This issue arises every so often.  An employee has a serious illness and is warned by her doctor that stress at work worsens the illness.  Is that a disability?  Not according to caselaw under the old (ie, pre-amendment) Americans with Disabilities Act.  In one case, the client was warned that her hypertension would worsen if her stress was not ameliorated.  She could suffer a severe heart attack, the note warned.  The stress was largely from work.  So, the doctor gave her a note to give to her employer with suggestions on how to reduce stress at work.  The employer ignored the note.  The employee filed suit and lost on summary judgment.  Caselaw interpreting the old ADA simply does not provide protection for a potential disability.  

A severe heart attack, said the judge, was a not a disability, yet.  Hypertension did not yet affect her daily life, said the court.   So far, the employee functions normally, other than loss of sleep.  So, she lost her lawsuit.

Another employee suffers from a rare genetic defect causing her spinal issues.  She has herniations in her neck and spine.  She has to stay home every so often and take medication.  She misses work, apparently without warning and her employer complains.  They start referring to her as the "absent" employee.  The stress causes her spine to worsen, causing even more time off.  Under the new ADA, that condition might constitute a disability.  

We had a saying when I served in Iraq, "nothing is easy in Iraq."  Well, nothing is easy in employment law.