What is OCD?

OCD stands for obsessive-compulsive disorder. People with OCD are plagued by obsessions (negative thoughts, images, or impulses). They perform compulsions to reduce the distress caused by obsessions.

The purpose of this post is to give a brief overview of OCD and it’s components: obsessions and compulsions. While every patient has a unique history and display of symptoms, there are characteristics that distinguish OCD from other mental health problems. Let’s have a look at a case taken from the web 1.

Case example

”C.D., a 27-year old woman, complained of excessive checking. Her symptoms dated back to her childhood when she spent hours on homework because of a need to have each page perfect with no erasures or cross outs and hours arranging her room so that it was in perfect order before sleeping.

By high school she couldn’t complete assignments until after the term had ended and did not participate in any extra curricular activities because her time was spent checking work assignments. When C.D. entered college she developed new checking rituals to assure herself that she had not caused harm to anyone around her (e.g., checking electrical appliances for fear that she had started a fire, faucets for fear that she had left them running, and door locks for fear that she had left them open). These rituals began to consume several hours a day leading her to be late for class or to miss it entirely. 

Although she sought therapy, she did not tell the therapist about her obsessions and rituals for fear she would be labeled “crazy.” Her bedtime rituals grew to three to four hours, leaving her practically no time to sleep or study. Her appetite and mood plummeted and she stopped attending class. She left college and returned home…”

The case of C.D. is typical in several ways. Her symptoms had a gradual onset, became worse over time, and her symptoms changed over time rather than going away. Key concepts in OCD are obsessions and compulsions, the O and C. People with OCD usually have both obsessions and compulsions but they may also occur separately.


Obsessions are distressing thoughts, impulses, urges, doubts, or images that are inappropriate and intrusive. They are frequent and cause feelings of distress, anxiety, or disgust. The patient tries to suppress or ignore the obsessions, or to neutralise them with a different thought or behaviour.

There are several dimensions or themes of obsessions listed below. I have emphasised those that are relevant to the case of C.D.

  • Symmetry
  • Harm
  • Contamination
  • Forbidden or taboo thoughts (aggressive, sexual, and religious obsessions)

Most people experience distressing thoughts or impulses 23, but not everyone develops OCD. For example, I sometimes get the impulse to move closer to the edge of the platform when I am waiting for a train. Parents have intrusive thoughts about harming their children, especially when they haven’t slept for weeks! Why do these intrusive thoughts or impulses become obsessions for some?

Catastrophic interpretations

Some researchers point to the finding that people with OCD make catastrophic interpretations about their intrusive thoughts 4. If I think that my impulse to approach the edge of the platform means that I actually want to hurt myself, it is more likely that I will start obsessing about that impulse. The parent with an intrusive thought about harming their child might ascribe the thought to a lack of sleep. If instead he/she thinks it means that they are not fit as a parent and not a safe person to be around in general, the risk of developing an obsession about harming others is increased.

An inflated sense of responsibility

Another observation is that people with OCD might feel the need to control their thoughts more than others do, because they feel responsible for preventing harm to themselves and others 5. A recent review of OCD6 included this passage:

”… people who develop the disorder seem to misinterpret the significance and consequences of these thoughts, which leads them to engage in compulsions…”


When we feel anxiety, distress, or disgust, we want to remove that discomfort in some way. Anything that successfully reduces the discomfort caused by obsessions or prevents a feared consequence of happening will be more likely to happen in the future. Common strategies are to neutralise the obsession with some action or thought, or to avoid the situation, person, or object that triggers obsessive thoughts.

For people with OCD, the efforts to reduce discomfort and prevent harm become ritualised and excessive over time and develop into compulsions.

Compulsions are the ritualised and excessive efforts to reduce distress and prevent perceived harm from obsessions

Compulsions can take several forms (C.D. displayed checking and ordering): - Checking
- Ordering
- Washing
- Mental rituals

Compulsions often have a gradual start. When C.D. started to check her homework, it probably just lasted a few minutes and then gradually consumed more and more time because checking reduced her distress about having made a mistake. Another person may develop a habit of always checking electric appliances before leaving the apartment, which might develop into a time-consuming compulsion only after several years of gradual increase.

While the compulsion itself is usually voluntary, people with OCD will often feel that they have lost control of their behaviour and that they are unable to stop it on their own. This is because compulsions - at least in the beginning - serve to provide a quick relief from anxiety and distress. If you think you might have left the stove on when you left for work, going back to check will reduce your anxiety. This association between distress reduction and behaviour becomes so strong over time that the individual will have a hard time reducing the behaviour on their own.

Mental compulsions

Excessive checking or ritualistic hand-washing is often associated with OCD. Mental compulsions are a lesser known but important part of the disorder. Many obsessions are accompanied by both observable compulsions and unnoticed mental compulsions.

The parent with an intrusive thought about harming their child might reduce their distress by removing sharp objects from the house and thinking about how much they love their child. To reduce my distress at the train platform, I could start telling myself about all the times I have had this impulse without doing anything, or try to think about something else to distract myself.

Obsessions and compulsions in a negative cycle

Compulsions are performed with the goal of reducing distress caused by obsessions and to prevent any perceived harmful consequences. They persist when the distress reduction is quick and when the unwanted thought is suppressed.

The negative part is that the individual never learns that their appraisals are unrealistic (thinking about harming your child does not make you harm your child). Compulsions also trigger obsessions by acting as reminders of them. Finally, the absence of the feared consequence after performing a compulsion strengthens the belief of personal responsibility. In the model below, notice how an arrow on the right side goes back from efforts to remove obsessional fear to misinterpret as important or threatening, which symbolises this negative cycle.


The purpose of this post has been to show the characteristics of OCD. We have seen that obsessions arise from intrusive thoughts that are very common. What matters is not that we have these thoughts (everyone does), but what the thoughts mean to us. Making a catastrophic interpretation or having an inflated sense of responsibility are possible psychological mechanisms that explain why some people develop obsessions.

Compulsions are what a person does in an effort to reduce the discomfort or prevent the perceived danger from obsessions. They might be observable by others or occur inside one’s head. Compulsions develop gradually over time to become excessive and ritualised.

The time-consuming nature of both obsessions and compulsions makes OCD a devastating disorder. As with most mental disorders, the demand for effective treatments is higher than the supply. In future posts I will discuss the treatments that are available and some ideas on how we can increase access to effective treatments for OCD.


  1. http://columbiapsychiatry.org/ocd/case-examples ^
  2. Rachman, S., & de Silva, P. (1978). Abnormal and normal obsessions. Behaviour Research and Therapy, 16(4), 233–248. https://doi.org/10.1016/0005-7967(78)90022-0 ^
  3. Gibbs, N. A. (1996). Nonclinical populations in research on obsessive-compulsive disorder: A critical review. Clinical Psychology Review, 16(8), 729–773. https://doi.org/10.1016/S0272-7358(96)00043-8 ^
  4. Rachman, S. (1997). A cognitive theory of obsessions. Behaviour Research and Therapy, 35(9), 793–802. https://doi.org/10.1016/S0005-7967(97)00040-5 ^
  5. Salkovskis, P. M. (1985). Obsessional-compulsive problems: A cognitive-behavioural analysis. Behaviour Research and Therapy, 23(5), 571–583. https://doi.org/10.1016/0005-7967(85)90105-6 ^
  6. Hezel, D. M., & McNally, R. J. (2016). A Theoretical review of cognitive biases and deficits in obsessive–compulsive disorder. Biological Psychology, 121, 221–232. https://doi.org/10.1016/j.biopsycho.2015.10.012 ^
Oskar Flygare
PhD Student in psychology