Neurobiology of trichotillomania

Trichotillomania (TTM) is a common debilitating impulse control disorder, which is under-recognized in clinical practice. New research shows interesting similarities between TTM, other impulse control disorders, and obsessive–compulsive disorder (OCD), while also revealing important differences in some endophenotypic measures. In this chapter we review new advances in genetic, family, neurocognitive, neuroimaging, and neuropharmacological studies. Neural abnormalities in the amygdalo–hippocampal formation and frontal–subcortical circuits are discussed. Animal models of hair pulling are also outlined and may prove a fruitful avenue for future research. Introduction Trichotillomania is a neuropsychiatric disorder characterized by noticeable hair loss due to a recurrent failure to resist impulses to pull out hairs. The hair pulling is usually preceded by mounting tension and followed by a sense of relief or gratification (WHO 2002). It predominantly affects females (Swedo and Leonard 1992), and its onset is usually in late childhood and adolescence (Walsh and McDougle 2001). A subgroup with very early onset of hair pulling in children under the age of six may be more benign and self-limiting (Keren et al . 2006). Often accompanied by shame and distress, TTM is under-recognized in clinical practice and its prevalence is likely to be greater than currently understood (Bohne et al . 2005b). There have been no population-based epidemiological studies of TTM. In a sample of 2579 college students in the United States, a lifetime prevalence of TTM was seen in 0.6%, though subthreshold symptoms not reaching diagnostic criteria were identified in 1.5% of males and 3.4% of females (Christenson et al . 1991b).