Now that we have a better understanding of what is meant by "personality," let's return to the original question. What is a personality disorder? Many psychologists and mental health professionals have struggled with how to define a "disordered" personality, as distinguished from a healthy one. For our purposes, it may be most helpful to think about someone with a healthy personality as a person who accurately interprets their environment. Thus, their subsequent thoughts, feelings, and behaviors reasonably correspond to the reality of their environment. As a result, they can accurately appraise their own strengths, weaknesses, and motivations. Likewise, they can accurately identify the strengths, weaknesses, and motivations of others. Therefore, a person with a healthy personality is someone who can navigate the world effectively, with a minimum of unproductive detours, and who usually manages to steer clear of major storms.
If we were sailors navigating the world on the open seas, we would need to have a set of precisely tuned, highly sophisticated instruments in order to navigate effectively. Our navigational tools would need to be capable of swiftly adjusting to changing conditions (weather conditions, cargo weight, etc.). The same is true of our personalities. In other words, we must be able to adjust our reactions to the specific circumstances of each situation. This means our perceptions and interpretations of the world must not only be accurate, but also nuanced. This requires of our personalities a high degree of flexibility in order to take into account the special needs and circumstances of every unique situation we encounter. Each situation may need to be interpreted differently. Our reactions must be finely tuned and properly adjusted to precisely correspond with the unique demands of each individual situation. Unfortunately, people with personality disorders lack this essential flexibility, and respond to situations and events with a characteristically rigid constellation of thoughts, feelings, and behaviors. This inflexibility, and difficulty forming nuanced responses, represents the primary difference between healthy and disordered personalities.
The question remains, how do we account for this fundamental difference between healthy and unhealthy personalities? The answer seems to lie in the "navigational instruments." It appears that people with personality disorders are missing an important tool. Research by Fonagy and his colleagues (1996) found that people with personality disorders seem to lack a highly necessary skill called "mentalization." Mentalization refers to the ability to reflect upon the behaviors, internal states, and motivations of both ourselves and other people. The ability to mentalize may enable people with healthy personalities to adjust their behaviors to the differing demands of each unique situation. In other words, what permits this flexibility may be the capacity to reflect upon one's own behaviors and motivations, and to reflect upon the behaviors and motivations of others. Thus, the ability to mentalize permits an accurate assessment of each unique situation that renders an appropriate response for that situation.
This concept of flexibility further suggests that what may be a healthy and adaptive response in one circumstance or situation, might be maladaptive in another. Typically, healthy personalities are flexible enough to account for these differences and respond accordingly. Let's use an example to illustrate this concept. Suppose I work as a receptionist within a prison. It is healthy and advantageous for me to adopt a vigilant approach in this kind of workplace. Thus, it is adaptive for me to be cautious and somewhat suspicious of others because these thoughts, feelings, and behaviors properly match that particular situation and circumstance. Now, imagine what might happen if I attempted to use this same approach in a different workplace setting; say for example, a clothing store. If I am constantly vigilant and distrustful of others, and suspect my co-workers or customers might try to harm me at any moment, I will likely behave in a manner that is overly-guarded, hostile, suspicious, or withholding. This approach would certainly interfere with my performance at the clothing store, and would negatively affect my interactions with co-workers, supervisors, and customers.
This example illustrates what can happen when people attempt to navigate the world with a rigid, inflexible approach. People with healthy personalities would account for the differing demands of each workplace, and would select behaviors appropriate to each one. This flexible approach increases the likelihood they will experience workplace satisfaction and success. In contrast, people with personality disorders, who cannot so easily adjust their approach, will eventually experience dissatisfaction and a lack of success.
While we may intuitively recognize that it is not sensible to use the same approach for every situation, it doesn't answer, why is this considered adaptive and healthy? The flexibility that is characteristic of people with healthy personalities is considered "adaptive" because their patterns of thoughts, feelings, and behaviors do not usually lead to any significant distress, and ensure a reasonable degree of success and satisfaction. Or, to continue with our metaphor, they navigate their world with few unproductive detours and typically steer clear of major storms. Conversely, the inflexibility that is characteristic of "disordered" personalities is considered maladaptive because it leads to distress, dissatisfaction, and failure. These unfortunate folks frequently experience stormy relationships and repeatedly find themselves in situations that lead to their unhappiness and lack of success. When personality traits consistently cause distress and impair interpersonal relationships, or impair one's ability to function successfully at work, we then begin to consider the possibility of a personality disorder.
Of course, we all have our issues, conflicts, and hardships that certainly can cause us distress. We don't behave well all the time. Sometimes we annoy other people. In other words, some storms are inevitable and some detours are difficult to resist. As we mentioned earlier, a personality disorder is a variant form of a normal, healthy personality. Therefore, it is quite reasonable to expect that healthy personalities will experience some difficulty some of the time. In order for a personality disorder to be diagnosed, an enduring pattern needs to be present. This pattern consists of problematic behaviors and traits, starting early in life, observed across many different situations, over a long period of time, that cause significant distress.