It can be difficult to prove that you'll never be able to return to work due to mental illness. However, insurance companies will take certain factors into consideration and may pay out in some circumstances.
Insurers may look at the type of treatment prescribed, as well as how often you're having the treatment. Insurers can also defer the payment if you can't prove your condition is permanent or severe enough to warrant a claim. Deferral can last until all treatment options have been tried.