Is it possible for a person to hear the voices of jinn in their head and see them in the form of shadows or animals, or is that merely imagination and psychological disturbances?

The entry of jinn into the human body is affirmed by the Qur’an, the Sunnah, and the consensus of the Ahl al-Sunnah. However, seeing jinn in their true form is not possible, due to the Almighty’s saying: "Indeed, he sees you, he and his tribe, from where you do not see them." As for seeing them in other than their true form, it is possible. They may manifest in different forms, or their voices may be heard, or a jinn may enter the human body and speak with its tongue and voice.

However, one must distinguish between these possible cases and psychological conditions, delusions, or groundless whispers. A Muslim should not pay attention to such matters but rather occupy themselves with obedience, worship, remembrance of Allah, recitation of the Qur’an, and reliance on Allah. Through this, Allah will avert the plot of the devils from them.