Salaam, I have a friend who is suffering from jinn possession. Someone did black magic to her in order to destroy her and her marriage. She's now severely depressed, what can be done to help her?
Alaikumassalam wa rahmatullah,
As I explain in my answer Can jinns possess objects or show themselves? we must be extremely skeptical toward claims regarding jinns. Unless your friend has undeniable proofs that her depression is caused by jinns, we should assume it is just a medical condition.
This world is not a playground for jinns doing whatever they want to humans as some superstitiously believe. Their only power it seems is to inspire thoughts in humans, and even then their power is strongly limited by God’s protection of His believers. The Quran says:
30. Surely, those who say: “Our Lord is God,” and then remain steadfast, the angels will descend upon them: “Do not fear, and do not grieve, but rejoice in the news of the Garden which you were promised.
31. We are your allies and protectors in this life and in the Hereafter, wherein you will have whatever your souls desire, and you will have therein whatever you call for.” (The Quran, verses 41:30-31)
The Quran also says:
There are succeeding ones assigned to him; before him and behind him, protecting him by God’s command. God does not change the condition of a people until they change what is within themselves. And if God wills any hardship for a people, there is no turning it back; and apart from Him they have no protector. (The Quran, verse 13:11)
Imam Mujāhid b. Jabr (d. 722 CE) says in his interpretation of this verse:
There is not a servant of God except that he has an angel protecting him in his sleep and wakefulness from jinns, humans and natural dangers [hawām, literally meaning deadly and disease-causing animals and insects]...
Since the believers enjoy God’s protection and since jinns have so little power, we should always be extremely skeptical about claims of jinns doing things to humans. Such things are not impossible as far as we know, but they are extremely unlikely.
My recommendation therefore is for your friend to seek medical help for her depression. She can also read the Quran and do extra worship to be closer to God and enjoy His protection more, and maybe this will help reduce her fears of being possessed by jinns.