Mental Illnesses Among Some of America’s Most Infamous Serial Killers

Psychologists have spent decades studying the brains of known serial killers in an attempt to understand what makes them become such vicious killers. While mental illnesses were found in some of America’s most loathsome killers, it’s important to note that most people suffering from these illnesses do not commit any violent offenses.



Schizophrenia is a severe mental disorder that affects how a person thinks, feels and behaves. Symptoms range from hallucinations and delusions to emotional flatness and catatonia. It is one of the most common mental disorder diagnosed among criminals, especially serial killers.
  • David Berkowitz: “Son of Sam” killed six people during the 1970s. After he was caught, he claimed that his neighbor’s dog told him to do it. He was later diagnosed with paranoid schizophrenia.
  • David Gonzalez: killed four people in 2009 and claimed he was inspired by Nightmare on Elm Street. Gonzalez had previously been diagnosed with paranoid schizophrenia but wasn’t properly treated.
  • Ed Gein: the inspiration for fiction’s Norman Bates, Buffalo Bill and Leatherface. Interestingly enough, after being diagnosed with schizophrenia and pronounced insane, he was a ‘model patient’ while sentenced to life imprisonment in psychiatric institutions.
  • James Eagan Holmes: Mass murderer currently serving 12 life sentences plus 3,318 years without parole. Holmes was diagnosed with schizophrenia by 20 doctors after killing 12 people and injuring 70 in a Century 16 movie theater in 2012.
  • Jared Lee Loughner: the mass killer who gunned down Representative Gabby Giffords and 18 others outside a Tucson-area supermarket in 2011. Loughner apparently wrote a chilling poem, that included a reference to the slaying of Present John F. Kennedy, for the event and left copies at the crime scene. After his arrest, two medical evaluations diagnosed him with paranoid schizophrenia.
  • Richard Chase: “the vampire of Sacramento” killed six people in California and drank their blood. Before his murder spree began in 1977, he was involuntarily committed to a mental institution after being taken to a hospital for injecting rabbit’s blood into his veins. He was discharged the year prior, after undergoing treatment for paranoid schizophrenia and being deemed as ‘no longer a danger to society’.


Characterized by impulsive behaviors, intense mood swings, feelings of low self-worth and problems in interpersonal relationships, borderline personality disorder seems more common among female criminals.
  • Aileen Wuornos: the woman who inspired the 2003 film “Monster” starring Charlize Theron, confessed to seven murders in Florida. Afterward, she was diagnosed with borderline personality by the state’s expert psychologist.
  • Jeffrey Dahmer: the “Milwaukee Cannibal” was diagnosed with borderline personality disorder after standing trial for seventeen murders. He was found guilty and sentenced to life in prison. However, Dahmer was murdered two years later by a fellow inmate who alleged that he was disturbed not only by Dahmer’s crimes but by a habit Dahmer developed of fashioning severed limbs from prison food to antagonize other inmates.
  • Kristen H. Gilbert: killed four patients at the Northampton VA hospital, where she worked at, in order to gain the attention of a VA police officer she was having an affair with. Before the murders, she had been a patient at psychiatric hospitals in the area and was eventually diagnosed with borderline personality disorder.


Known in the past as “psychopathy,” this mental disorder is characterized by a total lack of remorse and disregard of the feelings of others. People with APD may lie, act out violently, or break the law. While it’s reported that APD only affects 0.6% of the population, it may affect up to 47% of male inmates and 21% of female inmates. It’s also been diagnosed among three of the most ruthless serial killers.
  • Charles Manson: leader of the “Manson Family” was diagnosed with antisocial personality disorder after showing signs of the condition throughout his life. The first documented instance of this occurred when Manson was in first grade. He would recruit gullible classmates, mostly girls, to attack the students he didn’t like. Afterward, he’d swear to teachers that his kid followers were just doing what they wanted.
  • John Wayne Gacy: the “Killer Clown” raped and killed 33 boys and young men. Unremorseful until the end, Gacy’s final words before being executed by lethal injection on May 10, 1994, were “Kiss my ass.”
  • Ted Bundy: an infamous killer and necrophile, who confessed to 30 murders in the 1970s, although he told his lawyer the number was closer to 100. Recently, a group of 73 psychologists got together with the University of Kentucky and agreed that Bundy had antisocial personality disorder. In fact, 80% of the team believe Bundy to be the perfect example of the disorder.



  • Bonn PhD, Scott. John Wayne Gacy: The Diabolical “Killer Clown”. Psychology Today. 2014.
  • Gainsburg, Marissa. So, Exactly Which Mental Health Disorder Did Bundy Have, Anyway? Women’s Health. 2019.
  • Glowatz, Elana. Was Charles Manson a Psychopath or Sociopath? Sharon Tate’s Murderer’s Mysterious Pathology. Medical Daily. 2017.
  • com Editors. Jeffery Dahmer Biography. 2014, updated 2019.
  • Ranker Crime. 9 Serial Killers Who Suffered from Mental Illness. Ranker.com.
  • Forensic Colleges. Dangerous Minds: The Mental Illnesses of Infamous Criminals.


Since completing my undergraduate studies, I've dedicated my time to supporting and empowering individuals with behavioral health issues. This blog is to be a platform for the behavioral health community; examining the history of behavioral health and the progressions made within the field while providing information and resources to those who need it.

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