Nearly one in five adults in the United States, 43.7 million people, are affected by mental illness in a given year, according to the National Alliance on Mental Illness. These numbers suggest that, at some point, employers will have to deal with issues related to employees' mental health.

When it comes to dealing with mental illness in the workplace, employers and employees are caught in a catch-22 situation. The catch for employers is that they are responsible for the safety of their employees and the public, but are also obligated not to discriminate on the basis of disability. If they know that an employee suffers from a mental illness, they are obligated to ensure that the employee is not in a position to harm anyone, which in some cases may mean terminating the employee. Following the crash of Germanwings Flight 9525 in March, the media and many members of the public were quick to accuse Lufthansa Airlines of negligence for not realizing that the co-pilot was mentally ill. Whether the airline is at fault remains to be seen, but society (and often juries) are quick to judge when others' lives are at stake.

But if an employer prematurely takes action against an employee based on a mental illness, it could run afoul of the Americans with Disabilities Act. The ADA protects employees who have mental health issues that limit one or more substantial life activities, as long as the employee can perform basic job functions with a reasonable accommodation.