Obsessive-Compulsive Personality Disorder (OCPD) is characterized by a pervasive pattern of preoccupation with orderliness, perfectionism, and a need for mental and personal control. Although it shares certain rigid and stereotyped beliefs and behaviors with Obsessive-Compulsive Disorder (OCD), particularly concerning cognitive inflexibility and perfectionism, OCPD differs in that it lacks the intrusive obsessions and compulsive behaviors typical of OCD (Mancebo et al., 2005). Furthermore, while in OCD these behaviors are ego-dystonic and restricted to specific areas of life, in OCPD they are ego-syntonic and pervasively affect the individual's overall functioning (Mancebo et al., 2005). On the other hand, levels of insight into the disorder differ between OCD and OCPD. Individuals with OCD typically recognize their symptoms as irrational and distressing, prompting them to seek relief, whereas those with OCPD often lack such awareness, perceiving their behaviors as appropriate and consistent with their self-identity (Mancebo et al., 2005).

The relationship between OCD and OCPD has been debated for over a century. Pierre Janet first proposed that obsessive personality traits were precursors to OCD (Janet, 1906). Similarly, Freud suggested that traits associated with the “anal-erotic” character, such as orderliness and parsimony, predispose individuals to the onset of OCD (Freud, 1908). Although subsequent investigation reported that obsessive traits were not over-represented in patients with obsessive neurosis (Pollack, 1979) and that obsessive personality and obsessive neurosis were distinct entities (Pollack, 1987), recent research has continued to support a link between OCD and OCPD (Wheaton et al., 2022).

OCPD is the most prevalent personality disorder among patients with OCD, with studies reporting its presence in up to 43.7% of cases (Sadri et al., 2017). A recent meta-analysis reported comorbidity rates between OCD and OCPD of 25% (Pozza et al., 2021). Additionally, family studies have found a significant prevalence of obsessive-compulsive personality traits in the parents of children with OCD (Lenane et al., 1990), and relatives of OCD patients show twice the prevalence of OCPD compared to control groups (Samuels et al., 2000). Given the evidence of a close link between the two disorders, it has been also hypothesized that OCD with comorbid OCPD may represent a distinct and more severe subtype of OCD (Coles et al., 2008), much like tic-related OCD, which was introduced as a specifier in the DSM-5 and is associated with specific clinical features and treatment challenges (APA, 2013; Benatti et al., 2021).

The majority of literature suggests that the presence of OCPD in patients with OCD is associated with specific characteristics, such as a poorer social functioning (Denys et al., 2004; Garyfallos et al., 2010; Lochner et al., 2011), an earlier onset of OC symptoms (Coles et al., 2008; Garyfallos et al., 2010), a greater chronicity, and higher rates of comorbidities Coles et al. (2008); Nestadt et al. (2009); Lochner and Stein, 2010). Additionally, patients with both conditions were found to show more symmetry and hoarding obsessions, and compulsions related to cleaning, ordering, repeating, and hoarding (Coles et al., 2008), as well as higher rates of comorbidity and reduced insight compared to patients with OCD alone (Lochner et al., 2011).

In terms of therapeutic approaches, while current guidelines for the treatment of OCD recommend the use of SSRIs in combination with cognitive-behavioral therapy (CBT; APA, 2007), conflicting results have been reported on the impact of OCPD on treatment outcomes and the severity of OCD. Indeed, some studies have found that OCPD does not negatively impact treatment response (Baer and Jenike, 1992; Fricke et al., 2006; Sadri et al., 2017), particularly from a psychotherapeutic perspective (Gordon et al., 2016). However, other reports suggest that OCPD traits may lead to poorer outcomes in relation to pharmacological and psychotherapeutic response (Cavedini et al., 1997; Pinto et al., 2011; Simpson et al., 2021; Wetterneck et al., 2011). It has been hypothesized that the ego-syntonic traits associated with OCPD may encourage patients to persist in dysfunctional behaviors and delay help-seeking (Luo et al., 2020). In addition, it has been reported that a longer duration of untreated illness (DUI) predisposes individuals to a poorer treatment response, persistent, severe symptoms, and lower remission rates (Dell’Osso et al., 2010; Dell’Osso et al., 2017; Albert et al., 2019; Fineberg et al., 2019; Perris et al., 2023).

Regarding the severity of OCD with comorbid OCPD, literature remains inconsistent. Most studies report greater OCD symptom severity in patients with comorbid OCPD (Lochner et al., 2011; Gordon et al., 2013), while a recent meta-analysis suggests the opposite (Pozza et al., 2021). Moreover, previous studies found no significant impact of OCPD on the severity of OCD symptoms (Diaferia et al., 1997; Coles et al., 2008).

To date, while both OCD and OCPD have been extensively studied, the impact of comorbid OCPD on OCD remains underexplored and results in the field are mixed. Therefore, the present study aims to investigate potential differences in psychopathological characteristics between OCD patients with and without comorbid OCPD.