How can I help my grumpy, anti-social 18-year-old child?

Dear Doctor;My 18-year-old is too cranky and grumpy. She is always complaining of depression and has even threatened to end her life before. She is anti-social, engrosses herself in novels and TV and has no friends. I’m worried she could be suffering from severe depression. How can I help her? Any kind of medication that could help? Disturbed Mother,53.