Abnormal weight has also been associated with trait Neuroticism. Individuals who are underweight tend to score higher in proneness to negative affect than those who are in the normal weight range (Kakizaki et al., 2008; Terracciano et al., 2009). Similarly, in clinical populations, underweight individuals and those with eating disorders tend to score higher in Neuroticism (Bulik et al., 2006; Cassin & Von Ranson, 2005). On the other side of the BMI continuum, overweight and obese groups tend to have a higher prevalence of psychiatric disorders (Petry, Barry, Pietrzak, & Wagner, 2008), which suggests that such groups may also score higher on Neuroticism. Neuroticism may be associated with both ends of abnormal weight for at least two reasons: There could be a curvilinear relation between weight and Neuroticism, such that both ends of the BMI continuum are associated with higher Neuroticism and/or different aspects of Neuroticism may be associated with being overweight or underweight (see below).
