Can the principle of permissibility of disclosing sins to specialists secretly—for the purpose of treatment—be applied to bad dreams, so that they may be disclosed to a specialist to facilitate mental health treatment?

Concealing one's sins is the default, and it is permissible to disclose them for an overriding benefit.

Bad dreams should not be narrated in detail, as they are from the manipulation of Satan or self-talk, and are not visions that require interpretation. The Prophet, peace and blessings be upon him, said: "A good vision is from Allah. So if anyone of you sees what he likes, he should not narrate it except to one whom he loves. And if he sees what he dislikes, he should seek refuge with Allah from its evil and from the evil of Satan, and he should spit thrice, and should not narrate it to anyone, for it will not harm him." He also said, peace and blessings be upon him, to someone who saw his head cut off: "Do not speak of Satan's playing with you in your sleep." Dreams are of three types: glad tidings from Allah, self-talk, and frightening from Satan.

Whoever is afflicted with disturbing nightmares may narrate them generally to a doctor or a ruqya practitioner, to deduce a psychological illness or a spiritual affliction. As for the dream interpreter, he has no concern with them because they are not visions to be interpreted.