From Wikipedia there you find many references: "Sadism involves deriving pleasure through others undergoing discomfort or pain. The opponent-process theory is one way to help explain how an individual may come to not only display, but also enjoy committing sadistic acts. Individuals possessing sadistic personalities tend to display recurrent aggression and cruel behavior. Sadism can also include the use of emotional cruelty, purposefully manipulating others through the use of fear, and a preoccupation with violence.

Theodore Millon claimed there were four subtypes of sadism, which he termed enforcing sadism, explosive sadism, spineless sadism, and tyrannical sadism"

There is renewed interest in studying sadism as a personality trait. Sadism joins with subclinical psychopathy, narcissism, and Machiavellianism to form the so-called "dark tetrad" of personality." "Alongside sadistic personality disorder is conduct disorder, not an adult disorder but one of childhood and adolescence. Studies have found other types of illnesses, such as alcoholism, to have a high rate of comorbidity with sadistic personality disorder"

Personality disorders are not easy to treat because usually the victim is the one who suffers, not the inflictor or aggressor. The inflictor uses projection and split as defence mechanisms. All of a sudden he (80% are men) becomes the victim and the victim becomes the inflictor. This is a difficult psychological problem with many confusing elements that leads to that the victim looses self-esteem and does not trust herself anymore.

In delinquent populations, SPD presents a comorbidity with antisocial personality disorder. SPD is also related to the diagnosis of sexual sadism in sexual murderers. It is associated with the diagnosis of psychopathy sexual serial killers but not in violent hospitalized offenders. Finally, the criminological and clinical interest of SPD prompts more research in this field.

(PDF) The sadistic personality disorder (researchgate.net)

@ Prof. S. Béatrice Marianne Ewalds-Kvist Thanks for your elucidation on the subject matter. Well appreciated!!!

Suraj Kapoor Thanks for your invaluable contribution. Best regards!!!

Could we say Sadistic Personality Disorder (SPD) is partly responsible for mass shooting, serial killing, serial raping, and terrorism being experienced in some developed nations of the world? This puzzling question is still begging for answers... Thanks!!!

Dear Seyi Festus Olatoyinbo . See the following useful links: https://jdc.jefferson.edu/cgi/viewcontent.cgi?article=1146&context=jeffjpsychiatry

https://psyarxiv.com/ur87t/download/?format=pdf

https://link.springer.com/content/pdf/10.1007%2F978-3-319-33228-4_808.pdf

https://www.medicinenet.com/can_sadistic_personality_be_cured/article.htm

Kindly see also the following useful RG links: Chapter Sadistic Personality Disorder

Article From Child Abuse to Developing Borderline Personality Disord...

https://www.emerald.com/insight/content/doi/10.1108/RAUSP-03-2019-0048/full/html

https://www.dovepress.com/borderline-avoidant-sadistic-personality-traits-and-emotion-dysregulat-peer-reviewed-fulltext-article-NDT

Also check please the following useful links: https://www.scirp.org/journal/paperinformation.aspx?paperid=103259

https://www.journalagent.com/phd/pdfs/PHD-36002-CASE_REPORT-TUNC%5BA%5D.pdf

https://www.science.gov/topicpages/s/sadistic+personality+disorder

https://www.mentalhelp.net/blogs/sadistic-personality-disorder-the-cleveland-tragedy/

@ Prof. Aref Wazwaz The useful links provided are heartily appreciated. My best regards always Sir.

You are most welcome dear

Prof. Seyi Festus Olatoyinbo

Wish you the best always.

Unfavorable experiences during childhood or in early stages of sexual development are believed to be one of the major contributing factors in the development of a sadistic personality. It has also been observed that sadism or a sadistic personality can also get developed in an individual through learning.

https://www.mentalhelp.net/blogs/sadistic-personality-disorder-the-cleveland-tragedy/

Most cases of sadistic behavior require counseling and therapy to modify a person's behavior. To completely cure sadistic personality, patients must undergo long-term treatment. The patient's compliance with the treatment is of utmost importance as non-cooperation to the therapy and counseling can hinder its success.

https://www.medicinenet.com/can_sadistic_personality_be_cured/article.htm

Also, kindly check:

https://www.psychologytoday.com/us/blog/the-integrationist/201408/dealing-everyday-sadists-and-other-dark-personalities

@ Dr. Manal Hadi Kanaan Your invaluable contributions and useful links provided are highly appreciated. My best regards always!!!