Many patients with depression mention sudden short “mood swings” (MI) when asked. MI is distressing but little is known about its relationship to personality disorders, depression and suicidal thoughts.

To determine the relationship between mood instability (MI), neuroticism, and suicidal thoughts.

To deconstruct the concept of neuroticism to determine whether MI is an important component. To determine whether MI predicts suicidal thoughts.

129 patients with Major Depression were interviewed with the MINI diagnostic interview. They also completed the Eysenck Neuroticism Scale (ENS), Beck Depression Inventory (BDI), Mood Disorders Questionnaire (MDQ), Perceived Stress Scale (PSS), Affective Lability Scale (ALS), Beck Suicide Scale (BSS) and 5 questions describing mood swings and its effects on behaviour.

In a regression analysis with the BSS as the dependent variable, with age and sex controlled, and all of the other variables entered, only the BDI (p < 0.001) and the ALS (p < 0.01) were significant predictors. In an exploratory factor analysis of the ENS, 3 main factors (53% of variance) emerged. 2 of the factors consisted of mild anxiety and depression symptoms. The third factor (16% variance) was a mood instability factor. The ALS and the ENS both correlated with the 5 questions describing mood swings, but the correlations with the ALS were stronger.

Mood Instability is the unique component of neuroticism. MI (ALS) predicts suicidal thoughts along with the broad concept of depression (BDI). In this model, neuroticism (ENS) is not a predictor.