Why are people neurotic?
Psychologists have long thought of neuroticism as a fundamentally maladaptive personality trait. Neurotics experience a preponderance of negative emotions, get sick frequently, and tend to lack satisfying interpersonal relationships. In short, neuroticism seems devoid of any redeeming value. An evolutionary perspective, however, would suggest that all human characteristics must have been passed on through natural selection, meaning that even neuroticism must have somehow helped people survive and reproduce throughout history.
What benefit might neuroticism have? Recently, Daniel Nettle (2006; American Psychologist) theorized some benefits that the avoidance-oriented aspects of neuroticism might have. He noted that neurotics might be more wary of dangers in their environment and that they might be more sensitive to internal disturbances (for example, noticing that they feel sick). Similarly, we might hypothesize that approach-oriented tendencies, such as aggression and emotional outbursts, might help neurotic individuals gain status or attention (for example, through intimidation).
Does neuroticism, and the negative emotionality that comes with it, really have an upside? While you ponder that question, think about the parallel question for each Big Five trait (extraversion, conscientiousness, agreeableness, openness to experience); do both high and low levels of these traits benefit people in some way? The answer will help us understand the deeper adaptive significance of personality.