When we examined cases of MDD we found that higher neuroticism scores significantly increased the risk for the number of comorbid disorders (OR = 1.13), the number of MDD episodes (OR = 1.07), and the number of depressive symptoms (OR = 1.08) (Table 2). Using linear regression, we found a highly significant relationship between neuroticism and the age at onset of MDD (P value < 1 × 10− 14); neuroticism explained 3% of the variance in age of onset. Neuroticism scores were also modestly related to the maximal duration of episodes (P value = 0.004) explaining ~ 0.5% of the variance.
