Defining Neuroticism and What It Comprises
Neuroticism is one of the five factors of the Big Five model, and it is the dimension that measures a person's tendency to experience negative emotion. In the NEO-PI-R it is made up of six subscales: anxiety, angry hostility, depression, self-consciousness, impulsiveness and vulnerability. Those high in neuroticism show strong emotional reactions to stressful situations, are prone to feeling anxiety or anger even over minor events, and take longer to recover from negative emotional states. What matters is that neuroticism is not itself a mental disorder. It is a normal dimension of personality expressing individual differences in sensitivity to negative emotion. That said, when it is extremely high it does constitute a risk factor for anxiety disorders and depression.
Emotional Instability and Vulnerability to Stress
High neuroticism is bound up with the intensity of a person's physiological and psychological responses to stress. In the theory advanced by Hans Eysenck, neuroticism was taken to reflect individual differences in the reactivity of the limbic system, and of the amygdala in particular. Findings from neuroscience are consistent with this picture, showing that people high in neuroticism exhibit stronger amygdala activation in response to threatening stimuli, together with comparatively weaker emotional regulation by the prefrontal cortex. Vulnerability to stress appears not only as the experience of more acute distress in response to the same stressor, but also as a cognitive bias towards interpreting even neutral stimuli as threatening. In the interpersonal domain this surfaces as a tendency to read a partner's neutral behaviour, such as a slow reply or a stiff expression, in a negative light, and it becomes a source of conflict that need never have occurred.
Neuroticism and the Quality of a Relationship
Of the five Big Five factors, neuroticism is the strongest negative predictor of relationship satisfaction. Meta-analyses indicate that high neuroticism lowers not only a person's own relationship satisfaction but also that of their partner, an outcome known as a partner effect. This happens because people high in neuroticism express negative emotion frequently, treat minor problems as large ones, and are more likely to adopt critical patterns of communication. Couple studies find the quality of the relationship to be lowest where neuroticism is high in both partners, since such couples fall readily into a vicious cycle of negative interaction. Even so, research shows that the impact can be moderated where high-neuroticism individuals acquire emotional regulation skills, or where their partner has a secure attachment style. A neuroticism score is therefore worth reading as something more than simply high or low. Taken together with how a person recovers once they feel overwhelmed, and with how the two of you speak to each other under strain, the same score can mean quite different things.