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What is OCD?

OCD is one of the most commonly occurring mental health disorders. It affects about 1% to 2% of people in Western general populations.

It is characterised by recurring intrusive thoughts that are very hard to prevent or control (the obsessions). These lead to irresistible and recurring behaviours (the compulsions or rituals). Compulsions are actions taken to negate or resolve the disruptive, anxiety provoking and disturbing thoughts. A familiar example are those individuals so fearful of “contamination” from everyday activities, such as using a keyboard, touching a doorknob, or handling a notebook, that they feel compelled to scrub their hands with soap and water or a disinfectant many dozens of times a day and despite raw skin from the cleansers. Other unwanted obsessive thoughts can have more disturbing and aggressive themes. Intrusive thoughts/obsessions/compulsions may occur so frequently that they disrupt personal relationships, work, sleep and almost all other aspects of daily life.

Many people experience troubling, unwanted thoughts occasionally. However, in those without OCD, these thoughts are given little importance, do not necessarily compel any actions, and easily disappear. By comparison, in those with OCD, the thoughts or impulses are intense, relentless and can cause tremendous anxiety, guilt, and disgust. The themes of the intrusive thoughts in people without OCD may be quite similar to those occurring in OCD. It is not necessarily the nature of the obsessive thought that defines OCD, but rather how that thought is interpreted and acted upon by the patient.

Regrettably, OCD is usually a lifelong condition that waxes and wanes in intensity and frequency. However, treatment can help manage the obsessions and compulsions, such that are less disruptive.

What causes OCD?

As with numerous other diseases and disorders, there are multiple factors that contribute to the development of OCD. Genetic abnormalities appear to be important; DNA research has found a number of genes that may play roles in OCD. Also, first-degree family members of OCD patients have an increased risk of OCD. Environmental factors, socioeconomic status and level of education) also have been statistically linked to OCD. A single causative factor has not been found in OCD. Rather, it is likely that the above factors and other biological features contribute to OCD behaviours, and also determine the types of symptoms, severity, response to treatments, and course of the illness.  While genetic differences and environmental factors may explain some of the “why” about OCD, the “how” – the mechanisms and biological pathways through which OCD symptoms manifest – is just as important to understand, particularly in the development of better and more focused treatment strategies.

The typical dysfunctional thoughts and actions in OCD appear to result from abnormal levels of or defective neurotransmitters in the brain. Neurotransmitters, derived from amino acids, are the signalling molecules used by nerve cells to communicate and coordinate their activities. They mediate all aspects of brain activities, including things like thought formation, memory, emotion, learning, physical movement, and virtually all other brain functions.

Imbalances or disturbances of several of these neurotransmitters appear to be central in the development of OCD. The neurotransmitters that play important roles in OCD include glutamate, gamma-aminobutyric acid (GABA), serotonin (5-HT), dopamine, and to a lesser extent, norepinephrine. These neurotransmitters are the targets for many of the drugs that have been a cornerstone of OCD treatment.

OCD Subtypes

Although patients with OCD share some clinical characteristics, they frequently have symptoms that are distinctive. Grouping patients according to their principal symptom profile is useful for:

  • Scientific inquiry
  • Clinical information exchange
  • Specific treatment effectiveness
  • Providing patients and their families with realistic long-term expectations


Patients with this subtype have obsessive thoughts that they are contaminated, often from their environment. The person with contamination obsessions can be very fearful and anxious, feelings only relieved by washing and/or decontamination compulsions. These rituals may consume many hours throughout the day.


This subtype is associated with great anxiety and distress from strong yet irrational beliefs  that you failed to do something or made a mistake that could result in harm to yourself or others. Checking compulsions are rituals undertaken repeatedly for reassurance and to relieve the fear and anxiety. Depending on the content of the obsessions, checking can take many forms. Someone might constantly worry that because they did not lock their door, intruders would get in and harm their family. Even if, rationally, they know they locked it, they are still compelled to return to the door and repeatedly check to be sure.


People in this group suffer from intrusive thoughts that if you fail to properly sort or balance objects something bad will happen. Examples include the strong need to have pencils all sharpened to exactly the same height, organizing clothing by colour, or to be obsessive about arranging and rearranging the items on your desk in a precise and inflexible manner. Even finding a message or file that was out of place on your desk can cause distress.


In this group, the obsessive thoughts often have unacceptable (“taboo”) religious, sexual, violent, offensive, or impulsive/aggressive themes. Although these thoughts are not intentional or even characteristic of the affected individuals, they are usually horrifying or repugnant to the patients themselves. Examples are fears of being responsible for violent or sexual harm of loved ones. Importantly, many of the compulsions in this group manifest as mental rather than physical rituals, and as such may not be readily apparent to others unless revealed by the patient.

Mental compulsions are frequently comprised of silent repeating of words or phrases, praying, trying to neutralise the obsessions with positive or safe thoughts, mental checking, and counting. Understandably, patients are often reticent to openly reveal the nature of the intrusive obsessive thoughts because of shame and the fear of being stigmatised by others. Likewise, the silent mental rituals may result in an incorrect diagnosis and suboptimal therapy.

The history of this category of OCD merits brief mention. This subgroup was inaccurately thought to be a strictly obsessive disorder and can be often referred to as “isolated obsessive”, ruminators, or “pure O”.


In this subgroup, individuals usually fear discarding things that might be useful to them someday, or have difficulty deciding whether to keep or discard items. They typically collect, often in tremendous excess, items such as old newspapers and magazines, bottles and containers, mail, and many more that usually are considered by others to have little to no value. The clutter may accumulate to the point that it can cause fires, unsanitary conditions, loss of a great deal of living space, and accident risks. Compared to other OCD subgroups, hoarders tend to have greater levels of anxiety and are comparatively difficult to treat.

At least one-half of hoarders have first-degree family members who demonstrate hoarding-like behaviour. Compared to other forms of OCD, depression and indecisiveness also tend to occur in family members.

There also are several other important differences between hoarding and other OCD subgroups. Although the obsessions of other OCD subgroups are typically uncontrollable and unwanted, patients are quite aware of the extent to which their behaviours are abnormal. By contrast, hoarders usually do not perceive their compulsions as problematic or dangerous. This lack of insight is an obstacle to effective cognitive-behavioural therapy (CBT). Research studies have also shown that the areas of the brain associated with the other subgroups are distinctly different to those in the hoarder form. Finally, clinical research studies of the effectiveness of conventional OCD drugs or CBT have shown mixed results, although recent data show superior outcomes when drug and cognitive-behavioural therapies are combined.

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