Can Personality Change? What Longitudinal Research Shows

The popular belief that personality is "set by 30" is wrong. Decades of longitudinal data show that personality continues to change throughout adulthood, and that deliberate change is possible.

The Old View: Personality as Fixed

For much of the 20th century, personality was treated as essentially stable after early adulthood. William James wrote in 1890 that character is "set like plaster" by age 30. This view persisted in popular culture and even in parts of the research community well into the 2000s.

The intuition behind it isn't crazy. People do tend to become more like themselves over time. Your personality at 30 correlates with your personality at 40 more strongly than your personality at 10 correlates with your personality at 20. There is genuine stability.

But stability is not the same as immutability. A correlation of r = 0.70 between personality at age 30 and age 40 (a typical finding) means substantial consistency, but it also means roughly half the variance is unexplained. People change.

What the Longitudinal Data Actually Shows

The most comprehensive evidence comes from Roberts, Walton, and Viechtbauer's (2006) meta-analysis of 92 longitudinal studies covering personality change from age 10 to age 70+. Their findings:

Conscientiousness increases throughout adulthood. The biggest gains occur between ages 20 and 40, but the trait continues to rise into old age. People become more organized, responsible, and self-disciplined as they age. The effect size is substantial: approximately 1 standard deviation of change from age 20 to 65.

Agreeableness increases, mostly after age 30. People become more cooperative, trusting, and accommodating. The change is moderate but consistent across studies and cultures.

Neuroticism decreases, especially in young adulthood. Emotional reactivity and negative affect decline from the late teens through the 40s. Women show a steeper decline than men. This is one of the most consistent findings in the personality change literature.

Openness shows a complex pattern. It increases slightly in adolescence and young adulthood, then plateaus or modestly declines after midlife. The facets within Openness move somewhat independently: intellectual curiosity tends to hold steady, while openness to new experiences may decline.

Extraversion is more stable but not static. Social dominance (assertiveness, leadership) increases through midlife, while social vitality (enthusiasm, sociability) may decrease slightly in older adulthood.

The overall picture: people tend to mature. They become more emotionally stable, more responsible, and more agreeable over time. Researchers call this the "maturity principle" of personality development (Roberts & Wood, 2006).

What Drives Personality Change

Personality change isn't random. Several specific drivers have been identified in the research.

Taking on new social roles, becoming a parent, starting a career, entering a committed relationship, drives corresponding personality changes. Roberts, Wood, and Smith (2005) found that investment in work was associated with increases in Conscientiousness, and investment in romantic relationships was associated with decreases in Neuroticism. The mechanism is behavioral: new roles demand new behaviors, and sustained behavioral change gradually shifts the underlying trait.

Major Life Events

Significant life events can produce measurable personality change. Luhmann, Orth, Specht, Kandler, and Lucas (2014) examined the effects of events like marriage, divorce, unemployment, and widowhood on personality. Marriage was associated with decreases in Neuroticism. Unemployment was associated with decreases in Agreeableness and Conscientiousness. The effects weren't enormous, but they were reliable.

Deliberate Effort and Therapy

This is the finding that matters most for anyone reading this article. Roberts and colleagues (2017) conducted a meta-analysis of 207 studies examining whether clinical interventions change personality. The answer was clear: yes. Therapy produced measurable changes in personality traits, with the largest effects on Neuroticism (which decreased) and Extraversion (which increased).

The effect sizes were clinically meaningful. The average intervention lasted about 24 weeks and produced changes equivalent to half the amount of naturally occurring personality change that happens over a lifetime. In other words, a few months of therapy can produce personality shifts that would otherwise take decades.

Notably, the changes were not specific to any one type of therapy. Cognitive-behavioral therapy, psychodynamic therapy, and other modalities all produced personality change. The most parsimonious explanation is that any sustained therapeutic process that helps people regulate emotions, develop insight, and practice new behaviors can shift personality traits.

Volitional Change

Can you change your personality simply by deciding to? Hudson and Fraley (2015) found that people who set specific goals to change a Big Five trait, and actively worked on those goals, showed measurable trait change over a 16-week period. The changes were small but statistically significant and directionally consistent with goals. People who wanted to become more extraverted did become slightly more extraverted. Those who wanted to become more conscientious did become slightly more conscientious.

The caveat: sustained, deliberate effort was necessary. Simply wanting to change without behavioral follow-through didn't produce results.

How Much Change Is Typical?

It helps to calibrate expectations. Here's what the research suggests about the magnitude of personality change.

Over a decade: Personality traits change by roughly 0.3-0.5 standard deviations for the average person between ages 20 and 30. The rate slows after 30 but doesn't stop.

Over a lifetime: Cumulative change from early adulthood to old age averages about 1 standard deviation across traits. That's substantial. A person one standard deviation higher in Conscientiousness would be noticeably more organized, reliable, and self-disciplined.

Through therapy: The Roberts et al. (2017) meta-analysis found average personality change of approximately 0.4 standard deviations over 24 weeks of treatment. Neuroticism showed the largest changes (d = 0.57).

Through self-directed effort: Smaller effects, roughly 0.1-0.2 standard deviations over 16 weeks, per the Hudson and Fraley (2015) findings. Meaningful but modest.

The bottom line: personality change is real, measurable, and practically significant. It's also gradual. Expecting to overhaul your personality in a month is unrealistic. Expecting meaningful shifts over a year or two, especially with structured support, is well-grounded.

What Doesn't Change

Some aspects of personality are more resistant to change than others.

Rank-order stability increases with age. Your position relative to other people on a given trait becomes more stable over time. It's easier to shift your traits at 25 than at 55. Not impossible at 55, just harder.

Core temperamental tendencies have a genetic floor. Twin studies consistently show that Big Five traits are 40-60% heritable (Bouchard & Loehlin, 2001). You can't will your way out of a genetic predisposition toward high Neuroticism. You can, however, learn to manage it, reduce its intensity, and change how it manifests in your behavior.

Trait profiles tend to maintain their shape. If you're higher in Openness than Conscientiousness, you'll likely maintain that relative pattern even as both traits shift. Change tends to be more about moving the entire profile up or down than about radically reshaping it.

Frequently Asked Questions

Is personality really "set by 30"?

No. This idea, often attributed to William James, has been contradicted by decades of longitudinal research. Personality continues to change throughout adulthood. The rate of change does slow after 30, but meaningful shifts occur at every stage of life. Roberts et al. (2006) found significant personality change in every decade from the teens through the 70s.

Can trauma change your personality?

Yes, though the effects are complex. Trauma, particularly sustained or severe trauma, can increase Neuroticism and decrease Agreeableness and Conscientiousness. Post-traumatic stress disorder (PTSD) is associated with measurable shifts in personality traits (Lofgren, Claeson, & Diehm, 2022). However, some people experience post-traumatic growth, emerging from difficult experiences with increased Openness, stronger values, and greater emotional maturity. The trajectory depends on the nature of the trauma, available support, and individual resilience factors.

If I take a personality test now and again in 5 years, will my results be different?

Probably somewhat, yes. Test-retest correlations over 5 years are typically in the r = 0.65-0.80 range for the Big Five. Your overall profile will likely be recognizable, but specific trait scores may shift by several percentile points. This is normal and reflects genuine personality development, not measurement error.

What to Do Next

If you're curious about where your personality stands right now, a baseline measurement gives you something concrete to work with. Whether you're interested in understanding your current traits, tracking change over time, or identifying areas where deliberate development might be valuable, the starting point is the same.

Take the Big Five Assessment to measure your current standing on all five traits, including the facet-level detail that captures where within each trait your strengths and growth areas live.

Citations

Bouchard, T. J., & Loehlin, J. C. (2001). Genes, evolution, and personality. Behavior Genetics, 31(3), 243-273.

Hudson, N. W., & Fraley, R. C. (2015). Volitional personality trait change: Can people choose to change their personality traits? Journal of Personality and Social Psychology, 109(3), 490-507.

Luhmann, M., Orth, U., Specht, J., Kandler, C., & Lucas, R. E. (2014). Studying changes in life circumstances and personality: It's about time. European Journal of Personality, 28(3), 256-266.

Roberts, B. W., & Wood, D. (2006). Personality development in the context of the neo-socioanalytic model of personality. In D. K. Mroczek & T. D. Little (Eds.), Handbook of personality development (pp. 11-39). Lawrence Erlbaum.

Roberts, B. W., Walton, K. E., & Viechtbauer, W. (2006). Patterns of mean-level change in personality traits across the life course: A meta-analysis of longitudinal studies. Psychological Bulletin, 132(1), 1-25.

Roberts, B. W., Wood, D., & Smith, J. L. (2005). Evaluating Five Factor Theory and social investment perspectives on personality trait development. Journal of Research in Personality, 39(1), 166-184.

Roberts, B. W., Luo, J., Briley, D. A., Chow, P. I., Su, R., & Hill, P. L. (2017). A systematic review of personality trait change through intervention. Psychological Bulletin, 143(2), 117-141.

Part of the Understanding Your Personality guide. For a deeper dive into each trait, see the Big Five Personality Traits Guide.

Your True Self is an informational and self-reflection tool. It is not a clinical assessment, psychological evaluation, or substitute for professional mental health services.