Motivation underlying hair-pulling behaviour conceptualized by the reinforcement sensitivity theory of personality

Trichotillomania (TTM) is postulated to be a disorder in which both impulsivity, motivated by reward, and compulsivity, motivated by punishment, contribute equally. Three separate studies were conducted to measure response to reward and punishment within the context of the reinforcement sensitivity theory of personality to examine whether hair-pulling behaviours could be predicted by sensitivity to reward and/or punishment. For study 1, a MANOVA was conducted to identify differences in sensitivity to reward and punishment in a cohort recruited via the internet, with hair-pulling symptoms (n = 89) and without symptoms (n = 206). For study 2, a stepwise discriminate function analysis was conducted to assess whether sensitivity to reward and punishment, along with anxiety and depression could predict group membership (in n = 25 individuals with hair-pulling symptoms and n = 25 without symptoms). Study 3 attempted to replicate the results of study 2 in a cohort of individuals who met clinical diagnostic criteria for trichotillomania (n = 22) and healthy controls (n = 22). It was concluded that both sensitivity to reward and sensitivity to punishment drive the motivation for hair-pulling in non-clinical samples. When participants met diagnostic criteria for TTM, depression and sensitivity to punishment became more important.