In the study of psychology, neuroticism has been considered a fundamental personality trait. In the Big Five approach to personality trait theory, individuals with high scores for neuroticism are more likely than average to be moody and to experience such feelings as anxiety, worry, fear, anger, frustration, envy, jealousy, pessimism, guilt, depressed mood, and loneliness. Such people are thought to respond worse to stressors and are more likely to interpret ordinary situations, such as minor frustrations, as appearing hopelessly difficult. The responses can include maladaptive behaviors, such as dissociation, procrastination, substance use, etc., which aids in relieving the negative emotions and generating positive ones.
People with high scores on the neuroticism index are thought to be at risk of developing common mental disorders (mood disorders, anxiety disorders, and substance use disorders have been studied), and the sorts of symptoms traditionally referred to as "neuroses".
Neuroticism is a trait in many models within personality theory, but there is significant disagreement on its definition. It is sometimes defined as a tendency for quick arousal when stimulated and slow relaxation from arousal, especially with regard to negative emotional arousal. Another definition focuses on emotional instability and negativity or maladjustment, in contrast to emotional stability and positivity, or good adjustment. It has also been defined in terms of lack of self-control, poor ability to manage psychological stress, and a tendency to complain.
Various personality tests produce numerical scores, and these scores are mapped onto the concept of "neuroticism" in various ways, which has created some confusion in the scientific literature, especially with regard to sub-traits or "facets".
Individuals who score low in neuroticism tend to be more emotionally stable and less reactive to stress. They tend to be calm, even-tempered, and less likely to feel tense or rattled. Although they are low in negative emotion, they are not necessarily high in positive emotion.