What to do about a wrongful termination due to a major depressive disorder and PTSD?

You should speak with an employment law attorney--you may have a legal claim or you may not, depending on the specific facts. Both federal and New Jersey law prohibits discriminating against employees due to disabilities. However, not discriminating consists of making "reasonable accomodations," which are changes to how a job is done, or the provision of assistive devices/technology, if appropriate, that allow the employee to do the job, so long as the accomodations are not too expensive or disruptive. If the employee cannot reasonably do the job, even with accomodations, and/or presents too much of a liability or financial risk to the employer, the employer may be entitled to not retain him or her.

Also, an employee can be terminated (or a contract not renewed) for excessive unauthorized absences, so if you took more time than would be allowed under your contract, by your PTO, and/or under the Family and Medical Leave Act, if it applies to your employer (i.e. if your employer had at least 50 employees), then you could be terminated for doing so.

Therefore, whether or not the non-renewal of your contract is legal depends on under what grounds you took four months off, and whether you can do the job you were hired for. This are very fact-specific inquiries, which is why you need to review the situation with an attorney in detail. Good luck.