What would you say to someone if he/she told you they don’t know what’s real anymore in their life?

This would be possibly your closest friend who has been through excessive mental torment from various causes for many years. And now those causes have brought him/her to question their reality itself. Are the people she sees really there? If she were in a fatal car crash, would she believe she would really die?
What would you say to someone if he/she told you they don’t know what’s real anymore in their life?
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