The Americans with Disabilities Act provides wide-ranging protections to disabled people, but a big part of the impetus behind it was to prohibit employers from engaging in discriminatory practices against employees and would-be employees. It is supposed to protect employees from not being hired or being fired due to disability.
Congress passed the ADA in 1990, but the United States Supreme Court limited its scope in a couple of decisions over the years since then. Essentially, the court restricted the kinds of illnesses and conditions that would be defined as disabilities under the ADA. So in 2008, Congress passed an amendment to the ADA that would define "disabled" more broadly.
Critics say that broadening the definition of disability has resulted in a flood of new lawsuits by employees or others alleging violations of the ADA. According to the Equal Employment Opportunity Commission, complaints pursuant to the ADA increased 50 percent between 2007 and 2012.
Under the ADA, employees are commonly considered disabled if they must use a wheelchair, if they're blind, deaf, have a learning disability or have certain kinds of mental illness. Under the ADA, the key to whether a condition or illness counts as a disability is whether it substantially limits "major life activities," such as walking, talking, seeing and learning. Employers must make reasonable accommodations for employees with qualifying disabilities, but employers often argue that an employee's disability doesn't really qualify.
Ultimately, the determination of whether an employee is disabled must be made on a case-by-case basis. It isn't always easy for an employee to prove that an employer has violated the act, and the law on the subject continues to develop. However, the core of the ADA's purpose still stands. Employees shouldn't have to be face discrimination simply because of a disability.
Source: CNN Money, "What's behind the surge in disability claims?" Jonathan A. Segal, March 6, 2013