This has had me wondering…did some digging. Not sure if Canada has something similar in place but this is a referenced section from..http://www.additudemag.com/adhd-web/article/674.html
Essentially…we are screwed. It seems that a last ditch effort of telling your employer you have it when you are digging yourself out of a whole. You may get lucky and find one with some compassion…good luck with that! At least for me anyways….i am an engineer that works for engineers….engineers most times are just big old jackasses, well my experience anyways. 
The Americans with Disabilities Act, 1990
What have employers been told about ADHD and the ADA?
An article published by the New York Law Journal was not very encouraging. It says, “As more employees learn that their work-related problems may be attributable to Adult ADHD, some will likely seek protection fromdiscrimination under the Act. Employers faced with these disability discrimination claims should institute a two-pronged defense.”
“First, the employer should force the employee to meet his burden of proving that he does in fact suffer from ADHD, and that the employee’sADHD impairs a major life activity. If the employee successfully establishes that he is disabled within the meaning of the Act, the employershould argue that the employee is unable to perform the essential functions of his job. This argument will be aided if the employer can point to awritten job description stating that general skills such as following instructions, completing tasks on time and getting along with others areessential functions of the employee’s particular position.”
“The symptoms of Adult ADHD are such that they will likely prevent the employee from performing these essential functions. Therefore,employees who are terminated because of behavior attributable to Adult ADHD will probably not be entitled to protection under the Act.”
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