OCD And Its Effect On The Brain

Obsessive-compulsive disorder (OCD) is a severe psychiatric disorder in which patients feel compelled to perform specific actions repeatedly, often to stop the distress caused by certain thoughts or fears (obsessions).

Obsessions are intrusive and persistent thoughts that cause distress, for example, fears of contamination or taboo thoughts. Compulsions are actions you feel you must do to reduce the distress caused by the obsession, such as constant handwashing or praying.

OCD affects up to 3%¹ of the general population, making it a relatively common condition. But it isn’t just about being a hygiene freak or becoming overly religious. OCD gets so severe that it has adverse effects on quality of life. Today, we know that OCD changes how the brain works.

As early as the 1980s, researchers were already studying the effects of OCD on the brain. Using positron emission tomography (PET) scans, they studied blood flow and energy usage² (metabolism) in various brain regions in 14 people with confirmed OCD.

The scans showed distinct differences in an OCD brain compared to a normal “control” brain. The regions the researchers singled out include the orbitofrontal cortex and the basal ganglia.

Since then, more research has confirmed that OCD changes the brain significantly. Findings like these helped classify psychological issues such as OCD as medical health problems.

Have you considered clinical trials for Obsessive compulsive disorder (OCD)?

We make it easy for you to participate in a clinical trial for Obsessive compulsive disorder (OCD), and get access to the latest treatments not yet widely available - and be a part of finding a cure.

OCD brain: Stuck in a loop of “wrongness”

A popular hypothesis (scientific perspective or model) suggests that OCD results from incorrect information processing. More specifically, the brain fixates on a potential “threat” in the environment and overcompensates to mitigate it.

Let’s say that you touched the door of a public restroom or a seat on an airplane. Your brain identifies the risk of exposure to harmful germs as a threat. It then triggers a direct action in a brain region called the basal ganglia to act on this threat, such as washing your hands with soap or using hand sanitizer.

In a healthy individual, once the action is done (i.e., washing your hands), an indirect pathway in the brain should kick in and stop further action on the perceived threat.

However, in a person with OCD, the basal ganglia are overly excited. They become hyperaware of threats like this, so accidentally touching something they perceive as dirty becomes a trigger.

This region’s high level of activity triggers repetitive action, such as obsessive hand sanitization. It also inhibits or obstructs the indirect pathway meant to stop the action, further worsening the problem.

More importantly, whenever you take action against the perceived threat, you experience a temporary sense of relief, which triggers the brain’s reward center. This reinforces the irregular response and leads to compulsive behavior, a toxic negative loop of “wrongness.”

This is a simplistic way of understanding OCD and its effects on the brain. More recent research³ suggests that OCD is much more complex. It affects several brain areas, including the orbitofrontal cortices, cingulate gyri, and thalamus.

OCD brain vs normal brain: The differences

Through imaging, surgical, and lesion studies, research findings⁴ suggest that regions in the prefrontal cortex, basal ganglia, and thalamus are involved in the development of OCD.

Prefrontal cortex

The orbital cortex is a region in the brain’s prefrontal lobe responsible for decision-making. Decision-making is complex and involves cognitive processes such as:

  • Response inhibition—the ability to resist an action if it is inappropriate or illogical

  • Inferred value—the ability to estimate the value of action after assessing the environment

  • Emotional processing

  • Social behavior

  • Mistake or error detection

The last factor is significant when it comes to OCD. If you perform a task correctly or exceptionally well, the prefrontal cortex lights up and makes you feel good and accomplished.

On the other hand, failure to perform a task or doing it poorly makes you feel miserable.

This is the brain’s natural system to help you grow essential skills and avoid costly errors. In people with OCD, this region is hyperactive and causes them to feel as if something is wrong even when there isn’t. 

For people with OCD, their brain keeps telling them that they made a mistake and have to correct it, for example, by washing their hands again and again or rechecking that they turned off the oven. Even though they know they haven’t done anything wrong, the intense reaction in the orbital cortex compels them to repeat the action.

The cingulate gyrus

Working hand-in-hand with the orbital cortex, the cingulate gyrus is part of the limbic system involved in pain and emotional interactions. It predicts and helps us avoid the negative consequences of our actions and plays a role in motivation and behavioral responses.

The cingulate gyrus links an emotional response to the learning signals sent to the prefrontal orbital cortex. For example, if you make a mistake, it causes a feeling of discomfort or anxiety until you fix it.

This means that people with OCD can’t just walk away from a mistake they (think they) have made. For example, they can’t forget that they haven’t washed their hands (enough). The cingulate gyrus will make them uneasy and anxious until they fix the mistake. They usually have to do it repetitively to relieve these feelings of anxiety.

Basal ganglia and the caudate nucleus

After the prefrontal cortex recognizes a threat in the environment, it activates parts of the brain called the basal ganglia. More specifically, it activates a component within the basal ganglia known as the caudate nucleus.

The caudate nucleus is responsible for:

  • Procedural learning—the ability to acquire motor skills and perform automatic actions

  • Associative learning—learning from linked events, such as feeling pain when you touch a hot stove

  • Inhibitory action control—the ability to stop impulsive actions or create responses through reasoning

This last function is the key to overriding irregular compulsions and obsessions. It allows the brain to “change gears” when faced with anxieties and impulses that are out of control. 

Suppose you were on vacation and started wondering whether you locked your front door before you left. Your caudate nucleus is supposed to help you realize that it is unrealistic to return home just to lock your door, so you should just forget about it and continue your day.

However, people with OCD have less grey matter volume in the medial frontal gyrus, the medial orbitofrontal cortex, and the left insulo-opercular region. The caudate nucleus cannot help someone with OCD overcome irrational compulsions, so they repeatedly try to fix the mistake.


The thalamus sits between the caudate nucleus’s lobes near the brain’s center. Its chief role is to relay information from the body’s senses (except smell). Studies⁵ have shown higher volume in the thalamus of children with OCD.

Researchers think this is the heightened activity that OCD triggers in other parts of the brain, such as the prefrontal cortex and basal ganglia. That’s because the thalamus has parallel circuits with these regions, which researchers believe are vital in understanding OCD.

Errors and stop signals

The understanding of a brain with OCD unlocks many important discoveries. Patients are fully aware of their errors and perceived threats and take action to correct them. However, their brain does not respond to stop those signals after fixing the error.

This is clearly illustrated in reduced activity in the caudate nucleus. With weak “stop” signals, a person with OCD cannot stop compulsively taking action against their hyperactive sense of awareness of mistakes.

Disconnected brakes

Researchers at the University of Michigan confirmed this theory while conducting a large study⁶ involving more than 500 participants. It involved brain scan data from people worldwide and showed that those with OCD had more activity in error-recognition areas but far less in brain regions that could help them stop.

The researchers suggested that there could be an “inefficient linkage” between these two brain systems. They compared it to having a car with your foot on the brake but no actual connection to the brake pads that could help you stop.

What causes OCD?

Research⁷ suggests that the most significant risk factor for OCD is genetic. If someone in your family has OCD, you could likely develop it too.

Environmental factors also play a prominent role in the development of OCD. Even with genetic vulnerability, OCD has high associations with other factors such as:

  • During pregnancy—high weight gain, water retention (edema), and prolonged labor

  • Childhood maltreatment—neglect and significant emotional, sexual, or physical abuse

  • Stress or trauma—stress increases the risk factor for people with a genetic vulnerability to OCD 

We know very little about what causes and drives the behavior of patients with OCD. It is also unclear whether the various brain differences are the causes or the effect of OCD. 

It is like saying men tend to be tall, but you can’t predict whether a tall person is a man or a woman. We just don’t know enough to make those kinds of predictions.

However, understanding how OCD affects specific areas in the brain and behavioral processes may tell us how to stop the OCD loop.

Treatment of OCD 

Scientists already know that OCD is primarily due to a failure in communication between the brain’s frontal cortex and its deeper parts (such as the thalamus and basal ganglia). These regions use neurotransmitter chemicals such as serotonin to communicate.

Increasing serotonin levels in the brain helps improve communication and enables the patient to overcome OCD compulsions. 

OCD medication is used together with cognitive behavioral therapy to help you face your fears. Often, it involves triggering your obsessions while resisting the compulsion to “make things right.”

Your therapist will work with you to break down the mental, emotional, and physical parts of your OCD responses. This psychological therapy is usually sufficient for mild OCD, but severe cases often require months of therapy and medication before you start seeing results.

OCD support groups can also help you find reassurance, moral support, advice, and a chance to socialize with others and feel accepted. Positive reinforcement is essential to help break the negative loop and reintroduce positive behavior.  

The lowdown

In people with OCD, the part of the brain responsible for recognizing and reacting to errors and threats is hyperactive. However, the part responsible for recognizing that the threat or mistake has been corrected is hampered by insufficient communication.

Due to this, people with OCD are unable to stop themselves from compulsively acting on their obsessions, such as handwashing or religious actions. This becomes a negative loop of wrongness, but it can be corrected with medication and psychological therapy.

Frequently Asked Questions

Is OCD a brain disorder?

Yes, OCD is now classified as a brain disorder, not just an anxiety disorder. This follows a more accurate understanding of how the condition affects brain mechanisms and how patients struggle to control their impulses and compulsive behavior.

Is PANDAS the same as OCD?

PANDAS is short for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections. It occurs when a child diagnosed with a strep infection suddenly displays OCD symptoms. Most children recover from PANDAS with treatment when the infection clears.

Can OCD lead to brain damage?

OCD fundamentally changes the brain, showing a significant reduction in grey matter density in some regions. In severe cases, this can permanently change how the brain works for patients with OCD. However, most people can lead normal and happy lives with therapy and medication.

Have you considered clinical trials for Obsessive compulsive disorder (OCD)?

We make it easy for you to participate in a clinical trial for Obsessive compulsive disorder (OCD), and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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