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

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Highlights

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    Sensitivity to reward and punishment predict hair-pulling in a non-clinical cohort.

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    Sensitivity to punishment and depression predict clinical severity hair-pulling.

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    The reward sensitivity theory of personality traits are relevant to hair-pulling.

Abstract

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.

Section snippets

. Introduction

An individual experiencing trichotillomania (TTM), otherwise known as compulsive hair pulling, would typically pull out individual hairs one at a time over extended periods. TTM is listed within the Obsessive Compulsive and Related Disorders diagnostic group in the DSM 5 (American Psychiatric Association, 2013). Typically, without treatment, TTM is chronic, with fluctuating severity over decades (American Psychiatric Association, 2013). It influences many psychosocial elements of life,

Procedure

Participants for study 1 were recruited via postings of an anonymous online questionnaires on social media, and on websites that individuals with trichotillomania and related disorders frequent such as, online support groups, and sites with information about trichotillomania and related disorders. First year psychology students from the University were invited to participate for course credit. Once clicking the link participants read an informed consent document and were able to decide to

Measures

The Massachusetts General Hospital Hair Pulling Scale (MGH; Keuthen et al., 1995) is a self-report measure of trichotillomania symptom severity over the prior week. The MGH-HPS asks about three areas: three questions regarding the urge to pull hair; three questions about the actual hair pulling and one question about the consequences of hair pulling. The scale has acceptable reliability (α = 0.89) and test-retest over an hour. Convergent and divergent validity have been established (Keuthen et

Statistical analysis plan

For study 1, a MANOVA was conducted to test whether there were differences between those with and without hair-pulling symptoms on key RST traits: sensitivity to reward (SR), sensitivity to punishment (SP), and levels of the behavioural inhibition system (BIS) and behavioural activation system (BAS).

For studies 2 and 3, a stepwise discriminate function analysis was conducted to explore which, (if any) RST traits and levels of depression and anxiety could predict group membership, and further,

Participants

A total of 389 participants were included across the three studies; study 1 (n = 295), study 2 (n = 50) and study 3 (n = 44). Table 1 shows the distribution of participants across the three studies, demographic information and hair-pulling severity.

Participants for study 1 provided self-reported diagnoses received from a health care professional. Overall, those in the healthy control group reported less diagnosis than those in the group with hair-pulling symptoms. Participants for study 2

Discussion

This study explored the question of whether there could be a relationship between RST and hair pulling behaviour. Study 1 indicated average levels of sensitivity to punishment and reward where higher in those with non-clinical TTM than healthy controls. Firstly, people who reported varying levels of hair pulling symptoms on average tended to score higher on sensitivity to reward, measured by the BAS scale, and higher on sensitivity to punishment, measured by the SP scale, than those who were

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