How to tell between possession and mental illness?

When someone disbelieves in God, or worships stones or animals or politicians or priests, and perpetually commits sins and calls them good and calls good evil,
You can class them as mentally ill plus driven to delusion by satan, that's how
Satan is a jinn (spirit) and can electrically and chemically alter the delicate balance of the brain by throwing it off course, so you can't always be sure, it could also be the conditions around them, they may live among scorpions etc and get confused,
Or watch loads of tv which shapes the way they think and cause confusion with their fitrah (inherent nature) vice versa, but here are some sources from the Book

Sura 81 - At-Takwir (MAKKA) : Verse 22
And your comrade is not*mad.
Translation : Eng-Pickthal-Audio

Sura 37 - As-Saaffat (MAKKA) : Verse 36
And said: Shall we forsake our gods for a*mad*poet?
Translation : Eng-Pickthal-Audio

Sura 37 - As-Saaffat (MAKKA) : Verse 47
Wherein there is no headache nor are they*made*mad*thereby.
Translation : Eng-Pickthal-Audio

Sura 37 - As-Saaffat (MAKKA) : Verse 36
And (they) said: "Are we going to abandon our âlihah (gods) for the sake of a*mad*poet?
Translation : Eng-Dr. Mohsin

Sura 15 - Al-Hijr (MAKKA) : Verse 67
The inhabitants of the City came in (mad) joy (at news of the young men).
Translation : Eng-Yusuf Ali

Sura 54 - Al-Qamar (MAKKA) : Verse 47
Truly those in sin are the ones straying in mind, and*mad.
Translation : Eng-Yusuf Ali

Sura 68 - Al-Qalam (MAKKA) : Verse 2
Thou art not, by the grace of thy Lord,*mad*or possessed.
Translation : Eng-Yusuf Ali

Sura 68 - Al-Qalam (MAKKA) : Verse 51
And lo! those who disbelieve would fain disconcert thee with their eyes when they hear the Reminder, and they say: Lo! he is indeed*mad
Translation : Eng-Pickthal-Audio

Sura 15 - Al-Hijr (MAKKA) : Verse 6
And they say: "O you (Muhammad*SAW ) to whom the Dhikr (the Qur'ân) has been sent down! Verily, you are a*mad*man.
Translation : Eng-Dr. Mohsin

Sura 54 - Al-Qamar (MAKKA) : Verse 24
For they said: "what! a man! a solitary one from among ourselves! shall we follow such a one? Truly should we then be straying in mind, and*mad!
Translation : Eng-Yusuf Ali

format_quote Originally Posted by Keeya

If one works in the medical field, can you spot out the difference from a person being touched by a jinn from a schizophrenic or delusional person?

What are the signs, how can one know for sure if nobody can see them?

Dissociative Identity Disorder or Jinn Possession?
The main source of confusion arises from the fact that secularly and Islamically trained physicians do not work together, and so they often present very isolated views of what is happening. What complicates things further is that within each group, there are many disagreements about cultural differences in diagnosis; therefore, it is difficult to give a definitive answer. It also depends on how Islamically aware the psychiatrists are themselves. So, the picture at the start is unfortunately not very clear. In sha 'Allah, I will try not to be too theoretical and with the help of our scholar, we will, in sha 'Allah, try and answer your questions as simply as possible.

Dissociative Identity Disorder
According to Theodore Millon, an expert on personality disorder (of which DID is one), dissociative disorder, in general, is a type of disorder which manifests by a fugue state ( that is an actual emotional dissociation from a given situation), characterized by amnesia / ‘forgetfulness’. Some believe that dissociation is a symptom of a wider disorder whilst others see it as an isolated defense mechanism (i.e., a way to protect yourself from a harmful situation). In Dissociative Identity Disorder (DID), there is a failure to integrate traumatic experiences in to one integrated self. This means that the person may deny being present in a situation in which he/she is physically present, because being there was emotionally too traumatic for him/her to deal with. (The trauma has been commonly identified as some sort of abuse). The way the individual dealt with it at the time was to dissociate from himself/herself. In order to integrate the experience at an unconscious level (because it is too traumatic), he/she may actually take on characteristics of another personality in order to deal with the situation in a more effective manner (based on either real or fictional characters, male or female). These different personalities may allow the person to express feelings, actions and words that he/she may otherwise not feel able to. This difference in personality may continue long after the original trauma until it is resolved. This doesn't mean that the person is never himself/herself and can never recover, re-integrate himself/herself into an emotionally - stable individual. Cases of dissociative identity disorder are extremely rare.

Jinn Possession
To understand jinn possession, it is important to remember that Allah has created man and jinn, and that religion and religiosity within jinns are as diverse as they within humans (i.e. many jinns became Muslim at the time of the Prophet (pbuh). You may like to read “Ibn Taymiyyahs essay "The Jinn" (translated by Bilal Philips). Ma sha 'Allah, it is excellent in its simplicity and will clarify many points for you. There, Ibn Taymiyyah sets out the existence and reasons for possession. He highlights that jinn possession is possible (and this argument is later evidenced by the late Ibn Baaz in the same book). He states that the cause of possession is not trauma or defense against trauma as with DID, but is usually due to:

a) Sensual desires on the part of the jinn,

b) Anger by the jinn because something wrong has been (unintentionally) done to them. He cites examples that, though, the human may be blissfully unaware of what he has done, the jinn feels the act was done intentionally, and the possession is a form of punishment by the jinn against the human. The difference is further accentuated by the more spiritual and supernatural aspects of symptoms which do not exist in DID.

My clinical experience is that both exist in reality and have slightly different symptoms and widely differing causes. The difference in classifications is subtle differences between symptoms, the cause, and the relationship to ‘supernatural activity’. These factors determine the illness. However, what complicates things is that some of the symptoms overlap and can, therefore, be seen as one and the same thing in certain instances. This leads to the obvious question; are dissociation disorders and jinn possessions two sides of the same coin defined by different cultural emphasis? It is hard to find a clear answer! I have had patients, Muslim and non – Muslim patients, where I have felt that jinn possession is the only viable explanation. I have also had patients (very rarely) where the dissociation has been a temporary defense against a trauma and has been resolved in therapy. Of course, the importance of the etiology lies in the form of treatment required; either a psychologist or an Islamically trained physician. (Muslim psychologists can combine both skills and offer treatment - but this is rare.)

It is common for people to confuse DID, schizophrenia and jinn possession. DID is confused with schizophrenia, because of its delusional aspects which are interpreted as dissociation. However, it can sometimes be subtly different and may not be the result of trauma, but some form of thought disorder. There is also confusion between schizophrenia and jinn possessions, mainly due to occasional references, although, obviously there is no evidence for ‘supernatural’ activity in the experiences of patients with schizophrenia. The difference here is clear since in the case of jinn possession, there is often clear a physical evidence, unlike schizophrenia.

Psychologically speaking, the impact of jinn possession on care-givers is significant (though I cannot say whether jinns may affect more than one family member at a time). However, both the patient and the care givers will suffer from this experience, as we all suffer from anything unpleasant. Whenever anyone in the family suffers from any long-term illness, there is always an impact on family dynamics. The question is whether it is acknowledged or not. Often, it is ignored and the disruption in relationships, which the problem has caused, goes unquestioned and worries are never resolved. After these effects, a therapy is usually needed. In my experience, patients require some input after this experience, since jinn possession is, in and of itself, a trauma. It has a psycho-spiritual aspect which makes the trauma harder to accept, since, of course, our everyday life is generally limited to a physical reality. A fear of the unseen is quite common. The patient can be afraid of himself or his family members, especially young children can become afraid of the person who was possessed. (This is also a common reaction with people when their relatives suffer from mental illnesses such as schizophrenia, and DID due to the negative press images). Remember, it is not easy to recover from being possessed by something you cannot even see, but it is as real as other human beings. This idea in itself is a lot to adjust to and can often leave patients afraid of the intangible. Furthermore, since so much of the world is intangible, they might carry with them a fear of re-possession, because they are not aware that they contributed to the problem in the first place. Ma sha 'Allah, I think the person treating your sister did well to refer to her a psychiatrist / psychologist for further treatment of remaining symptoms. This means, ma sha 'Allah, she/he is taking a holistic view of the problem and dealing with its existence and after – effects.

Source

How do you know if its jinn or just psychological problems like schizophrenia ?

Evil/Jinn Possession in reality- Sleep Paralysis

^A reply from a Muslim Exorcist who used to be on forums.