Mental contamination and obsessive disorder

The concept of mental contamination, initially studied in the context of the psychological consequences of sexual abuse (Fairbrother & Rachman, 2004), was rapidly extended to obsessive-compulsive disorder, in particular to the fear of contamination and the related washing/cleaning rituals, giving rise to an important line of research

What is meant by fear of mental contamination?

Rachman (2004) defined the fear of contamination as an intense and persistent feeling of being contaminated, infected or endangered by direct or indirect contact with a person, place or object perceived to be dirty, impure, infected or harmful.

Within the fear of contamination, two different types have subsequently been distinguished: the so-called physical contamination (or contact contamination), which we commonly refer to when talking about OCD, and mental contamination, which we will discuss in this article.

What are the differences?

Physical contamination implies an external sensation of dirtiness evoked by direct or indirect (or even just imagined) physical contact with a tangible, easily identifiable contaminating substance, person or object, such as germs, bacteria, toxic substances, body fluids (in particular, blood, faeces, semen and urine).

Mental contamination, on the other hand, is a sense of psychological contamination, involving an internal emotional feeling of ‘dirtiness’ without any physical contact whatsoever (triggered, for example, by particular thoughts, words, memories or images).

This feeling of dirtiness is not directly observable by others; it is referred to as something diffuse, hardly identifiable in one part of the body.

Individuals with mental contamination may report a need to wash themselves

They may also engage in complex mental and control rituals in order to reduce unpleasant emotions, although they generally never manage to feel totally ‘clean’ and in place.

Situations capable of triggering a state of mental contamination may involve both psychological (e.g. a betrayal that has made the person feel humiliated, shamed, manipulated, degraded) and physical violations (e.g. sexual violence), but also, on the other hand, the perpetration of despicable actions such as the above (resulting in moral self-loathing); then there are the episodes of so-called self-contamination, i.e. mental events, such as blasphemous, sexualised or violent thoughts (e.g. aggressive obsessions), that ‘contaminate’ the person’s mind. aggressive obsessions), which ‘contaminate’ the person morally, so unworthy and unacceptable are they.

Lady Macbeth effect

The best known example, also because it is literary, of mental contamination is represented by Lady Macbeth.

In Shakespeare’s famous tragedy, Lady Macbeth, accomplice to the murder of King Duncan of Scotland and other misdeeds, desperately tries to wash away the imaginary blood stain by incessantly washing her hands.

She realises with deep dismay that, although her hand no longer contains any trace of blood, nothing can ever erase the smell, which she still feels on her hands as an indelible mark of her deed.

What Shakespeare describes in the tragedy of Macbeth has found experimental confirmation in a study conducted in 2006 by Zhong and Liljenquist, in which the authors demonstrated an association between physical cleanliness and moral cleanliness: exposure to immoral events stimulates a threat to one’s moral integrity by inducing the need to wash oneself (cleanse oneself), even though there is no real external dirt and washing only has a symbolic ‘purifying’ function.

From the results of some studies, it appears that physical cleansing can restore moral purity, without the need to engage in compensatory behaviour (such as, for example, an altruistic gesture of providing help to another).

Mental contamination: an important ingredient of obsessive compulsive disorder

A study of ours, recently published in the Journal of Obsessive-Compulsive and Related Disorders (Melli, Carraresi, Stopani, & Bulli, 2014), set out to investigate the prevalence of mental contamination in a sample of patients with obsessive-compulsive disorder (OCD) by contamination and to analyse the mediating role of mental contamination in the relationship between the trait tendency to feel disgust and obsessive symptomatology.

Of the 63 OCD patients in our sample, over 60% reported the presence of mental contamination.

Our results also confirmed the hypothesis that mental contamination partially mediates the relationship between disgust tendency and obsessive symptoms.

In other words, OCD subjects with a higher tendency to feel disgust when they experience events that make them feel mentally contaminated (e.g., physical or psychological violation, immoral thoughts, morally unacceptable images or impulses), may feel very dirty and disgusted and resort to maladaptive behaviour (e.g., washing compulsions) that keeps the obsessive symptomatology active.

It thus appears from our study that mental contamination plays a significant role in OCD subjects with a fear of contamination, particularly as a mediator of the relationship between propensity to disgust and contamination thoughts/behaviours.

This result may confirm what has been emphasised in the literature regarding the importance of an accurate assessment of critical events precipitating the onset of OCD with fear of contamination.

Mental contamination, as mentioned above, seems to emerge as a consequence of ‘polluting’ life events

In them the person has felt morally wronged (as a result of actions committed) or violated, humiliated (as a result of actions suffered).

What implications for the treatment of obsessive-compulsive disorder?

Given the ‘traumatic’ nature of the state of mental contamination, it is worth reflecting on the extent to which emotions of guilt and disgust in relation to certain stimuli on the part of OCD subjects represent a kind of affect without recollection (Clark, 1999).

In other words, certain situations could activate the emotional experience related to traumatic memory, even if the patient confines himself to the contingent problem that triggers the fear of contamination at that moment.

It might be interesting to consider whether all that the obsessive patient feels compelled to do in order to avert a situation in which he may feel guilty (or disgusted) represents a coping modality with respect to a negative self-assessment, as encoded in that critical event, precipitating the onset of the disorder.

In this regard, the purpose of obsessive activity could be to repair a profoundly ‘polluted’ idea of self, as it was activated at the time of the event precipitating the disorder, or to avoid actions that could reactivate that same negative idea of the person, making him or her feel disgusted, humiliated and potentially a source of contempt from the community to which they belong.

The fact that mental contamination is linked to a negative self-assessment as a consequence of critical events triggers reflection on how much this internal feeling of dirtiness is linked to a problem of non-processing/integration into the autobiographical memory of the past critical event(s) and how DOC subjects with mental contamination, through washing and other neutralising behaviours, try to distance themselves from the thoughts and feelings connected to the memory (‘wash away the past’).

Understanding the role of mental contamination in mental contamination OCD allows the development of potentially more effective treatments.

Here, the possibility of supplementing Exposure and Response Prevention – which we know to be the proven effective treatment in OCD – with work on reprocessing traumatic events, using techniques such as imagery rescripting or EMDR, could increase the success rate of standard cognitive-behavioural intervention.


Clark, D. (1999). Anxiety disorders: why they persist and how to treat them. Behaviour Research and Therapy, 37, S5-S27.

Fairbrother, N., & Rachman, S. J. (2004). Feelings of mental pollution subsequent to sexual assault. Behaviour Research and Therapy, 42, 173-190.

Melli, G., Carraresi, C., Stopani, E., & Bulli, F. (2014). Propensione al disgusto e sintomi del disturbo ossessivo compulsivo legati alla contaminazione: il ruolo mediatore della contaminazione mentale. Journal of Obsessive-Compulsive and Related Disorders, 3, 77-82.

Rachman, S. J. (2004). La paura della contaminazione. Ricerca e terapia del comportamento, 42, 1227-1255.

Zhong, C e Liljenquist, K. (2006). Lavare i propri peccati: Moralità minacciata e pulizia fisica. Science, 313, 1451-1452.

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