A longitudinal study of more than 20,000 Swedish twins has found the personality trait of neuroticism is a strong predictor of the development of major depression later in life.
Between 1972 and 1973, the twins answered questionnaires related to neuroticism and extroversion in their personalities. More than 25 years later, the twins were personally interviewed to see if they had developed depression over the course of their lives.
While extroversion appeared to have little connection to depression, neuroticism strongly predicted later developing its symptoms. Analysis between the twins additionally showed that both neuroticism and depression were largely genetically correlated, suggesting shared genetic risk factors lead to depression.
ABSTRACT: Personality and Major Depression