Therapy experience in naturalistic observational studies is associated with negative changes in personality

•Examined association between personality trait change and therapy experience.•Propensity score matching used to compare those with/without therapy experience.•Therapy experience associated with significant increase in undesirable traits.•Therapy experience associated with significant decrease in desirable traits.•Pattern of findings replicated across two large samples in U.S. and Germany.

Recent research has shown that personality traits change as a result of clinical therapy, although evidence for this effect is derived from efficacy studies that reflect relatively controlled experimental designs. Little is known about how therapy in real world contexts affects change in personality. In two longitudinal studies (N's = 1270 and 5217), the present research examined whether personality trait change was associated with therapy experience. Propensity score matching was used to compare trajectories of personality trait change in individuals with and without therapy experiences. Overall, therapy experiences were associated with significant increases in undesirable traits and markers (e.g., chronic stress, depression, neuroticism), and significant decreases in desirable traits (e.g., self-esteem, conscientiousness).