Rowling created the dementors after a time in which she, in her own words, "was clinically depressed".
Ekrizdis is a minor yet pivotal antagonist in the Harry Potter universe. He was an immensely evil wizard who lived in the 15th century in medieval Britain, it is believed he was either the creator of the Dementors or that his insane experiments and torture caused the Dementors to first manifest.
J.K. Rowling's Experience With Depression Inspired The Creation Of Dementors.
Rowling has revealed that the Dementors were inspired by her own feelings of depression.
According to J.K. Rowling on Pottermore, Dementors were originally born from the darkness of the mansion that became Azkaban. Now, they breed with each other, producing mists of despair, as in The Half-Blood Prince: The Other Minister: “And they're [the Dementors] breeding. That's what's causing all this mist.”
IT WASN'T ORIGINALLY A PRISON
Well, that's because originally, Azkaban was a fortress built by the sorcerer Ekrizdis, who himself was a powerful and insane practitioner of the Dark Arts. Ekrizdis actually lured, tortured, and killed Muggle sailors there up until he died and the concealment charms faded.
Professor Lupin explains that Harry has more dark moments in his past than most people, so there is more pain for the dementors to drudge up.
In Harry Potter, Dementors first appear in The Prisoner of Azkaban and are described as dark, foul beings who “drain peace, hope, and happiness out of the air around them.” Rowling writes, “Get too near a Dementor and every good feeling, every happy memory will be sucked out of you.”
A theory posted on Reddit suggests Dementors were drawn to Harry because they could sense the piece of Voldemort's soul living in him. Harry is an “accidental horcrux”, created when the killing curse casted by Voldemort backfired, fragmented his soul, and sent a piece of it to Harry's body.
Harry has the most terrible memories of any of the students. They seem to focus on people who have worse memories in order to sustain them, as they wish to reduce humans to something “soul-less and evil” like themselves. Harry would be a very attractive target to them.
Get too near Dementor and every good feeling, every happy memory, will be sucked out of you.” This description of Dementors is a perfect metaphor for the symptoms of depression, which include feelings of hopelessness, anger, fatigue, a loss of interest in hobbies, and an intense sadness.
And the only reason the Dementors choose to follow Voldemort is because he frees them from their duty to Azkaban, allowing them access to the richer pickings on the mainland.
The Dementor is a metaphor for depression and also other types of anxiety such as sadness and fear. Accordingly, the Patronus charm is a symbol for the positive thoughts that you are required to think to be able to face your fears and make the Dementors disperse.
Dementors are born when there is so much pain and suffer in the air that it can materialise it's self. That means that most Dementors were created during the First and Second wizarding war or in the time of Grinwald's attacks in Europe. That's why Dementors can only be destroyed by the Patronum summoning charm.
Dementors aren't technically alive, like Boggarts or Poltergeists. JKR said, "You cannot destroy Dementors, though you can limit their numbers if you eradicate the conditions in which they multiply, ie, despair and degradation."
While indeed powerful, Voldemort fails to achieve the same level of success as Grindelwald. He also fails to show the same mastery over the dark arts. Grindelwald can conjure intense flame, withstand Voldemort's Legilimency, camouflage himself and handle dark magical creatures.
The Dementors made his inner feelings of hurt and abandonment come to life, along with bringing back his worst memories. As mentioned by Remus Lupin, Harry's true fear was fear itself, which the Dementors projected. The creatures forced him to feel the defeated mentality inside of him that he generally pushed down.
Behind the scenes. It is possible that chocolate is used to ward off the effects following meeting a Dementor as it has chemicals inside it that stimulate the release of endorphins, which are chemicals produced by the body to combat stress and pain; often leading to feeling of increased happiness.
The Dementor's Kiss has only been used as punishment in rare cases. Sirius Black was supposed to receive the Dementor's Kiss in 1994 after his escape from Azkaban, but he narrowly escaped from Hogwarts School of Witchcraft and Wizardry before the punishment could be administered.
Albus Dumbledore was one who had long disapproved of the use of Dementors as guards, not only because of the inhumane treatment of the prisoners in their power, but because he foresaw the possible shift in loyalties of such Dark creatures.
Dumbledore : A child's voice, however honest and true, is meaningless to those who've forgotten how to listen. Dumbledore : A word of caution: dementors are vicious creatures. They will not distinguish between the one they hunt and the one who gets in their way.
By June 1996, all of the Dementors of Azkaban collectively rebelled against their employers to join Lord Voldemort, who offered them more victims and free rein across the country. This aided the 1996 and 1997 escapes of Death Eaters from Azkaban.
Every time Harry is confronted with a Dementor, he hears the screams of his mother as she is murdered by Lord Voldemort. A horrific memory to hear... He hears this moment because Dementors feed upon happiness and cause depression and despair in anyone near them. They make people relive their worst memories.
Harry's godfather Sirius Black endured 12 years in solitary confinement in Azkaban for a crime he did not commit. By focusing on his innocence he was able to survive and escape the merciless Dementors, and would later narrowly avoid the Dementors' Kiss with help from his godson.
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.