[thebean11]

OP has no responsibility to share about their illness. In this case they are perfectly within their right to tell some half truth (wanted to spend time with my family, study x subject, burnout etc) and your company might be in some legal hot water if you fired OP in response to finding out they were ill during that time..

Frankly I think it's unethical, and shows a lack of empathy, to punish someone for hiding an illness from an employer.