Therapeutic interventions like psychotherapy don't just teach people to function better with their existing traits. Meta-analyses show these treatments lead to fundamental changes in personality, with the most significant effect being a reduction in neuroticism.
Data shows personality traits exist on a smooth continuum. While algorithms can force people into categorical "types" (like Myers-Briggs), these groupings are not stable or replicable across different samples, meaning there are no natural, distinct personality categories.
Psychology is moving away from a firm distinction between personality and mental health. A persistent mental health issue, by definition, is a stable pattern of experience and behavior, which fits the scientific definition of a personality trait. The two concepts are fundamentally intertwined.
Contrary to the idea that introverts simply find pleasure in solitude, research shows that extroverts experience more positive emotion than introverts even when they are by themselves. This suggests extroversion is tied to a more fundamental sensitivity to reward in the brain, not just sociability.
The Hierarchical Taxonomy of Psychopathology (HITOP) model reveals that symptoms of mental health problems cluster into five major dimensions that closely correspond to the Big Five personality traits. This suggests mental illness can be understood as an extreme expression of normal personality variation.
Individuals high in neuroticism don't just perceive situations as more stressful; data suggests they are more likely to end up in objectively stressful, challenging, or traumatic situations later in life. This indicates the personality trait may itself contribute to the creation of a difficult environment.
While the Big Five model is robust, it doesn't replicate in all languages when derived from local dictionaries. The most cross-culturally stable structure is a two-factor model consisting of "Dynamism" (extroversion, competence) and "Social Propriety" (dependability, reliability).
Personality stability isn't just one concept. 'Rank order' stability measures if the most extraverted person in a group remains the most extraverted over time. 'Mean level' stability tracks how the average trait level for an entire population changes with age, such as dips in conscientiousness during adolescence.
Instead of a categorical disease model (virus present/absent), mental health should adopt a dimensional approach like internal medicine. Just as blood pressure exists on a spectrum, psychological traits do too. Treatment decisions can be based on evidence-backed cutoffs for risk, eliminating the need for arbitrary diagnostic boxes.
While major life events can alter personality, most do so unpredictably. Across large populations, only two events have been found to reliably predict personality shifts: getting a first job and entering a first serious romantic relationship. Both tend to increase conscientiousness and agreeableness.
At the Big Five level, gender differences in personality appear small. However, breaking down the traits into sub-facets reveals more pervasive differences. For example, within Extraversion, men score higher on Assertiveness while women score higher on Enthusiasm, effects that cancel each other out at the broader level.