1. Introduction
uch research has revealed that disgust is closely related to psychopathology [1]. Among psychiatry disorders, disgust has an important role in the genesis and maintenance of contamination-based OCD [2, 3, 4, 5, 6]. The relation between disgust and contamination OCD rises this question that how and with which mechanism, disgust can result in contamination OCD symptoms. According to Cisler et al [11]. Although disgust can explain the avoidance of direct contaminants in people with OCD, it is not enough for explaining the avoidance of indirect contaminants in OCD, and the role of cognitive variables should be implicated. 
The most related cognitive distortions with disgust is the “sympathetic magic laws” [10], known more as the “law of contagion” [12, 13, 14, 15, 16]. This law states that people intend to behave as if a brief contact can lead to the permanent and full transmission of characteristics or the “essence” from one object to the other one [12]. Woody and Tolin [17] suggested that this law is more elevated in OCD washers and analog samples. The exaggerated perception of magical contagion in OCD people, in turn, causes overestimations of threats including general danger, becoming contaminated, and getting ill. Verwoerd et al. [20] suggested that people with higher fear of contamination overestimated the likelihood of becoming ill more than the normal control group even in conditions with no objective threats but with disgust response.
Thus, in this study, the proposed structural model examined through SEM procedure, displayed that the activation of disgust can lead to the motivation of the law of contagion and that in turn causes motivation of threat overestimations, which finally result in contamination OCD symptoms.
2. Methods
This is a correlational research design. Participants were 495 (59% women) students from Olum Tahghighat University which recruited through convenience sampling. The age range was 18 to 35 years old (Means±SD: 20.45±2.52). Most of them ranged from 18 to 20 (64%). 
Procedure
Students who were not busy in the time between classes were asked to participate in the research if they wished and completed all the questionnaires in the same order including threat estimations’ scenarios, The Vancouver Obsessional Compulsive Inventory contamination subscale (VOCI-C), Negative Spiritual Contagion subscale from Contagion Sensitivity Scale (CSS), and Core Disgust subscale from Disgust Scale (DS-R). 
Analytic strategies
The Means±SD and Pearson correlations as descriptive indicators were calculated. The structural model includes the relation between latent core disgust variable (its indicators were the subscale items) with latent fear of contamination variable (its indicators were obsessions and washing rituals) which was mediated by latent negative spiritual contagion variable (its indicators were the subscale items) and latent threat estimations variable (its indicators were the probability of danger, probability of becoming contaminated, and the probability of becoming ill). The model fit was examined through Structural Equation Modeling (SEM) procedures by the software of AMOS v. 18 while the following indices were reported: χ2, CMIN/DF, GFI, CFI, AGFI, RMSEA.
3. Results
In Table 1 the Means±SD and Pearson correlations were displayed for the variables in this study.



The structural model was also shown in Figure 1 and the fit indices were as follows: χ2=487.2, CMIN/DF=1.98, GFI=0.925, AGFI=0.91, CFI=0.934, and RMSEA=0.045. 
 

As CMIN/DF should be below 3, CFI, GFI and AGFI should be more than 0.90 and RMSEA should be below 0.06 [28, 29]. The model has a good fit especially based on CMIN/DF which is below 2 and RMSEA which is below 0.05. 
4. Discussion
The results revealed that the proposed structural model (Figure 1) has a good fit from which can be concluded that the magical law of contagion and threat estimations mediate the relation between core disgust and fear of contamination.
As mentioned before, to explain people’s fear of indirect contaminants in OCD, cognitive variables should be considered [11، 30]. Tolin et al. [15] found that OCD people’s avoidance of objects such as door handles can be explained by the perception of a “chain of contagion” in these patients, which means that they can detect the contamination track to further points from the original source, without decreasing in the original amount of contamination. 
In another research Zanjani et al. [31] found that a related concept to the law of contagion means looming vulnerability to contamination mediated the relation between disgust and fear of contamination which showed that people with OCD perceived contaminated stimuli not as fixed but as spreadable, approaching to them and in a way that the threatening force of them is increasing. In the same way, in the present study, the mediation role of the law of contagion showed that people with contamination-based OCD believed that through a brief contact a considerable amount of contamination or the “essence” can transmit from a contaminated object to the neural one and this essence remains for a long time. 
In the law of contagion, the transmission of pollution is not like a layer that can cover a surface of something but it is the essence transmission that may cause the nature of something to get changed. It is obvious that if one perceived that the essence of something has changed, even repeated washing cannot convert it, so this can explain the overestimations of threat and frequent washing in people with OCD. This overestimation of threat is consistent with Cisler et al. [32] that showed an overestimation of danger from obsessional beliefs can moderate the relation between disgust and fear of contamination. Another part of negative spiritual contagion things are related to the other function of disgust means protection of the psychological body [9].
Our results showed that people with the fear of contamination attempt to protect themselves from the transmission of immoral, behavioral or ominous characteristics. This concept of moral or spiritual contamination as Fedotova [23] has mentioned, is different from Rachman’s mental pollution [34]. The role of the law of contagion in OCD which cannot be explained by logical accounts is consistent with the previous research showed the role of magical thinking in OCD such as Thought-action Fusion beliefs [35] and magical ideation [36]. Finally, as researchers suggested, the law of contagion is intuition or heuristic [38], which its mediational role may have important implications in OCD treatment.
Ethical Considerations
Compliance with ethical guidelines
After explaining the study Objectives to the participants and assuring them of the confidentiality of their information and being free to leave the study at any time, an informed consent was obtained from them. This study has an ethical approval.
Funding
This study was extracted from the PhD. thesis of first author approved by the Department of Clinical Psychology at Shahed University. 
Authors contributions
Conceptualization, writing, editing & review: Mona Moradi Motlagh, Mohammadreza Nainian, and Ladan Fata; Methodology and software: Mohammad Gholami and Mona Moradi Motlagh; Data curation: Mona Moradi Motlagh and Gholamhosein Ghaedi.
Conflicts of interest
The authors declare no conflict of interest.



References