Obsessive-compulsive disorder (OCD) is a disorder characterized by obsessions and compulsions. Obsessions are thoughts, images and/or impulses that come involuntarily and disturb the person. Compulsions refer to repetitive behavioral or mental processes to get rid of this feeling of discomfort [1].

Mental contamination is defined as the experience of feeling dirty and unclean despite not being in contact with a physical contaminant [2]. Its source is mostly subjective negative interpretations of internal experiences such as thoughts, emotions, sensations and mental images. It may also originate from emotional and/or physical traumatic experiences such as humiliation, betrayal, cruel criticism, abuse [3,4]. Negative and excessive self-evaluations, which may also include the thought that they cannot adequately defend themselves, may pave the way for the development of mental contamination. Feelings of disgust, shame and self-disgust may lead to repetitive cleaning and washing behaviors [5]. Although the most common behavior is washing hands, this is usually not helpful because mental contamination is internal, pervasive and inaccessible. In these aspects, mental contamination has a different and distinct structure from contact contamination, although it has similar aspects and can be seen together. Although it is understood that mental contamination has a transdiagnostic basis and is associated with various psychopathologies such as eating disorders, post-traumatic stress disorder (PTSD), anxiety, depression and phobias, it is stated that it shows the strongest relationship with OCD symptoms [2,3]. Research indicates that around 46% of individuals diagnosed with OCD report experiencing mental contamination [3]. In recent studies, mental contamination has started to be discussed as an important factor in understanding and treating the OCD clinic [5]. On the other hand, mental contamination can also be seen in the non-clinical population [4]. Unlike pathologic mental contamination seen in clinical conditions, mental contamination seen in healthy individuals is triggered intermittently by reminders and then passes, is tolerable, and does not impair functionality.

Childhood traumas can be seen more frequently in OCD cases. A systematic review of studies including clinical and non-clinical samples found evidence of a significant association between exposure to childhood trauma and OCD symptom severity [6]. However, these findings included different types of childhood traumas rather than a single type of trauma [6]. A recent study by Corkish and Yap [7] showed that the relationship between childhood trauma and OCD can be explained through mental contamination. Childhood traumas may bring about a series of excessive negative self-evaluations and internalized feelings of contamination in which the person blames himself/herself and feels inadequate.

Alexithymia is defined as difficulty in recognizing and expressing emotions. Difficulty in emotional regulation negatively affects social functioning. Alexithymia, which can be seen in the general population, is also considered as a risk factor and/or consequence of many mental illnesses. Although there are studies showing the relationship between OCD and alexithymia in the literature, no study investigating the relationship between alexithymia and mental contamination, which is predicted to frequently accompany OCD, has been found [8-10].

Our study aims to contribute to the diagnosis-treatment processes by comprehensively examining the relationship of mental contamination with childhood traumas, clinical features and alexithymia, a dimension not previously addressed in the literature, in individuals diagnosed with OCD.

The study included 70 patients diagnosed with OCD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, who were admitted to the Department of Psychiatry at the Bursa Yüksek Ihtisas Training and Research Hospital between August 2023 and August 2024, and 70 healthy volunteers who had not been diagnosed with a psychiatric disorder in the past or currently. The data from the first 30 participants were used to determine the number of subjects to be included in the study. The relationships between Vancouver Obsessional Compulsive Inventory-Mental Contamination Scale (VOCI-MC), Childhood Trauma Questionnaire (CTQ, r=0.331) and Toronto Alexithymia Scale (TAS, r=0.364) were examined. Based on the results obtained, the number of participants to be included in the study was calculated when the lowest correlation coefficient was taken as 0.331. In this study, when α=0.05, β=0.20, and r=0.331 were taken, it was concluded that the number of participants to be included in a group should be at least 69 (N=[(Zα+Zβ)/C]2+3=69 [11].

Participants in the OCD were selected using consecutive sampling from patients aged 18-65 years who were followed up at our clinic, diagnosed with OCD based on a clinical interview conducted by a psychiatrist in accordance with DSM-5 diagnostic criteria. Patients with additional psychiatric comorbidities were excluded based on clinical interview and review of clinical records. Participants in the control group (CG) were determined on a voluntary basis and declared that they had not received any psychiatric diagnosis in the past or currently before participating in the study. These declarations were supported by a brief preliminary interview conducted by the researcher.

In selecting the CG, care was taken to include individuals with similar age, gender, and education levels to the OCD.

Participants were administered a sociodemographic data form designed by the researcher, which inquired social data such as age, gender, educational status, marital status and clinical data such as age and duration of onset of illness, number of hospitalizations, medication use, alcohol-substance use and presence of physical illness.

In order to measure the type and severity of obsessive-compulsive symptoms, “Yale-Brown Obsession Compulsion Scale (Y-BOCS)” and “Yale Brown Symptom Check List” developed by Goodman et al. [12] were used. The Y-BOCS includes questions evaluating the severity of obsessions and compulsions, the degree of discomfort they cause to the person, the level of insight into the disease and the general course of the disease. It consists of 19 items in total, but only the first 10 items are used to calculate the total score. The score of each question varies between 0-4. The scale is administered by the interviewer. The items of insight, avoidance, ambivalence, pathological responsibility, slowing down and pathological doubt are scored between 1-4, but are not included in the total score. In addition, the scale is accompanied by a symptom checklist to investigate symptom distribution. The Turkish adaptation’s validity and reliability were evaluated in a study conducted by Karamustafalıoğlu et al. [13].

The VOCI-MC developed by Rachman [14] was used to assess the severity of mental contamination symptoms in individuals. The scale is a 5-point Likert-type scale with 20 items. High scores obtained from the scale indicate an increase in the participant’s tendency to feel mental contamination. The adaptation of the scale into our language was conducted by Inozu et al. [15].

In order to measure childhood traumas, the CTQ, which is an easy-to-administer quantitative measurement tool that is useful in retrospectively evaluating abuse and neglect experiences before the age of 20, has been shown to be valid and reliable, and is based on the individual providing information, was used. It was developed by Bernstein et al. [16]. While the first version of the scale had 53 items, the current version has 28 items. The CTQ scale was adapted into Turkish by Sar et al. [17] in 2012.

The TAS, a 20-item, 5-point Likert-type, 3-factor measurement tool developed by Bagby et al. [18] and adapted into Turkish by Güleç et al. [19], was used to determine alexithymic characteristics. These factors are difficulty in recognizing emotions, extroverted thinking and difficulty in verbalizing emotions.

The mean age of the OCD was 31.51±11.74 and the mean age of the CG was 33.20±10.83. According to the Independent groups test, the groups were statistically similar in terms of age (t=-0.88, p=0.379). In the OCD, 57.1% (n=40) of the participants were female, 42.9% (n=30) were male; 51.4% (n=36) were married, 48.6% (n=34) were single, and their educational levels were primary school 10.0% (n=7), secondary school 37.1% (n=26), high school 12.9% (n=9), university 40.0% (n=28). In the CG, 57.1% (n=40) of the participants were female, 42.9% (n=30) were male; 50.0% (n=35) were married, 50.0% (n=35) were single, and their education levels were middle school 38.6% (n=27), high school 12.9% (n=9), university 48.6% (n=34). According to the chi-square test, the rates of gender, education (χ2=7.60, p=0.055) and marital status (χ2=0.03, p=0.866) were similar between OCD and CG. In the CG, 7.1% (n=5) of the participants had a history of physical illness, whereas in the OCD, 17.1% (n=12) had a history of physical illness and 2.9% (n=2) had a history of psychiatric hospitalization. In the OCD, 78.6% (n=55) were receiving regular psychopharmacologic treatment. According to the chi-square test, the rates of physical illness were similar between OCD and CG (χ2=3.28, p=0.070). The mean duration of illness of OCD cases was 8.88±7.79 (min.=1.00-max.=34.00), the mean Y-BOCS-obsessions (OB) was 11.19±4.45 (min.=0.00-max.=20.00) and the mean Y-BOCS-compulsions (COM) was 9.81±5.00 (min.=0.00-max.=20.00) (Table 1).

When the obsession types of individuals diagnosed with OCD were analyzed; 52 (74.3%) had contamination obsessions, 42 (60.0%) had other obsessions, 38 (54.3%) had religious obsessions, 28 (40.0%) had aggression obsessions, 22 (31.4%) had sexual obsessions, symmetry-order obsession in 19 (27.1%), accumulation and storage obsession in 3 (4.3%) and somatic obsession in 1 (1.4%). When the types of compulsions were evaluated; 44 (62.9%) patients had cleaning-washing, 44 (62.9%) patients had other compulsions, 42 (60.0%) patients had repetitive ritualistic behaviors, 37 (52.9%) patients had controlling, 26 (37.1%) patients had counting, 21 (30.0%) patients had sorting/organizing, and 4 (5.7%) patients had accumulating/collecting compulsions.

In the independent groups t-test, it was found that the mean VOCI-MC (t=6.369, p<0.001), CTQ (t=2.635, p=0.009), and TAS (t=3.835, p<0.001) scores of the OCD cases were statistically significantly higher than the mean scores of the participants in the CG (Table 2).

According to pearson correlation analysis results, significant positive correlations were found between Y-BOCS-OB scores and Y-BOCS-COM (r=0.785, p<0.001), VOCI-MC (r=0.238, p=0.047), CTQ (r=0.383, p=0.001), and TAS (r=0.425, p<0.001) scores (Table 3). Significant positive correlations were found between Y-BOCS-COM scores and VOCI-MC (r=0.260, p=0.030), CTQ (r=0.326, p=0.006), and TAS (r=0.350, p=0.003). In addition, there were significant and positive correlations between VOCI-MC and CTQ (r=0.388, p=0.001) and TAS (r=0.469, p<0.001) and between CTQ and TAS (r=0.537, p<0.001).

According to the results of pearson correlation analysis in the CG group, a significant and positive correlation was found between VOCI-MC and TAS (r=0.518, p<0.001). There is also a positive and significant correlation between CTQ and TAS (r=0.374, p=0.001). In addition, no significant correlation was found between VOCI-MC and CTQ (r=0.201, p=0.096).

For the total of 10 pairwise correlation comparisons among five variables (Holm number m=10), the Holm-Bonferroni correction was applied to control the risk of Type I error associated with multiple comparisons (α=0.05). After the Holm correction, the correlations between VOCI-MC and Y-BOCS-OB (p=0.047) and Y-BOCS-COM (p=0.030) scores lost their statistical significance, while all other relationships retained their significance.

In regression analysis, tolerance and variance inflation factor (VIF) values were examined to assess multicollinearity among independent variables. Tolerance values range from 0.354 to 1.000. Their values being above the generally accepted threshold (≥0.20) indicate that there is no excessive multicollinearity among the independent variables. VIF values ranged from 1.000 to 2.825. These values are well below the commonly accepted threshold values (VIF <5; maximum limit <10). This indicates that the independent variables can be reliably included in the regression model and do not cause multicollinearity issues.

In the hierarchical regression analysis, when Y-BOCS-OB and Y-BOCS-COM variables were included in Model 1, the model was not significant (R²=0.07, F=2.55, p=0.086). When the CTQ variable was added to the Y-BOCS variables in Model 2, the model became significant (R²=0.17, F=4.53, p=0.006). In this model, only the CTQ variable significantly predicted the VOCI-MC scores (B=0.489, β=0.342, p=0.006, 95% confidence interval [CI]=0.143 to 0.836). In Model 3, the variance explained increased to 26% with the addition of the TAS variable (R²=0.26, F=5.60, p=0.001). In this model, the effectiveness of CTQ (B=0.263, β=0.184, p=0.161, 95% CI=-0.107 to 0.633) in explaining the VOCI-MC scores was lost, and only TAS scores (B=0.503, β=0.362, p=0.008, 95% CI=0.136 to 0.870) significantly predicted VOCI-MC scores. In the OCD, adding the number of contamination obsessions and the presence of cleaning compulsions to the model increased the model’s explanatory power to 39% (F=6.73, p<0.001). In addition, TAS was the only variable that significantly explained VOCI-MC scores (p=0.010). Therefore, alexithymic traits were found to be the only variable with a statistically significant effect (Table 4).

According to the results of the hierarchical regression analysis in the CG, when only the CTQ variable was included in Model 4, the model was not statistically significant (R²=0.04, F=2.86, p=0.096). In Model 5, the model became significant with the addition of the TAS variable (R²=0.27, F=12.29, p<0.001). In this model, only the TAS variable significantly predicted VOCI-MC scores (B=0.383, β=0.515, p<0.001, 95% CI=0.216 to 0.550).

In our study, mental contamination in OCD was examined in detail together with clinical variables, childhood trauma and alexithymia variables. OCD and CGs were matched sociodemographically and no significant difference was found between the groups in terms of gender, age, marital status, educational level, and presence of physical illness. This supports the methodological soundness of our study and the validity of the results obtained.

In our study, mental contamination, childhood trauma and alexithymia scores were significantly higher in OCD patients compared to healthy volunteers, and there were significant positive correlations between obsession-compulsion scores and mental contamination, childhood trauma and alexithymia scores.

In recent research, mental contamination is defined as a transdiagnostic construct that, while particularly associated with OCD, can also be observed in other psychopathologies and even in non-clinical populations [2,4]. On the other hand, it has been shown that mental contamination can be seen in nearly half of OCD patients and may be effective in understanding and intervening in this disorder [3,5]. Some studies show that mental contamination is a separate but conceptually overlapping structure with classical OCD symptoms such as contact contamination [21]. On the other hand, in addition to obsessions about contamination, mental contamination is also related to other obsessive-compulsive symptom dimensions and different psychological processes such as immorality, disgust and shame [5,22].

The Holm-Bonferroni correction was applied to correlation analyses to control the risk of Type I error associated with multiple comparisons. After adjustment, the statistical significance of the relationships between mental contamination and Y-BOCS-OB and Y-BOCS-COM scores was lost, whereas the significance of the relationships between mental contamination and childhood traumas and alexithymia was preserved. This finding suggests that mental contamination in OCD patients may be more closely related to difficulties in recognizing and expressing early life experiences and emotions than to the severity of OCD symptoms.

Therefore, it may be appropriate to evaluate mental contamination not only within the context of OCD symptomatology but also from a broader perspective that includes psychosocial and developmental factors. Given that these factors are important in many psychopathologies and even in healthy individuals, the view that mental contamination is a transdiagnostic component is supported. However, due to the nature of our study, these relationships should not be interpreted in terms of causality.

Recent reviews show that childhood traumas are common in OCD patients and contribute to the severity, symptom characteristics and treatment resistance of OCD [6,23]. In this respect, the fact that childhood trauma scores were significantly higher in the OCD than in the CG in our study and that this was positively correlated with obsession-compulsion scores is consistent with the literature. In addition, a significant positive correlation was found between mental contamination and childhood trauma in OCD patients in our study. In recent years, it has been debated that mental contamination may explain the relationship between childhood traumas and OCD [7]. It is thought that mental contamination may develop when traumatic experiences that trigger feelings of disgust are internalized or perceived as guilt-shameful situations [7]. These individuals may resort to different coping patterns such as avoidance, mental neutralization, or safety behaviors in addition to cleaning and washing behaviors. The literature shows that OCD patients with a history of traumatic experiences have lower treatment success rates [24]. A history of trauma may complicate compliance with interventions such as exposure therapy in OCD treatment. In cases where mental contamination is present, structuring interventions targeting these cognitive-emotional themes may pose clinical challenges [7]. In clinical practice, it may be beneficial to assess OCD patients for past trauma history and mental contamination. For clearer inferences, studies with a design in which advanced structural models can be used are needed. The lack of a significant relationship between mental contamination and childhood trauma in the CG can be explained in the context of the stress-diathesis model: stressors such as childhood trauma may trigger cognitive/emotional responses such as mental contamination only in individuals with certain psychopathological tendencies, as in OCD. In healthy individuals, similar experiences may not translate into symptoms of mental contamination. In addition, the content of the traumatic experience may also influence this process. For this reason, it may be useful to conduct studies in larger populations and to investigate the content of traumatic experiences.

Alexithymia is a personality trait characterized by difficulty in recognizing and expressing emotions and extroverted thinking style and can be seen both in the general population and in many psychiatric disorders including OCD. Studies have shown that alexithymia is an important factor in OCD symptom content, severity and suicide risk [9,25,26]. In a recent meta-analysis by Kick et al. [27], alexithymia was shown to have a significant positive association with all types of child abuse and general psychopathology, and to partially mediate the relationship between childhood abuse experiences and general psychopathology in adulthood. It has been shown that alexithymia is common in individuals with PTSD and is associated with some prominent clinical symptoms such as re-experiencing, hyperarousal, depersonalization, dissociation and a history of childhood emotional neglect [28]. In addition, in a group diagnosed with PTSD related to motor vehicle accidents, significant relationships were found between the severity of alexithymia and the functional activation of some brain regions during trauma description [27]. Although there is an established association between OCD and childhood trauma, studies suggest that this relationship is not direct but is mediated by difficulties in emotional processing [8]. Considering that alexithymia is one of the indicators of these emotional processing difficulties; in our study, higher alexithymia scores in OCD patients, a significant positive correlation between OCD symptom severity and alexithymia, and a significant correlation between childhood trauma scores and alexithymia in both control and patient groups are consistent with the literature.

Our study found a significant positive relationship between mental contamination and alexithymia in OCD patients. While the severity of obsessions and compulsions did not directly predict mental contamination, a positive relationship was observed between childhood traumas and mental contamination, and the trauma variable was a significant predictor in hierarchical regression analysis. However, when alexithymia was added to the model, the predictive effect of trauma disappeared, and alexithymia was found to be the variable that maintained a significant relationship with mental contamination within the regression model.

Although the explanatory power of the model increased when contamination obsessions and cleaning compulsions were included in the model, the variable that maintained a significant relationship with mental contamination scores even when these symptom dimensions were statistically controlled was alexithymia. This finding suggests that mental contamination may not merely be a reflection of contamination/washing symptoms and may be related to a broader cognitive-emotional process. However, due to the cross-sectional design of the study, these relationships cannot be interpreted causally.

To our knowledge, this study is the first to examine the relationship between alexithymia and mental contamination in OCD patients. Even when disease severity, contamination/infection obsessions, cleaning compulsions, and childhood traumas were evaluated together, alexithymia emerged as one of the variables most consistently associated with mental contamination.

In a study conducted with university students, it was found that mental contamination showed a positive significant relationship with feelings of anger and disgust [15]. Since alexithymic individuals have difficulty in recognizing and expressing emotions, they may have difficulty in coping with complicated emotions such as disgust, shame, guilt, anger, which can be seen frequently in OCD. This situation may contribute to the expression of difficult-to-define and suppressed emotions in the form of mental contamination, which is a more abstract and internal concept. For this reason, it may be useful in clinical practice to also evaluate OCD patients in terms of alexithymia.

In healthy individuals, trauma had no effect on mental contamination and alexithymia stood out as an independent predictor. This finding suggests that mental contamination in healthy individuals is more related to personal emotional awareness and regulation skills rather than traumatic experiences. In other words, even if healthy individuals have traumatic experiences, this situation is not directly reflected on mental contamination; mental contamination is shaped more by the individual’s capacity to identify, understand and express their emotions. When both groups are evaluated together, it can be said that alexithymia may be a common risk factor and potential area of intervention in terms of mental contamination.

This study demonstrates that mental contamination is a concept that, while more frequently observed in OCD, can also be seen in the general population. Our findings indicate that in OCD patients, early traumatic experiences and emotional processing processes, rather than OCD symptoms, play a role in the formation of mental contamination; specifically, alexithymia appears to have a prominent role and warrants further investigation. Therefore, we recommend a more detailed assessment of mental contamination and alexithymia in OCD patients. In healthy individuals, protective measures aimed at developing the ability to recognize and express emotions may prevent the development of maladaptive cognitive themes similar to mental contamination.

Although the findings of our study provide important contributions to the field, it has some limitations. Due to the cross-sectional design of our study, a cause-effect relationship cannot be established in the relationships between variables. The diagnostic assessment was not supported by structured clinical interview tools such as the Structured Clinical Interview for DSM Disorders; instead, the diagnostic process was conducted based on clinical interviews. This may have limited the detailed and standardized exclusion of comorbid psychiatric disorders or subthreshold psychiatric symptoms in the CG. Additionally, since potentially confounding variables such as depression and anxiety symptoms were not fully controlled, the specificity of the prominent relationship between alexithymia and mental contamination may be limited. The fact that the data of the individuals in the OCD regarding their being under treatment and the treatment process could not be controlled and the use of self-report scales can be considered as a limitation. The retrospective assessment of childhood traumas may have increased the risk of recall bias. Additionally, the fact that the variables were evaluated at the same time point and through self-report scales raises the possibility that the relationships between variables may have been affected by common method variance. The sample size and the selection of participants from a specific region may limit the generalizability of the findings.

In the future, we think that longitudinal studies conducted with larger and diversified samples in which structured clinical assessments are applied, obsession-compulsion symptom profiles contents and subtypes of childhood traumas can also be analyzed will contribute to the field. In addition, testing the effect of alexithymia on mental contamination, which emerged prominently in our study, in studies where depressive and anxiety symptoms are included in statistical models as potential confounding variables, and conducting mediation analyses, will contribute to a clearer understanding of the relationships between variables.