Obsessions in OCD as Intrusive Thoughts: Historical and Clinical Reflections

By Eva Surawy Stepney, PhD Candidate, and Jonathan Hoffman, PhD, ABPP

Editor's Note: This article reflects the opinions of its authors and does not necessarily represent the views of the IOCDF.

The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR) refers to OCD obsessions as “recurrent and persistent…intrusive and unwanted thoughts, images, and urges.” Our impression is that people with OCD and related disorders increasingly summarize their experience of obsessions as “intrusive thoughts.” This observation sparked our interest in reflecting on the history of how obsessions came to be described in this way, and whether this has proven to be a positive development from a clinical perspective.

A 20th Century History of ‘Intrusive Thoughts’

The concept of “intrusive” symptoms is rooted in early 20th-century ideas of war trauma. In Remembering, Repeating, and Working-Through (1914), written during the First World War, Sigmund Freud theorized that the repression of a traumatic event led a person to experience a persistent and forceful repetition of thoughts and images.1 The function of this “repetition compulsion” was to facilitate a conscious regaining of agency over passive events in the unconscious. In his discussion of “war neuroses,” the British psychiatrist W.H.R Rivers similarly referred to fearful thoughts and images being “thrust into manifest consciousness.”2 Rivers combined Freudian reasoning with the theories of neurologist John Hughlings Jackson to suggest that when faced with an extreme threat, higher-level functions in the nervous system became impaired and lower-level functions (fearful thoughts) “escaped from their restraining effects.”

The distinct symptom of “intrusive thoughts” came to prominence during the Vietnam War (1955-1976), when the psychiatrist Mardi Horowitz (University of California) was enlisted to explain why so many American soldiers experienced difficulties readjusting to civilian life. During his research, Horowitz observed that “intrusive repetitive thoughts” are found in people “who are struggling to master recent stressful events” and may be “a distinctly symptomatic response to stress.”3 In exploring this hypothesis, the psychiatrist conducted experiments on over 300 university students. They were shown two films — one that was “neutral” (non-stressful) and one of a woodshop accident and severe bodily injury — and asked to write down their thoughts and the intensity of any associated affect. From the results, Horowitz observed that witnessing stressful events led a “normal” person to experience “intrusive and stimulus-repetitive thoughts” and that “most people’s subjective experiences of intrusive thoughts increased” after exposure to a stressor.

Horowitz referred to this idea of “intrusive thoughts” as a “modernization of Freud’s repetition compulsion.” He drew on the information processing model of cognitive science to propose that stressful events imposed a strain on the mind’s “normal” mechanism of “processing” (information matching). In cases of high-stress “the working out of how new information is to be integrated with old information about the world will be hard or time consuming.” Depending on a person’s “threshold of tolerance” a stressful event would either be “processed” and stored in memory or get stuck in a cycle of “intrusive repetition.” Horowitz’s research led to the inclusion of “intrusive thoughts” as a key symptom of post-traumatic stress disorder (PTSD) in DSM-III.

The link between the “intrusive thoughts” of stress/trauma research and the “obsessions” of OCD began in 1978 when, due to obstacles in behavior therapy (ethical critique, lack of consistent cure rates), the British psychologist and key OCD researcher Stanley Rachman sought alternatives to the purely behavioral (stimulus-response) model of obsessions and compulsions. During a six-month fellowship to the University of California, where he was exposed to Horowitz’s research, Rachman noticed that “intrusive thoughts” shared many similarities with obsessions: both were experienced by the “normal” population, contained “stimulus-repetitive content,” and were “hard to dispel.”4 On returning back to the UK, Rachman adopted the idea of “intrusive thoughts” as a lens through which to further explore and add “conceptual clarity” to the definition of “obsessions.” Over time, however, the psychologist began merging the concepts, describing “obsessions” as “unwanted, intrusive cognitions” (and vice versa).

Since Horowitz identified intrusive thoughts as the result of stress, Rachman questioned whether stressful events — and failures to process them — also explained the origin of obsessions. Between 1980 and 1983, Rachman and his student Luke Parkinson conducted research exploring whether intrusive thoughts/obsessions were generated during periods of stress. In an experiment, 50 mothers — half of whose children were being admitted to hospital for surgery — were tasked to write down their intrusive thoughts on the day before, the day of, and the day after admission. Mothers whose children were admitted experienced “high stress levels,” reporting a greater number of “intrusive cognitions (such as obsessions)” than those in the control group.5

Rachman turned to the cognitive model of the mind as a “processor” to develop a “unifying concept for intrusive thoughts and obsessions” which he termed “emotional processing.”6 Building on his predecessors, he maintained that obsessions/intrusive thoughts could be the result of an emotional event which had not yet been appropriately stored in memory. Behavioral exposure techniques were rearticulated within this framework: exposure to stimuli “is a matter of breaking down the incoming stimulation into manageable proportions.” The presence of “intrusive obsessions” became a sign of incomplete processing.

By 1982, Rachman had more firmly conceptualized obsessions as “intrusive thoughts” which were “unwanted, unacceptable, persistent, cause distress, and the sufferer cannot get accustomed to.”7 As we turn toward discussing this auspicious development through a clinical lens, perhaps we may also wonder whether Rachman was unhelpfully inconsistent in defining “intrusive thoughts” as obsessions versus being experienced as obsessions. We must also ask if it made sense to generalize concepts about intrusive thoughts — originally gleaned from the research on trauma and stress we have described — to obsessions occurring in the context of OCD.

Clinical Reflections

Let’s now consider the clinical side of “intrusive thoughts” in the context of OCD today and what is gained or compromised by utilizing this term. On the plus side, and considering how use of the word “obsessed” in common language (as in, “I’m obsessed with this Netflix show”) has diluted its meaning, “intrusive thoughts” may better convey how bad, frightening, peculiar, doubt-creating, embarrassing/shameful such thoughts feel than the word “obsessions.” For clinicians, using this term may also be helpful in providing experiential validation, which can aid building rapport in the therapeutic process. Also, for all we know, the inner experience of thinking may be qualitatively different in OCD; perhaps certain thoughts feel “intrusive” because they are being conflated with external stimuli, such as sensory information. But this is just speculation.

On the minus side, when a clinician validates the subjective experience of a thought as “intrusive,” they suggest that a thought can actually be “intrusive” or that thoughts can be demarcated as “regular” and “intrusive.” All thoughts are intrusive by nature, as anyone that meditates well knows; sure, we can bring a certain thought to mind briefly, but that’s about it. Additionally, the very notion of “intrusive thoughts” would seem contrary to OCD basics, such as “a thought is just a thought” and connecting a thought with a behavior is magical thinking, thoughts are ultimately involuntary, and being on “thought patrol” to monitor and control thoughts is exhausting, futile, and predicted to backfire. An important point to make here is that it is how a person perceives and responds to a thought, rather than the thought itself or if it’s experienced as “intrusive,” that determines if it will become more intense, repetitive, and time-consuming, or trigger compulsive/avoidant behavior.

Another concern about “intrusive thoughts” is that it may make some people view their mind as a potential enemy within. Even if one accepts the premise of “intrusive thoughts,” determining what constitutes “intrusivity” would be impossible, since it is entirely subjective. Anecdotally, people with OCD even vary as to whether the same exact thought feels as intrusive (or intrusive at all) on any given day or moment.

Lastly, is the notion of being “intrusive” essential to defining obsessions? If the concept was removed, the unwelcome aspect of the obsessive thought would remain, but would that be enough? Perhaps it would. We noted earlier that it is our impression that talking about obsessions as “intrusive” (rather than unwanted) thoughts may be trending. But to us, given that no one can control their thoughts, the notion of labeling thoughts as “wanted” or “unwanted” makes as little sense as categorizing them as “regular” or “intrusive.” However, if we are stuck with such terms, at least “unwanted” makes a similar point as “intrusive,” but with less emotional valence. We believe it also sidesteps the unfortunate connotation that a thought — regardless of its subjective experience — can have an ultimate moral dimension such as “badness,” while providing a degree of agency for the thinker. Another positive is that it avoids the suggestion of a rampaging, traumatizing thought invading the mind against one’s will.

A counter-argument to some of the concerns we have raised is that the DSM-5-TR clearly states that obsessions are experienced as, rather than are, “intrusive.” However, again, we think this can be very easily lost in translation. Obviously, we have some misgivings about the concept of “intrusive thoughts” and believe that it tends to confuse rather than improve how obsessions are conceptualized clinically. But if definitions of obsessions in future DSMs and elsewhere will refer to “intrusive thoughts,” we wonder if more careful wording might be in order. Accordingly, we advocate for modifying present diagnostic language defining obsessions to make it crystal clear to all that obsessions are thoughts that are subject to “erroneously being experienced as intrusive.” Immediately, this might help reduce the sense of labeling thoughts as being inherently bad, weird, traumatizing, and capable of inducing guilt and shame. Adding “erroneously” to the definition of obsessions would also continue to allow for validating one’s subjective experience of “intrusive thoughts” in the broader context and benefit the psychoeducation process.

We hope this article reflecting on the historical origins and clinical aspects pertaining to   “intrusive thoughts” stimulates further discussion on how, when utilizing this term, to do so in as meaningful and helpful a way as possible, especially for clinicians and in our diagnostic manuals. We also hope it encourages readers to reflect on the bigger question raised of whether using this terminology at all to describe obsessions continues to be justified. Perhaps the less any definition of obsession deviates from the “recurrent and persistent” aspect, the better. Obsessions are a difficult enough clinical phenomenon to understand from a scientific standpoint without adding any further, if we may say, “intrusive” descriptors that risk further muddying the waters. More generally, we wish to stress the importance of understanding concepts that are presently used in our diagnostic and clinical reasoning from their origins, as well as reflect on their current theoretical and therapeutic validity, and treat none as if they are written in stone.


Eva Surawy Stepney is a PhD candidate in the Department of History at the University of Sheffield. Funded by the White Rose College of the Arts and Humanities (WRoCAH), her thesis explores the history of obsessive-compulsive disorder (OCD) and its intersection with post-war British clinical psychology. You can contact her by email at esurawystepney1@sheffield.ac.uk.

Jonathan Hoffman, PhD, ABPP, is Founder and Chief Clinical Officer at Neurobehavioral Institute (NBI), Founder at NBI Ranch, and a member of the IOCDF Scientific and Clinical Advisory Board. You can contact him by email at info@nbiweston.com.



1 Freud, S.(1914). Remembering, Repeating, and Working-Through. In Strachey, J. (Ed). (1950), Vol.XII of the Standard Edition of the Complete Psychological Works of Sigmund Freud, 147- 156.

2 Rivers, W.H.R. (1920). Instinct and the Unconscious: A Contribution to a Biological Theory of the Psycho-Neuroses, Cambridge: Cambridge University Press.

3 Horowitz, M. J. (1975). Intrusive and Repetitive Thoughts After Experimental Stress. Arch Gen Psychiatry, 32(11), 1457-1463. https://doi.org/10.1001/archpsyc.1975.01760290125015

4 Rachman, S. (1981). Part 1: Unwanted Intrusive Cognitions’. Advances in Behaviour Research and Therapy, 3(3), 89-99. https://doi.org/10.1016/0146-6402(81)90007-2

5 Rachman, S. & Parkinson L. (1981). ‘Part III: Intrusive Thoughts: The Effects of An Uncontrived Stress’, Advances in Behaviour Research and Therapy, 3(3), 111-118.

6 Rachman, S. (1980). ‘Emotional Processing’. Behaviour Research and Therapy, 18(1), 51-60. https://doi.org/10.1016/0005-7967(80)90069-8

7 Rachman, S., Sutherland, G., & Newman, B. (1982). ‘Experimental investigations of the relations between mood and intrusive unwanted cognitions’. British Journal of Medical Psychology, 55, 127-138. https://doi.org/10.1111/j.2044-8341.1982.tb01491.x