I was always told by my family members as a kid that I was an introverted child. I often kept to myself, preferring to play alone with my stuffed animals instead of with the other kids at daycare. I had trouble talking to other people, whether they were my age or adults, including my own family members. As I got older and decided to force myself out of my comfort zone to be more outgoing, I realized that I hadn't been isolating myself out of enjoyment, but rather out of anxiety and a need to protect myself against judgment from others. I didn't connect the dots until later when I took the infamous Myers-Briggs MBTI personality test. In this test, one of the criteria that is being tested is how introverted or extroverted someone’s personality is, as represented by a letter i or a letter e. The results that I received, to my surprise, showed that I had more extroverted tendencies than introverted ones. But how could this be? I began to read about the different personality types and found that introverted people actually preferred being alone, rather than isolating themselves because of a fear of social situations. That was the first time that I realized there was a difference between introversion and social anxiety. 

I wondered what being an introvert truly meant. Where does it come from? How does it differ from social anxiety? Is it something that can be grown out of, or is it something you are born with that is a part of you for the rest of your life? Is it a personality trait or a mental divergence? This thought process brought me to an overarching question: should introversion be classified as a mental disorder? At first, this sounds ridiculous - introversion is just a personality trait, not an illness. However, the word “disorder” can be misleading—many mental disorders are simply differences in brain chemistry and don't necessarily entail illness or malady. Because of this, introversion could be considered a mental disorder because of its similarities to some other disorders. However, this may not be beneficial due to the preexisting stigmas. It is crucial to appreciate that disorders are not necessarily a bad thing as they may initially seem in order to understand the stigma around psychopathology (which is a less harsh term for mental disorder and has nothing to do with psychopathy). For example, ADHD is considered psychopathology and, though it has its drawbacks and stigmas, is generally looked at as more of a personality type than a disorder. However, ADHD impacts less than 10% of the population, as do most other mental disorders, where 30-50% of the world's population is estimated to be introverted (McInnes). Could this mean that such a large portion of the population could have a disorder? Well, think about it; how many people can you name with a “normal” brain? A completely neuro-typical, basic prototype of a brain with no mental disorders or illnesses is less common than one might think. Even people who seem like they would have this standard brain may not, as a majority of people have at least one of what we would consider an abnormality in their brain. So is it unreasonable to think that we could group introversion into this category the same way we do with social anxiety, ADHD, and so many others? 

PERSONALITY VS DISORDER

Personality and psychopathology are often thought to be very different aspects of a person’s identity that can influence each other. Personality is usually studied under counseling psychology, while psychopathology is generally more studied under clinical psychology. Because of these different fields of study, there is not an ultimate defining factor between the two. According to the National Library of Medicine, a mental disorder is defined as:

A syndrome characterized by clinically significant disturbance in an individual's cognition, emotion regulation, or behavior that reflects a dysfunction in the psychological, biological, or development processes underlying mental functioning. Mental disorders are usually associated with significant distress or disability in social, occupational, or other important activities. (Stein et al.)

Mental disorders also do not include responses to stressors that are considered culturally acceptable, such as showing depressed behavior as a result of the loss of a loved one, which is situational and not persistent. A personality trait is described as a person’s pattern of attitudes, feelings, and behaviors that stay relatively consistent and can help predict motives; basically, why we do what we do. Personality and psychopathology are caused by both genetic and external factors, and the line between the two can at times be blurred. Many Axis I disorders (depression, generalized anxiety disorder, schizophrenia) could be considered stable personality structures because they often persist for someone's whole life (APA Dictionary of Psychology). For example, depression is classified as a mental illness, but some people feel depressed their entire lives and it impacts their mood, attitude, and behaviors. This could be seen as part of their personality rather than just a temporary condition. Conditions like generalized anxiety disorder or schizophrenia can also involve long-lasting personality traits. 

Additionally, some people struggle with personality behaviors or feelings like sudden anger or insecurity that don’t align with how they see their personality, which might be labeled as psychopathology. Extremes of some common personality traits, like high neuroticism (the trait disposition to experience negative effects like anger, anxiety, self‐consciousness, irritability, and emotional instability) or extreme introversion, can look very similar to mental health disorders (Widiger). For instance, very extreme introversion might resemble certain features of anxiety or even schizophrenia, while very low agreeableness or conscientiousness might align with personality disorders. However, these personality traits don't necessarily lead to symptoms directly, so it is arguable that they are not the same as psychopathology. This is where the majority of the confusion comes from, as “personality and psychopathology are sometimes merging into each other, sometimes related although conceptually and functionally different, and sometimes completely unrelated. A conclusion will be that this fact ought to have consequences for diagnostic classification” (Torgersen). The overlap between the two can make it hard to tell whether experiences related to mental illness, such as anxious or depressive behaviors and feelings, are a result of a disorder or responses to external factors, as stated in a research article by Pekka Jylhä: “the extent to which measures of the personality dimensions of neuroticism and introversion are influenced by symptoms of depression and anxiety or by episodes of depression, and whether neuroticism alone or both traits predispose one to depression remain unclear” (“Neuroticism, Introversion, and Major Depressive Disorder”). These blurred borders between classifications are important to consider when it comes to how we diagnose and classify mental health conditions, as well as personality traits, and why it is crucial to take this research deeper to understand the similarities and differences between each. 

DEFINING INTROVERSION

So, what does it mean to be an introvert? When you think of someone who is introverted, you probably think of a quiet, shy person who spends the majority of their time alone. While this stereotype is often relatively accurate, it does not encompass what introversion is in its entirety—the separation between introverted and extroverted people comes from how they respond to social stimulation. The main difference between the two, according to Mental Health America, is that “many introverts prefer minimally stimulating environments – they often like doing solo activities or spending time in familiar spaces or with people they know well. Being in busier or more active social environments isn’t necessarily anxiety-inducing for them – they just know it will take a lot more energy to be ‘on’” (“Introversion vs. Social Anxiety”). This is where the term “social battery” comes from. Extroverted people are stimulated by social interaction, making them feel energized and “recharged”, while introverted people are much more prone to overstimulation, which causes them to feel drained and less inclined to seek out stimulation (which is why they are often more comfortable in quieter, less busy environments) (“How to Tell if You’re an Introvert”). Introverts get their energy from within, meaning they need more alone time to recharge than others. Introversion also impacts self-concept, decreased impulsivity, and deeper creative thinking, which is why it is so prevalent when it comes to a person’s personality. 

While introverted and extroverted tendencies can change throughout someone's life, the root cause of each is due to genetics. The trait is heritable, and there are multiple genes thought to be associated with it. One of these genes is the D4DR gene, which is involved with dopamine reception and excitement levels; specifically when it comes to novelty-seeking and impulsivity, which are two of the main characteristics of extroversion. Introverts have shorter D4DR genes than extroverts, which makes them more sensitive to dopamine and less likely to engage in risky activities (“The Neuroscience Behind Introversion”). This gene is also associated with ADHD; specifically, having the “7-repeat” variant of the allele can make someone more susceptible to developing ADHD symptoms, which is what can cause impulsivity and risk-taking behaviors in people with ADHD the same way it does for people with extroverted personality (Ptacek). These similarities between the causes of introversion and causes of some symptoms of ADHD could explain the link between introverted personality and other mental disorders such as ADHD. 

Frequently associated with introversion is social anxiety, and the terms are often used interchangeably, though they are very different experiences. Social anxiety is rooted in fear and choosing to be alone out of self-protection, while introverts feel more comfortable alone in general and not due to anxiety. Another term that consistently gets grouped into the same category is social anhedonia, which is the lack of enjoyment from social situations and being around others (and has primarily been studied as a characteristic of schizotypy and schizophrenia). According to a research report done by Leslie H. Brown and colleagues, the separating factor between the three is the need to belong; “Social anxiety occurs when the need to belong is present but thwarted…. introversion is often characterized by the need to belong, whereas social anhedonia is characterized by disinterest in relationships and a lack of reward from social contact (low need to belong)” (Brown et al.). While introversion is considered a personality trait, both social anxiety and social anhedonia are considered psychopathology. However, there are overlaps between all three experiences when it comes to the desire to belong in society and how it conflicts with social discomfort. Each can cause different social behaviors and have their own set of possible negative side effects. 

THE GREY AREA

Grey matter is a type of tissue within the brain and spinal cord that processes information, controls memory, and enables conscious thought. Each individual naturally has different levels of grey matter in different parts of their brain, which can be impacted by age, gender, and genetic predisposition. However, more extreme differences in grey matter levels in different regions of the brain are related to psychopathology, as well as some aspects of personality (which does not mean that there is an overall larger or smaller amount of grey matter in the brain when it comes to mental disorders, but rather it is found that mental disorders correlate with varying levels in different regions of the brain). For example, it was found that “extraversion was negatively correlated with gray matter volume (GMV) of the bilateral amygdala, the bilateral parahippocampal gyrus, [and others]... [researchers] also found extraversion was positively correlated with GMV of the orbitofrontal cortex” (Zou et al.). These findings show that introverted brains do not necessarily have more or less grey matter than extroverted brains, but that there are different levels in different parts; specifically, introverts usually have higher densities of grey matter in the frontal lobe, which controls thinking and social skills, while extroverts have more in the medial orbitofrontal cortex, which monitors reward value and reward-related decision making. These differences in grey matter levels do not entail that one personality type is “smarter” or better in any way than the other, but just that different parts of their brains function at different levels, which relates to why introverted people tend to be deeper thinkers. 

People with social anxiety disorder also have differences in grey matter levels, particularly in regions such as the prefrontal cortex, which controls many things such as predicting the consequences of our own actions and the environment around us. A higher density of grey matter in the prefrontal cortex can contribute to this situational anxiety because it can induce heightened awareness of someone’s surroundings to the point that they can become hyper-aware of their surroundings, leading them to perceive many situations—especially social—as much more stimulating and intense than they are. This is where the greatest difference between introversion and social anxiety lies—in brains experiencing social anxiety, grey matter is denser in parts of the brain that are more focused on perceiving the external, while in introverted brains, grey matter differences occur more in the deeper-thinking parts of the brain. 

Additionally, an interesting pattern was found where there are larger differences in grey matter levels for people with personality traits that are considered to be in the grey area between personality and psychopathology (introversion, neuroticism, dark triad trait tendencies of narcissism, psychopathy, and Machiavellianism). A research experiment based on why depressed emotion is so often related to neuroticism found that “neuroticism [is] positively associated with the gray matter volume (GMV) in the dorsal medial prefrontal cortex (dmPFC). Mediation analysis was conducted to investigate the neural basis of the association between depressed emotion and neuroticism” (Yang et al.). With Machiavellian personality traits (high focus on self-interest using manipulation and deceit), there were found to be decreased volumes of grey matter in the dorsolateral prefrontal cortex (related to emotional regulation), and the orbitofrontal cortex, similar to introversion (Myznikov). These drastic differences in grey matter in certain regions of the brain associated with these more extreme types of personality could indicate that these traits should be considered as something more serious than personality traits, even if not necessarily mental disorders, but this “grey area” should be taken into account. 

MENTAL HEALTH IMPACTS OF INTROVERSION

Personality types have a considerable impact on our worldview, as well as the state of our mental health and how we deal with conflict. Introverts and extroverts have different ways of perceiving and dealing with certain experiences, which plays an important role when it comes to mental health. Overall findings show introverts are more susceptible to decreased mental well-being than extroverts, especially involving depression (Reid). Introverts are more likely to be compliant and have lower self-esteem than extroverts, and also have less social support than extroverts, which can make them more vulnerable to depression (Balder). This vulnerability is caused both by internal and external factors. Introverts’ deeper and more internal thinking can lead them to become more self-conscious and overthink. In a blog post on Introvert, Dear, Mary Wawrzonkowski describes a negative personal experience she has had when dealing with her introversion: the morning after a dinner party with her husband and their friends, she experiences what she calls the “introvert hangover”: “This morning, I’m still pretty exhausted. I can’t lie. My head is pounding and my body aches. My extroverted husband is laughing at me because I didn’t have a drop of alcohol last night…I’ve grown used to my “hangovers” and have accepted them as simply part of being an introvert” (Wawrzonkowski). Along with side-effect mental health issues like anxiety, introversion has negative symptoms of its own. This could change the way that we think about introversion, as it can directly cause negative effects and can be debilitating for some people, which is not a common effect of most personality traits. 

There are aspects of introversion that are harmless parts of someone’s personality, such as deeper, more creative thinking, enjoying time alone, and preferring to stay quiet and think internally rather than communicating all of their thoughts and feelings. However, there are parts of introversion that could also be considered as leaning towards a personality disorder, such as a greater susceptibility to experience anxiety and depression, as well as becoming irritable and physically uncomfortable with too much social interaction, which can be considered an abnormal and negative response to social stimulation. 

There are also stigmas around introversion due to many cultures and societies giving preference to extroverted personalities, with qualities like outgoingness and high activity levels being valued above introverted tendencies of reflection and solitude. This causes introverted people to be perceived as unsociable, less intelligent, and less capable than extroverts because of societal preference, which additionally can have a negative impact on mental health by causing introverted individuals to feel pressured to change their personalities. 

It took me many years to realize that I truly was an extrovert who was just inhibited by social anxiety, rather than an introvert as I had always thought. My personal experience of misinterpreting my own behavior highlights the misunderstandings that society as a whole has about introversion, often by using the term interchangeably with anxiety, though it is clear that the two are very different phenomena within the brain. Overall, introversion technically could be considered as an aspect of psychopathology due to the undefined grey area between personality characteristics and mental disorders. Introversion shares some traits with certain psychopathological conditions, such as an increased likelihood of experiencing anxiety or depression; however, that does not necessarily mean that it is enough for it to be considered a disorder in itself. The distinction between personality and mental illness is still too unclear, as traits like neuroticism, extreme introversion, Machiavellianism, and others can overlap with clinically diagnosed conditions. However, the question of whether it should be classified as a mental disorder is not just a matter of science, but one of perception and societal impact. Labeling introversion as a disorder could potentially do more harm than good; it could reinforce negative stigmas about mental health and perpetuate the idea that introverts need to be “fixed,” rather than simply understood. This is not just a question of whether or not introversion could be considered a mental disorder, but also a question of whether or not it should. 

Our current understanding of personality and mental illness is not yet deep enough to make classifications like this, so it is necessary to research personality and psychopathology more deeply, as well as the “grey area” in between in order to understand the boundaries between each. It would be beneficial for research involving personality and psychopathology to be studied together, rather than separately as they have been in the past. By understanding how the two work together, it will be possible to see the minute differences between each sphere, which gives more of a basis to compare what exactly makes the two similar and different. Using only our current understanding, classifying introversion as a mental disorder could lead to unnecessary medicalization of a natural, generally harmless personality trait. The majority of introverts do not experience extreme enough negative symptoms for there to be a need to get serious help or to feel that they need to change. Rather than attempting to pathologize introversion, we should work toward appreciating its unique strengths, such as deep thinking, creativity, and self-awareness. Just as I learned to separate my anxiety from my introverted tendencies, society must also differentiate between introversion and mental illness rather than assume all quiet, introspective individuals are struggling with something that needs to be fixed. 

In the future, as we learn more about the causes and structures behind these concepts, our understanding of personality and mental illness will become much clearer and more nuanced. Until then, our knowledge is based on assumptions and incomplete research of the complexity between personality and psychopathology that will one day become understood much more deeply. The end goal should not be to label introversion as a disorder, but to recognize and understand the diverse ways people experience and interact with the world.

​‌‌‍‍​‍APA Dictionary of Psychology. dictionary.apa.org/personality-trait.

​‌‌‍‍​‍Balder, Elizabeth A. “Introversion : Relationship With Mental Well-being.” UNI ScholarWorks, scholarworks.uni.edu/grp/301.

​‌‌‍‍​‍“How to Tell if You’re an Introvert.” WebMD, www.webmd.com/balance/introvert-personality-overview.

​‌‌‍‍​‍“Introversion vs. Social Anxiety.” Mental Health America, mhanational.org/introversion-vs-social-anxiety.

​‌‌‍‍​‍Jylhä, Pekka, et al. “Neuroticism, Introversion, and Major Depressive Disorder-traits, States, or Scars?” Depression and Anxiety, vol. 26, no. 4, Mar. 2009, pp. 325–34. https://doi.org/10.1002/da.20385.

​‌‌‍‍​‍Lai, Han, et al. “Brain Gray Matter Correlates of Extraversion: A Systematic Review and Meta‐analysis of Voxel‐based Morphometry Studies.” Human Brain Mapping, vol. 40, no. 14, June 2019, pp. 4038–57. https://doi.org/10.1002/hbm.24684.

​‌‌‍‍​‍Myznikov, Artem, et al. “Dark Triad Personality Traits Are Associated With Decreased Grey Matter Volumes in ‘Social Brain’ Structures.” Frontiers in Psychology, vol. 14, Jan. 2024, https://doi.org/10.3389/fpsyg.2023.1326946.

​‌‌‍‍​‍Ptacek, Radek, et al. “Dopamine D4 Receptor Gene DRD4 and Its Association With Psychiatric Disorders.” Medical Science Monitor, vol. 17, no. 9, Jan. 2011, pp. RA215–20. https://doi.org/10.12659/msm.881925.

​‌‌‍‍​‍Reid, Sheldon. “Personality Types, Personality Traits, and Mental Health.” HelpGuide.org, 9 Sept. 2024, www.helpguide.org/mental-health/psychology/personality-types-traits-and-how-it-affects-mental-health.

​‌‌‍‍​‍Results - OpenURL Connection - EBSCO. research.ebsco.com/linkprocessor/plink?id=e2af8b87-8ac2-335e-9c2d-581fefb988bc.

​‌‌‍‍​‍Stein, Dan J., et al. “What Is a Mental Disorder? An Exemplar-focused Approach.” Psychological Medicine, vol. 51, no. 6, Apr. 2021, pp. 894–901. https://doi.org/10.1017/s0033291721001185.

​‌‌‍‍​‍Torgersen, Svenn. “Personality May Be Psychopathology, and Vice Versa.” World Psychiatry, vol. 10, no. 2, June 2011, pp. 112–13. https://doi.org/10.1002/j.2051-5545.2011.tb00030.x.

​‌‌‍‍​‍Wawrzonkowski, Mary. “The Introvert Hangover Is Awful.” IntrovertDear.com, 25 June 2021, introvertdear.com/news/the-introvert-hangover-is-awful.

​‌‌‍‍​‍Widiger, Thomas A., and Joshua R. Oltmanns. “Neuroticism Is a Fundamental Domain of Personality With Enormous Public Health Implications.” World Psychiatry, vol. 16, no. 2, May 2017, pp. 144–45. https://doi.org/10.1002/wps.20411.

​‌‌‍‍​‍Yang, Junyi, et al. “Regional Gray Matter Volume Mediates the Relationship Between Neuroticism and Depressed Emotion.” Frontiers in Psychology, vol. 13, Oct. 2022, https://doi.org/10.3389/fpsyg.2022.993694.

​‌‌‍‍​‍Zou, Liwei, et al. “Relationship Between Extraversion Personality and Gray Matter Volume and Functional Connectivity Density in Healthy Young Adults: An fMRI Study.” Psychiatry Research Neuroimaging, vol. 281, Sept. 2018, pp. 19–23. https://doi.org/10.1016/j.pscychresns.2018.08.018.