Trichotillomania (TTM) is an obsessive-compulsive spectrum disorder characterized by repetitive hair pulling that results in significant hair loss (American Psychiatric Association [APA], 2022). TTM is associated with considerable distress, psychosocial impairment, and lower quality of life (Grant et al., 2016; Valle and Grant, 2022), and affects between 1.1 and 1.8% of adults. Prevalence rates may be similar in men and women (Grant et al., 2020; Thomson et al., 2022).

Behavior therapy with habit reversal training (HRT; Azrin and Nunn 1973) has been the most empirically-supported treatment approach for TTM (Farhat et al., 2020). HRT involves awareness training, competing response training, and social support training (Woods and Twohig, 2008). In addition to HRT, behavior therapy protocols for TTM often also include stimulus control procedures, which involve identifying environmental factors that increase the likelihood of pulling and altering them to decrease the behavior (e.g., limit time spent in the bathroom, cover mirrors).

Small studies testing HRT for TTM have found short-term success in reducing symptom severity (Bloch et al., 2007; Farhat et al., 2020; Lee et al., 2019; McGuire et al., 2014; Slikboer et al., 2017). However, longer-term follow-up data indicates that relapse is common. In this context, “relapse” is typically defined as a significant increase in TTM symptoms from post-treatment to follow-up, or as no longer meeting criteria for treatment response at follow-up (Falkenstein et al., 2014; Keijsers et al., 2016). For example, in a stepped-care behavior therapy study with 60 patients, 36% initially showed a clinically significant response, but only 17% were responders at a 3-month follow-up (Falkenstein et al., 2014). Likewise, a study of cognitive-behavioral therapy (CBT) for TTM found that 31% of treatment completers (n=14) were considered clinical responders at follow-up (M=3.75 years), compared to 86% at post-treatment (Lerner et al., 1998). In another behavior therapy study for TTM, while 79% of participants (n=28) showed clinical improvement post-treatment, only 38% of participants assessed 2 years later showed clinical improvement (Keijsers et al., 2006).

Reasons for relapse following behavioral interventions for TTM are unclear, but one possibility is that typical behavior therapy procedures (e.g., HRT, stimulus control) do not fully address significant factors contributing to pulling. For example, HRT directly targets the act of pulling but does not address internal environmental variables such as emotions, urges, thoughts, and beliefs. These internal experiences may not dissipate from HRT and stimulus control strategies designed to reduce pulling behaviors. As emotions, urges, thoughts, and beliefs often trigger pulling and can contribute to symptom maintenance (Rehm et al., 2015; Roberts et al., 2013), if left untreated, their presence may increase vulnerability to relapse.

Accordingly, efforts to enhance HRT have focused on integrating techniques from other therapies that more directly target aversive internal experiences. For example, several studies incorporated dialectical behavior therapy (DBT) with HRT and demonstrated its efficacy in reducing TTM symptoms and impairment (Keuthen et al., 2010, 2011, 2012). Improvements from DBT-enhanced behavior therapy may be durable, as evidenced by a study where 9 of 10 participants met full or partial responder status 6 months post-treatment (Keuthen et al., 2011). In another trial of DBT-enhanced behavior therapy, TTM symptom severity significantly improved from pre-treatment to 6-month follow-up, although symptoms did increase from post-treatment to follow-up (Keuthen et al., 2012). Comprehensive behavioral therapy (ComB; Mansueto et al. 1997) is another treatment approach for TTM, which addresses patients’ individualized pulling triggers across five domains: sensory, cognitive, affective, motor, and place/environment. In an RCT of ComB, improvements in post-treatment symptom severity were maintained at a 6-month follow-up, but clinical response rates were 35% at post-treatment and 20% at follow-up (Carlson et al., 2021). Another line of research combined HRT techniques with acceptance and commitment therapy (ACT; Hayes et al. 1999). ACT is based on the premise that psychological distress is largely tied to experiential avoidance, or a tendency to escape or control unwanted internal experiences (e.g., emotional states, cognitions, urges). Key objectives of ACT are to increase psychological flexibility toward unpleasant private experiences and reduce ineffective attempts at controlling emotions and thoughts.

A growing body of research supports the efficacy of acceptance-enhanced behavior therapy for TTM (AEBT-TTM; Woods and Twohig 2008). AEBT-TTM trials have found success in reducing TTM symptoms in adults (Lee et al., 2018a, 2018b; Twohig and Woods, 2004; Woods et al., 2006) and adolescents (Fine et al., 2012; Petersen et al., 2022). A meta-analysis of randomized controlled trials (RCT) testing behavior therapy for TTM found stronger effect sizes for enhanced behavior therapy (i.e., AEBT-TTM or DBT-enhanced) as compared to behavior therapy alone (McGuire et al., 2014). In a recently published RCT, Woods et al. (2022) compared the efficacy of AEBT-TTM to a psychoeducation and supportive therapy (PST) control condition in a sample of adults with TTM who received 10 sessions of treatment over 12 weeks. Results immediately following treatment showed that AEBT-TTM yielded higher treatment response rates (odds ratio=4.0) and greater decreases in TTM symptom severity (NIMH-TSS effect size =.59; MGH-HS effect size=0.46).

Data from prior studies also suggest that AEBT-TTM may have more durable treatment effects. For example, a small randomized trial of AEBT-TTM showed that improvements in TTM impairment and daily pulling frequency were maintained from post-treatment to 3-month follow-up, although symptom severity did increase during this time period (Woods et al., 2006). In another study, three out of four participants who received AEBT-TTM maintained their treatment gains 3 months later (Twohig and Woods, 2004). Further, group AEBT-TTM led to significant reductions in TTM symptoms from pre-treatment to one-year follow-up, and 63% of participants were clinical responders one year post-treatment (Haaland et al., 2017). Studies examining AEBT-TTM delivered via telehealth demonstrated that symptom improvements were maintained 3 months (Lee et al., 2018a) and one year following treatment (Petersen et al., 2022). However, no studies have examined long-term outcomes of AEBT-TTM compared to a credible therapeutic control.

Given the high relapse rate in TTM, it is also important to identify predictors of long-term treatment outcome. Prior behavior therapy studies suggest better maintenance of gains in those with lower baseline TTM symptoms (Lerner et al., 1998), lower TTM symptoms at initial treatment response (Falkenstein et al., 2014), and lower baseline depression symptoms (Keijsers et al., 2006; Lerner et al., 1998). Predictors of long-term gain maintenance from AEBT-TTM have not yet been investigated, but it is plausible that factors associated with long-term outcome in behavior therapy for TTM may also be relevant for AEBT-TTM. Additionally, having a comorbid disorder predicted worse long-term treatment outcomes in related disorders (Jakubovski et al., 2013) and has been linked to more severe TTM symptoms (Lochner et al., 2019) which might suggest that having a current comorbid disorder could be important to examine as a potential predictor of long-term symptom improvement in TTM.

The current study aimed to examine the durability of TTM intervention using 6-month controlled follow-up data from the Woods et al. (2022) RCT comparing AEBT-TTM to an active psychoeducation and supportive therapy control (PST). Additionally, we explored baseline TTM severity, post-treatment TTM symptom severity, baseline depression level, and presence of a comorbid condition as potential predictors of treatment outcomes at 6 months follow-up, based on the aforementioned research suggesting that these factors may be associated with long-term gain maintenance.