Mental Illness vs. Personality Disorder

Katelyn Hagerty

Reviewed by Katelyn Hagerty, FNP

Written by Geoffrey Whittaker

Updated 01/11/2023

Mental illness affects a staggering portion of the world’s population — as many as one in five people experience a form of it each year. Unsure whether your condition qualifies as a mental illness? It might help to understand the difference between mental illness versus personality disorder.

Terminology in the mental health community is rarely (if ever) simple because things often change. Manic depression, for instance, is now called bipolar disorder, and bipolar disorder actually has two subcategories.

These are among just the latest modifications to an ever-evolving field of medicine that used to consider bloodletting an appropriate treatment for releasing evil spirits possessing the body. 

We digress. Whether you have a personality disorder or are wondering if your diagnosed mental illness is actually a personality disorder, what you’re ultimately trying to do is learn more about your condition (or someone else’s) based on how each is classified. 

We’ll walk you through this oft-confusing subject of mental illness versus personality disorder. Let’s start with the basics.

According to the National Library of Medicine, a personality disorder is characterized by a long and often grueling experience of thought patterns and behaviors that are both unhealthy and inflexible.

Many might say being a Nickelback fan fits this definition, so it’s important to go a little deeper and look at the symptoms.

A person with a personality disorder may experience the following as part of their condition:

  • Antisocial behavior

  • Poor social function

  • Distorted views of reality

  • Maladaptive behavior

  • Narcissism

  • Paranoia

People with personality disorders tend to struggle to connect with others and function in normal social relationships, social situations or professional roles. Though the symptoms may ebb and flow over time, they often make it difficult for a person to properly integrate or function normally — or to maintain stable relationships, in general.

There are several common types of personality disorders: 

  • Borderline personality disorder

  • Narcissistic personality disorder

  • Schizoid personality disorder

  • Schizotypal personality disorder

  • Delusional disorders

  • Histrionic personality disorder

  • Paranoid personality disorder

  • Antisocial personality disorder

  • Dependent personality disorder 

  • Avoidant personality disorders

  • Obsessive-compulsive disorder (OCD)

Learn more about mental illness versus personality disorder below.

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According to the National Institute of Mental Health (NIMH), a mental illness is any disorder that affects cognitive, behavioral or emotional function in a way that causes impairment, dysfunction or distress.

In the clearest terms, any type of personality disorder meets the textbook criteria for mental illnesses. Many things fit this definition, including depressive disorders, anxiety disorders and post-traumatic stress disorder (PTSD).

If you remember back to your high school geometry classes, all squares are rectangles, but not all rectangles are squares. That means a square is always a rectangle, but a rectangle isn’t always a square.

In this case, we can essentially replace “square” with “personality disorder” and “rectangle” with “mental illness.” Any time someone is diagnosed with a personality disorder, they’ve already met the qualifications to have a mental illness.

Mental Health Disorder Severity

But here’s where things can get tricky. The NIMH categorizes mental illnesses into two categories: any mental illness and serious mental illness. Any mental illness is typically a milder condition. Low-to-moderate levels of depression or anxiety meet these qualifications. 

Serious mental illness, meanwhile, causes such a burden that it limits major life activities. You may not be able to work, maintain personal relationships or take care of yourself.

While depression and anxiety can meet these requirements if they’re severe enough, personality disorders tend to be more difficult to pin down — especially since the people who have them are often reluctant and avoidant of help.

In other words, it can sometimes be hard to determine the seriousness of someone’s personality disorder because they may not seek effective treatment.

Of course, if a personality disorder becomes severe enough to warrant intervention, you can assume it’s serious. After all, this would indicate it’s harming normal day-to-day functions.

But it’s possible for a person with severe personality disorder to function or cope enough to function at the bare minimum while disguising their illness.

There are two ways to look at the question of whether you can have both a personality disorder and a mental illness. Let’s look at the simplest one first. 

Since a personality disorder is already a mental disorder, you technically always have a mental illness when you have a personality disorder. So if you have OCD or schizophrenia, you have a mental illness.

But the more complicated (and potentially more important) way of looking at it is to ask whether you can have a personality disorder and another mental illness, like anxiety or depression. And the answer is an emphatic yes.

Research shows a high comorbidity between conditions like borderline personality disorder and mood disorders like depression.

Personality disorders can be extremely difficult to treat. It depends on the “cluster” of personality disorders a person belongs to: A, B or C.

Cluster A Personality Disorders

Cluster A disorders include paranoia, schizoid, and schizotypal schizophrenia. Patients in this category who are suspicious or paranoid will often avoid things like group therapy — or therapy in general — out of a lack of trust in the practice and the people involved. If unwilling, they may simply be impossible to treat.

Cluster B Personality Disorders

Cluster B patients, on the other hand, can benefit from both group therapy and individual therapy. Antisocial, histrionic, borderline and narcissistic personality disorders can benefit greatly from this introspection.

Cluster C Personality Disorders

Lastly, the avoidant, dependent, and obsessive-compulsive personality types in Cluster C can benefit from treatment options like selective serotonin reuptake inhibitors (SSRIs) and cognitive behavioral therapy (CBT).

Any treatment plan, however, should be carried out with the oversight of a mental health professional, regardless of what the personality disorder sufferer is diagnosed with. And that leads us to our final point.

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psychiatrist-backed care, all from your couch

We’re assuming you made your way to this article to clear up some lingering questions after speaking with a healthcare professional — but that’s not always the case. You may be struggling right now while seeking answers from home concerning signs you’ve seen in your behavior or that of someone you love. 

If you’re currently exploring this solo, it’s time to get help.

There are many ways to seek help and support. Existing primary care doctors and counselors, religious and community organizations and even educational resources through a school or university can help support you or someone else.

But it all starts with reaching out for help — nobody’s going to drop solutions in your lap.

If you’re not sure where to begin, let us help you figure things out. Our mental health resources can answer more questions if you have them. And our online therapy platform can connect you with mental health providers 24/7, from the convenience and safety of wherever you are (as long as you have WiFi).

Personality disorders don’t have to define you, and neither do mental illnesses. But until you seek help, they’re going to have more control over your life than you’d ever give them willingly. 

Take back that control today.

3 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. U.S. National Library of Medicine. (n.d.). Personality disorders. MedlinePlus. Retrieved December 5, 2022, from
  2. Fariba KA, Gupta V, Kass E. Personality Disorder. [Updated 2022 Apr 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:
  3. U.S. Department of Health and Human Services. (n.d.). Mental illness. National Institute of Mental Health. Retrieved December 6, 2022, from

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Katelyn Hagerty, FNP

Kate Hagerty is a board-certified Family Nurse Practitioner with over a decade of healthcare experience. She has worked in critical care, community health, and as a retail health provider.

She received her undergraduate degree in nursing from the University of Delaware and her master's degree from Thomas Jefferson University. You can find Katelyn on Doximity for more information.

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