From Ars Technica: A recent meta-analysis found that a variety of different therapeutic techniques result in positive personality changes. The two personality traits most impacted by therapy were extraversion and neuroticism.
“Aside from the evidence this provides for the merits of therapy, the results also help with our understanding of personality change. The accepted idea, the researchers write, is that personalities ‘typically change slowly and incrementally.’ But this evidence suggests that personality change could be quite fast at times. It’s possible that people undergo periods of more dramatic change, with stasis in between, rather than experience a gradual drift over time. That’s a question that future research will need to answer, because studies looking at personality change typically haven’t surveyed people often enough to provide data on this.”