Low affective temperament consistency during development: Results from a large retrospective study.

Background: Temperament is still regarded as a stable part of personality, an "endophenotype" developed early in life. However, how frequently temperament traits can change throughout life is not clear. The aim of this study was to investigate affective temperament changes from late childhood to adolescence and from late adolescence to adulthood.

Methods: We used data from a cross-sectional web-based survey collected from the Brazilian Internet Study on Temperament and Psychopathology. We used the Affective and Emotional Composite Temperament Scale questionnaire to assess temperament at time of participation, and at age of 10-12 and 18 years, retrospectively, dividing affective temperaments into four major groups: internalized, externalized, stable and unstable. The final sample consisted of 36,255 participants from 24 to 40 years of age (71.9% women).

Results: Most of the sample (66.2%) changed to a different affective temperament group at adulthood. We found a significant decrease in internalized temperaments from 10-12 to 18 years of age (34.5% to 25.0% in women and 31.8% to 26.7% in men), parallel with an increase of externalized temperaments (14.1% to 20.3% in women and 17.3% to 19.6% in men). From 18 years of age to adult life, stable temperaments decreased slightly in frequency (37.9% to 32.5% in women and 38.6% to 36.8% in men), while unstable types increased (16.9% to 24.0% in women and 15.3% to 18.4% in men).

Limitations: The retrospective design and self-reported evaluation may bias self-perception.

Conclusions: Affective temperaments often change over time, contrary to the classic view of temperament as a consistent phenotype.