We recently reported (EPA 2011) that one factor of the Eysenck Neuroticism Scale (EPI-N) represents Mood Instability (MI) that was a significant predictor of suicidal thoughts.

To increase our understanding of MI in psychological distress we examined a national sample with longitudinal follow-up:

1. 1. To determine whether factor analysis of the EPI-N scale yields a MI factor.

2. 2. To determine whether the MI factor predicts psychological well-being at follow-up.

British Health and Lifestyle survey (1984) (N = 6,124) individuals that completed both of the following questionnaires. 3,232 individuals were followed in 1991–92.

Eysenck Personality Inventory consists of 57 items that includes the EPI-N with 24 items. The General Health Questionnaire (GHQ) is a 30-item scale used to measure psychological distress in the community.

The EPI-N was factor analyzed and the extracted factors were entered as predictors of GHQ (1991) in a linear regression model, while controlling for baseline (1984) GHQ score and important physical health and socio-demographic variables.

We replicated the 3 factors of the EPI-N, the second factor represented MI. The other two factors represented mild symptoms of anxiety and depression. The 3 EPI-N factors (Including the MI factor), GHQ, hypertension and forced expiratory volume (1984) predicted GHQ (1991). Age, sex, marital status, occupational class, and household income were not predictors.

MI is the salient and distinct feature of neuroticism. MI may be a more clinically and empirically useful concept than “neuroticism” and is a fertile subject for clinical and basic research.