In days long gone people didn't know what a mental illness was, if someone acted strangely they were possessed by evil spirits. As science in medicine and advancement in the understanding of how the human mind works psychiatrists re-categorized the symptoms as mental illness and disorders. Spirits not withstanding these people were obviously psychologically disturbed.
The human body is made up of physical=body, mental=mind, spiritual=soul. The mental or mind is the physical aspect of the soul. It is who we are, our personalities and thoughts yet the spiritual energy of the body supports the soul. When the physical or body is gone the soul and spirit still exist. Each part of what we are made up of requires certain things in order to maintain a proper balance. If any part of our makeup is not correctly maintained an imbalance occurs. We feel these imbalances in certain ways known as symptoms.
The medical and scientific world have finally realized the body mind and spirit all resonate in certain frequencies. By subjecting a person to certain frequencies of light, color, sound and EMF you can affect the balance between the body mind and spirit of a person. You can temporarily throw a person out of balance. If a person is continually subjected to certain input they can be permanently affected and changed.
You can expand on these things by the kind of things people feed upon. You've heard the saying we are what we eat? What we eat goes into our bodies and affects our physical health, but what we feed our minds and souls affects who we are as a person. If a person watches "soaps" all day long you can expect them to be a certain kind of person. If a person feeds on barbaric behavior like brutal sports you would expect them to be less mental and more of a physically oriented person. If people watch more scientific, educational and informational programs we know these people actually desire to better themselves and move to a more intellectual level. We know these people desire to understand creation, who we are and the world we live in.
The kinds of music we listen to is also frequency based and originates from and corresponds to certain physical and spiritual frequencies. Certain kinds of music and rap are mentally and spiritually harmful and can eventually change the frequencies a person resonates at. Rap is usually aggressive and harmful. The rhythm is like being punched repeatedly. Hate music and lyrics stimulate barbaric behavior and is harmful to body, mind and spirit. Other kinds of music have calming effects over the body mind and soul and it's not difficult to tell the difference. If a person takes enough bad crap into themselves it is clear that bad energy will be given off by them.
Things can be taken into the body that alter the body enough to affect the mind and spirit. Likewise things can be taken into the mind and spirit that alter the body.
To comprehend these things you need to understand who God our Creator is and what He intended of his people. The thing you need to understand here is the human body, spirit and soul were unique and they had to remain unaltered by certain external forces. Since Adam and Eve the human's had been altered by "the fruit of the tree of good and evil." In order to restore the children of Adam and Eve to the Father's Kingdom they had to be altered again by the Creator's own spirit. Once their spirits had been altered by the "fallen angels" they could never be restored to the Father. The reason being their spiritual frequencies had been altered in such a way the Creator couldn't bring them back on frequency. In order to understand how this works you must also understand how the Creator intended to restore and redeem human kind. He intended to do so by being born in the flesh Himself, living then dying and joining his spirit with those human souls who would be redeemed. He mixed His own spirit with human spirits in order to mix His spiritual signature with theirs so the Father spirit would recognized them as being His Children. The Creator could not be born to a woman who had been altered by the "fallen angels." The spirit of the Creator can not join with the spirit of a fallen angel (cursed) or a human / mortal being who's spirit has been altered by the fallen angels.
Anyone who has any understanding of how frequencies and electronic devices work know there's only certain combinations of components that allow transistors to resonate at certain frequencies. If any component is altered from specifications the unit component will cease to function properly. The human machine is no different. It must be created, serviced and tuned correctly. If any part of it goes out of tolerance the entire unit will not function correctly.
When you can peek behind the scenes to see what energy is behind such things you will discover there are spirits (spiritual energy) directly associated with all kinds of illnesses including mental illnesses. In order to gain a more in-depth understanding of how this works you should be aware that some non human spirits that cause illnesses can speak.
Spirits are energy, spirits project energy, people send and receive spiritual energy and it affects those around them. Positive energy can make sensitive people feel better and negative energy can literally make people sick.
Frequently when Jesus healed people he would tell them "Go your way and sin no more." There was a reason why he did this.
Because mental disorders are contagious at one time