Sensitive people.., may have suffered much pain (they were often of a delicate constitution), but the damage to their inner selves was less. They were able to retreat . . to a life of inner riches and spiritual freedom (i). Only in this way can one explain the apparent paradox that some prisoners of a less hardy make-up often seemed to survive camp life better than did those of a more robust nature. [V. Frankl]
From the therapists I have experienced, they do not take into account personality styles when practicing their trade. I recall being given a list of cognitive distortions, e.g., “all-or-nothing thinking” or “filtering”, only to come up with the conclusion that therapists are interfering with types of reasoning that we apply in social circumstances that may have unintended consequences. So I don’t wholeheartedly accept them. If we think the evidence for CBT is uncontroversial, then this means that we haven’t researched it (iv).
The fact that I had a difficult time accepting and using CBT shows that this is a personality quirk, but it was interpreted instead as being adversarial and not open-minded. This post will review how some, namely those with sensory-processing sensitivity—the essence of introversion (iii)—must process things deeply and thoroughly before accepting. We all have a natural inclination to learn and understand how to navigate our outer worlds, but we do this in our own way and may not benefit from the “fix” of a therapist (v).
The What It Is
I did a post titled “The What It Is” that claimed that we can get to the essence of a trait if we observe a physiological phenomenon upon stimulation. This is as close as we can get to a trait’s essence, but it is not a Platonic reality or something that exists beyond perception. Jerome Kagan has identified the essence of the introversion trait as being inhibitedness (iii) which was a label given to describe what happens with twenty percent of infants—always in this proportion—upon stimulating them with say a bright light.
Inhibited infants show EEG activation on the right frontal area under resting conditions while most infants show activation in the left frontal area. The right frontal area in the brain is where negative “affect” or emotion occurs. 
Studies show that infants that are inhibited are likely to develop the personality traits of introversion and neuroticism or demonstrate the behavioral disposition of shyness. Shyness is when we feel inhibited or fearful around others and become extremely self-conscious. We can be introverted and shy or introverted and not shy. Currently, introversion is studied as a function of sociability (see reader’s comment below), and introverts prefer select and few social interactions as they can become easily overwhelmed. But once we focus on sociability in terms of energy expenditure, although still correct, it misses the more fundamental roots of the trait.
Jung was right to describe innate introversion not in terms of sociability but as a preference to process information from the external world in a thoroughly subjective way. 
There is reason to believe that this trait of inhibitedness is a misnomer and should be labeled sensory-processing sensitivity or HSP (Highly Sensitive Person). Dr. Aaron has framed this inhibitedness in terms of the central nervous system’s sensitivity which requires it to take life in small pieces for deep processing. But thirty percent of HSPs are extroverts. Research, however, shows that this subset of HSPs may have developed into introverts if they did not have positive and accepting social experiences.
HSP is characterized by “a tendency to ‘pause to check’ in novel situations, greater sensitivity to subtle stimuli, and the engagement of deeper cognitive processing strategies for employing coping actions, all of which is driven by heightened emotional reactivity, both positive and negative. [4.1]
Introverts are more sensitive to stimuli and stimulants, more vigilant during discrimination tasks, more influenced by implicit learning paradigms, more reflective when given feedback, and slower to acquire and forget information due to their depth of processing input into memory. 
So by getting closer to the biology of the trait, known as temperament, we can see that it is sensitivity that makes introverts more easily overwhelmed. Think for a moment about how being “more easily overwhelmed” will affect how we approach life. This means that we will have rehearsed questions before answering because we feel shame more deeply, that people may exhaust us instead of energize us, but it is all rooted in protection from feeling overwhelmed, which is why sensitivity is the essence of the trait (ii, iii).
This greater sensitivity and its physiological correlates are found at all levels of the nervous system, from measures of skin conductance, reaction times, and evoked potential, to subcortical areas of the brain, to differences in cortical processing (generally more right hemi- sphere activity. 
This sensitivity can explain introverts’ lower sociability (iii), which is to avoid feeling overwhelmed due to their exaggerated response to stimuli, but I haven’t seen an adequate explanation of how responsiveness contributes to deeper processing of information despite being intuitive. But there are differences between how introverts and extroverts process information, where introverts tend to be more reflective, thorough, and profound, extroverts are not. In terms of IQ, introversion does not, however, confer an advantage.
Introverts rely much more on acetylcholine-mediated pathways [my insert: extroverts favor dopaminergic pathways], resulting in a longer circuit through the frontal lobes of the brain, a longer time in the planning and decision-making mode, and slower memory retrieval. They have greater synthesis of information from different parts of the brain too. 
i) Spiritual doesn’t have to be divine because it is also transcendence of the here and now to create meaning and purpose. Inner riches means the rich life of our inner thoughts and feelings that we can console and rely on. For me, when I learn something that integrates nicely into my larger understanding of things, then I feel satisfaction. The things that I learn are personally meaningful.
ii) This discussion is relying on a categorization of introverts versus extroverts, but we can’t explain the individual in such stark ways since traits are on a continuum and combine in complex ways with other traits. The larger point, however, is that people vary in how they interact with their outer worlds.
iii) This may not be the true trait that underlies introversion because of confounding variables. The fact that we aren’t very social (introversion), for example, may not be because we are easily overwhelmed (sensitive) but instead due to aversive social experiences. So the trait of sensory-processing sensitivity is a subset of all introverts. Psychologists are still trying to discern the different behaviors that make up a trait, and they certainly are not monolithic. They then squeeze them into a nice and tidy category.
…Well, whatever we name this trait, the most recent research suggests that the general strategy of being more sensitive is determined by multiple genes, and these do not come with names on them. We scientists are creating the names—introverted, inhibited, shy, sensitive, and responsive. As we learn more, we will become more accurate. For now, if you are socially extroverted yet feel things deeply, ponder the meaning of life, reflect before acting, and need a lot of down time, please, be patient. If you are socially introverted but not especially bothered by loud noise, are not very emotional, and make decisions rather easily, please also be patient. We’ll get it right about you, too…[Elaine Aaron]
iv) The status quo is that there is empirical support from CBT, but it depends on which meta analysis we accept. In my view, CBT probably does work to alleviate “dysfunctional” thoughts and feelings that may contribute to depression and anxiety. But these dysfunctional thoughts may have a purpose that if we eliminate them, then we may not get to the source of what is causing the depression and anxiety. I have touched upon this before on items twelve and thirteen of this post. I am not alone on this concern.
As far as unintended consequences, if we are familiar with the cognitive distortions, then we will see that it is essentially pointing out that we have cognitive biases such as the confirmation bias, which is labeled as “filtering”. But this is how the brain naturally works to find evidence for something. It is simply saying that we should look for other causes before making a hasty conclusion. This is usually a good thing. My concern, however, is that this prevents us from using our intuition when it comes to assessing people.
v). This isn’t fair to therapists because it reflects my experiences with a small sample of them. Therapy is an opportunity to raise our emotional IQ and to learn about ourselves. They can be an invaluable coach to us as we navigate the rough terrains of our lives.
 Aaron, Elaine. Revisiting Jung’s Concepts of Innate Sensitiveness. Journal of Analytical Psychology.
 Aaron, Elaine. Sensory Processing Sensitivity and Its Relation to Introversion and Emotionality. Journal of Personality and Social Psychology.
 Aaron, Elaine. The Clinical Implications of Jung’s Concept of Sensitiveness. Journal of Jungian Theory and Practice.
 Aaron, Elaine. Sensory Processing Sensitivity in the context of Environmental Sensitivity. Neuroscience and Behavioral Reviews.
[4.1] Booth, Charlotte; Standage, Helen; Fox, Elaine (1 Dec 2015), “Sensory-processing sensitivity moderates the association between childhood experiences and adult life satisfaction
 Olsen, Marti. The Introvert Advantage: Making the Most of Your Inner Strengths
 Schmidt, Louis. Extreme Fear, Shyness, and Social Phobia (Series in Affective Science)