duties and seek advice about accommodations that may work.

Next, book a meeting with your supervisor in a quiet place. Bring along a doctor's note if you're requesting job accommodations, as well as printouts that help explain your diagnosis. Then sit down and have a frank discussion in a calm and reasonable way. Be clear about what you need, says Henick. "Bring practical solutions to the table. Employers respond better to that kind of approach—you're doing half their work for them."

You could try one of these openers to start the discussion: "I haven't been at my best lately and here's why,” or: “I'm managing an anxiety disorder and I've been thinking about some ideas we can try that might help me here at the office.” Use words like "disorder," "medical condition" or "mental illness" rather than "problem" or "issue."

If your condition doesn’t impact your job performance, let your boss know that. Either way, it won’t hurt to remind him of the contributions you make to the workplace.

How do I handle an unsupportive boss?
Worried your supervisor just won't get it? That's another good reason to meet with your health-care professional before going to your manager—to remind yourself that someone's in your corner. Check in with your employee assistance program, if your company has one, or seek support from your human resources department, union steward or even a co-worker. "You can usually find an ally in these situations," says Henick. "Even in the most toxic of workplaces, there's usually someone you can find who's on your side who can help you through this."

What if I go on leave?
You and your health-care team may decide you need shorter or part-time work hours, or even time away from the office. If you've been on the job for at least three months, you're entitled to up to 17 weeks of sick-leave protection—meaning you can't be fired or demoted, and your workplace benefits will continue. Some workplaces offer long-term disability as a benefit, in which case you may also receive pay while you're unable to work.

Read more:
Body over mind: A new way to treat depression
The top 10 mental health myths