Understanding the Neurobiology of OCD: Brain Circuitry and Neurotransmitters

While obsessive-compulsive disorder (OCD) is often viewed as a “behavioral disorder,” much more is involved in the development of this condition. More specifically, OCD is actually a “neurobehavioral disorder” meaning that it has both neurological or “brain” and behavioral components. Thus, it is biological (i.e., neurotransmitters) and environmental (external triggers).

To understand the neurobiology of OCD, you must first understand what OCD is and is not. Obsessive-compulsive disorder (OCD) is a chronic, yet common (2-3% of the general population), and often disabling anxiety condition that involves unwanted, intrusive, or upsetting thoughts (obsessions) and/or ritualistic behaviors (compulsions) that are cyclic or repetitive in nature. A compulsion is designed to ease the stress and anxiety causing an obsession. Compulsions typically involve frequent and excessive rituals or routines. There are various types of OCD, ranging from reading OCD to suicidal OCD.

Most OCD sufferers are at least slightly aware that their thoughts and behaviors are irrational and extreme. Still, OCD can and often does lead to significant functional impairment and an increased risk of early death. Although, there is some uniformity among the symptoms that people with OCD experience, current studies suggest that neurobiological processes common to people with OCD, may play an important role in who develops it and who doesn’t and why it is so hard to stop.

OCD is a type of neuro-compulsivity disorder that makes stopping it with sheer will and determination challenging. People who struggle with this type of disorder typically find it almost impossible to stop without OCD help. The first line of treatment for OCD is psychotherapy, specifically, cognitive-behavioral therapy (CBT), exposure-response and prevention (ERP) therapy, and sometimes, other therapies, like acceptance and commitment therapy (ACT), along with medications, like selective serotonin reuptake inhibitors (SSRIs).

Natural remedies like mindfulness meditation, hypnosis, art therapy, and CBD are also sometimes used in conjunction with a prescribed OCD treatment plan to help get OCD symptoms under control. OCD treatment programs like Impulse Therapy, have also shown promise when used alone or as a supplement for other OCD treatments. Researchers suggest that OCD has a neurological component that plays a significant role in its development and progression. The belief is that an imbalance in neurotransmitters (chemical messengers in the brain), specifically serotonin, increases a person’s risk of developing OCD.

However, more research is needed to fully understand the implications of serotonin in the brain and how it contributes to OCD. In this article, we will explore the neurobiology of OCD and the role that brain circuitry and neurotransmitters play in the development and progression of this condition.

What is Brain Circuitry?

A brain circuit, also known as a neural circuit, is kind of like your digestive system, which is comprised of a variety of organs. Each organ is responsible for a different function or task. However, all of these organs must work together to complete the function or tasks, which in that case is breaking down your food, metabolizing the nutrients that come from it, and using the energy gleaned from the nutrients to provide you with energy. The same thing can be said of your brain.

Each region or part of your brain is responsible for a different function or task. However, each region or part must work together to provide energy for your thoughts and movements. The various brain regions communicate through neurons, or “brain wires.” These “wires” create pathways in your brain that guide your thoughts and movement. Understand that your brain is constantly changing and creating “neuron wires.” In fact, your brain consists of billions of “neuron wires” with each one functioning as circuits (an electrical pathway).

Think of the string of lights on your Christmas tree or Halloween lights on your house, well, “neuron wires” behave in the same way only in your brain instead of on your tree or house. Electricity or “power” is transferred to different brain regions through “neuron wires” just like electricity is transferred to different lights on your tree or house through the “electrical wires.” In both scenarios, electricity or “power” is what is needed for them to work – turn on the lights or turn on your brain.

The electricity or “power” in your brain stems from various neurotransmitters like serotonin and dopamine. For your brain to function properly all of these neurons must work together. When there is a “kink” in the “neuron wiring,” it can affect your thinking. In the case of OCD, a neuron disruption can lead to an OCD cycle of non-stop obsessions and/or compulsions. Brain circuitry is the “neuron wiring” that power-ups your brain.

What Are Neurotransmitters and How Are They Linked to OCD?

Neurotransmitters send messages to various parts of the brain, which in turn instructs the body on how to move, behave, feel, etc. Thus, neurotransmitters are chemical messengers in the brain. When the messenger that neurotransmitters are trying to send gets interrupted or if the connection is poor, then it can affect how you think, feel, and behave. Researchers suggest that people with OCD have an imbalance in the neurotransmitter, serotonin.

In fact, people with OCD tend to have low levels of serotonin in the brain (a serotonin deficiency) which leads to non-stop, unwanted intrusive thoughts and repetitive behaviors. Researchers have also found that people with OCD tend to have an excess of dopamine in their brains. Too much dopamine can lead to excessive or chronic stress, anxiety, mania, insomnia, hallucinations, increased movement, addictions, OCD, and other mental health conditions. Some researchers believe that this “imbalance” or “difference” between serotonin and dopamine is the root cause of OCD.

Serotonin and dopamine dysregulation are usually treated with selective serotonin reuptake inhibitors (SSRI) antidepressants, which are meant to restore these neurotransmitters to a healthy level. Also, when these neurotransmitters are interrupted, it impacts the brain circuitry. In other words, disrupted neurotransmitter messages can cause a ripple effect, which also disrupts brain circuits from performing correctly. The result? Stress, anxiety, obsessions, and compulsions.

What is Neurobiology and How is it Connected to OCD?

Neurobiology is the study of the structures and processes of the nervous system. Neurobiology focuses on thinking patterns, behavior, and brain mapping. Biology is combined with psychology to create neuroscience. Understand that the exact cause of OCD is unknown at the time, and this condition cannot be “cured” in the traditional sense, it can be managed.

Researchers suggest that OCD has a neurobiological component because people with this disorder have “abnormal” or increased brain activity in specific brain circuits that transfer “power” or “energy” to the brain regions responsible for planning, motivation, reward, judgment, and mobility. This suggests that an increase in activity in specific brain circuits can increase the odds of a person developing OCD.

While the neurobiology of OCD is still being studied, the general consensus among neuroscientists is that there is a “disconnect” in communication between three parts of the brain – i.e., the cortex, striatum, and thalamus. Pathways in the brain, along with “neuron wires” that transfer “energy” or “power” to these brain regions (cortex, striatum, and thalamus) are involved in the “activation” and the “elimination” (start and stop) of thoughts and behavior. When there is an imbalance in one or more of these circuits or pathways, it can cause an OCD sufferer to get stuck in a non-stop loop of OCD symptoms (obsessions and compulsions).

Are Structural and Functional Changes in the Brain Linked to OCD?

Yes, they are.

Researchers have long suspected that there is a connection between structural and functional changes in the brain and OCD. Specific areas of the brain, specifically, the cortical and subcortical brain regions, involve a group of brain circuits that play various roles in a person’s thought processes and behaviors. Neuroimaging scans suggest that people with OCD have structural and functional abnormalities in the orbitofrontal circuit (orbitofrontal cortices and basal ganglia parts of the brain).

These results support the theory that the origin of OCD stems from brain circuitry that has become maladaptive or has gone “bad.” This theory focuses on maladaptive habit formation and the loss of control or restraint in the parts of the brain responsible for cortically-mediated inhibitory responses (or the ability to hold back or stop certain thoughts and behaviors).

Recent studies also indicate that OCD involves changes that expand across a multitude of frontostriatal loop circuits, and is linked to abnormalities or malfunctions in orbitofrontal cortices and the basal ganglia, located at the base of the forebrain. These two brain regions are responsible for emotions, learning, movement, behavior, decision-making, habit formation, motivation, and emotions – elements that play a role in the development and continuation of OCD.

How Is Grey Matter Linked to OCD?

Studies suggest that people with OCD have larger amounts of gray matter in subcortical brain regions, like the putamen and globus pallidus, and lower amounts of gray matter in the cortex (i.e., ventral, dorsal medial, and inferior frontal cortex regions of the brain). The cortex is responsible for emotional and behavioral control, decision-making, problem-solving, conscious thought, body movement, memory, language, and personality.

Large amounts of gray matter in the subcortical brain regions are linked to non-stop intrusive thoughts and repetitive behaviors or movements. Although gray matter disruptions are more significant in the brains of people with OCD, there are also disruptions in white matter, albeit a bit smaller. White matter in the brain is responsible for nervous system functions. Disruptions in white matter can lead to impulsivity, memory issues, poor decision-making skills, uncontrolled movements, intrusive thoughts, compulsions, etc.

Does the Size of Brain Structures and Regions Play a Role in the Development of OCD?

Yes, it does.

Neuroimaging scans suggest that people with OCD tend to have reduced cortical thickness. Cortical thickness refers to the number of neurons in a specific part of the brain). Results suggest that OCD sufferers have less density in the frontal, parietal, and temporal parts of the brain. Moreover, these individuals also tend to have less fiber density, axonal diameter, and myelination in white matter in various brain regions, such as the anterior midline tracts, parts of the corpus callosum, and the cingulate bundle. These abnormalities in the brain can lead to OCD symptoms – obsessions and compulsions.

What Do Neuroimaging Scans Suggest?

Well, neuroimaging scans, also referred to as brain scans, have found some irregularities in the brains of people with OCD. One scan found brain structure abnormalities in OCD sufferers that were not found in people who do not have the condition. These findings suggest that OCD may be linked to smaller amounts of hippocampal and larger amounts of palladium (brain regions responsible for storing memories and linking them to events, and regulating voluntary movements).

However, the scan did not indicate that there was a difference in the caudate nucleus or putamen (brain regions responsible for the execution of movement, the creation of memories, learning, motivation, and reward). Mental health conditions like OCD have been linked to reduced cortical thickness in the frontal, parietal, and temporal cortical brain regions. Thus, researchers suggest that people with OCD have structural brain abnormalities located beyond the classic orbitofrontal loop brain circuit.

Researchers have also found irregularities in how disrupted brain networks function during rest and periods of task-related brain activity. A meta-analysis exploring the functional connectivity of the brain’s resting state found that people with OCD have a hypo-connectivity within and across some brain circuits, and dysconnectivity (no specific changes in connectivity) in other brain circuits. In the past, neuroimaging scans exploring OCD focused on impaired motor inhibitory control, cognitive flexibility, and executive planning. However, researchers have begun to examine the brain circuitry in people with this disorder. Imaging is now being used to evaluate the potential foundation of cognitive tasks by measuring the activity of various brain regions and exploring the functional connectivity or the “relationship” between these regions.

Another meta-analysis exploring the inhibitory control tasks of OCD sufferers found that these individuals experienced less brain activity in the rostral and ventral anterior cingulate cortices, bilateral thalamus/caudate, right anterior insula/frontal operculum, supramarginal gyus, and orbitofrontal cortex regions of the brain. Neuroimaging scans also suggest that OCD sufferers and their asymptomatic close relatives are likely to experience a reduction in functional connectivity between the anterior and posterior cortical regions in their brains, especially during cognitive tasks that involve movement.

Researchers also found that “coupling” between the ventrolateral prefrontal cortex and dorsal caudate nucleus may lead to “worsening” in OCD symptoms – i.e., obsessions and internal compulsions. Conversely, researchers also found that dysconnectivity or a “disconnect” between the cortex and basal ganglia (putamen) in the brains of OCD sufferers and their close asymptomatic relatives may be a “marker” for OCD. Thus, neuroimaging scans suggest that OCD may be linked to scattered, indefinite, structural, and functional brain changes that involve both the orbitofrontal loop and other brain circuits.

Can Neuroimaging Scans Detect OCD?

No, it can not.

Although changes have been detected when comparing the brains of OCD sufferers to those without them on neuroimaging scans, these “changes” appear to be minor or indistinct (vague or unclear). In other words, they can not be seen on an OCD sufferer’s neuroimaging scan. There is also no reliable and valid neuroimaging scan algorithm that can be used to accurately diagnose OCD.

There are limited classifying scans that are used as a predictive model that can assess multivariate patterns so that participants with OCD can be separated from the control group or those without OCD during studies. Still, even in these cases where they are used to predict or classify OCD, these findings should not be used to diagnose OCD.

Final Thoughts

There are many theories as to why a person develops OCD. Most researchers agree that OCD has both biological and environmental origins, however, exactly how these biological and environmental origins intertwine or “connect” are still somewhat a mystery. Some studies suggest that the biological factors stem from a “disconnect” or “imbalance” in certain brain regions, while others suggest that “abnormal” brain structures, excess gray matter, and reduced white matter are the main culprits. Yet, others believe that miscommunication between neurotransmitters is the true cause of OCD.

Neuroimaging scans have provided researchers and neuroscientists with a clearer glimpse into the neurological variances between people who have OCD and those who do not. Still, more research is needed to understand the neurobiology of OCD. The hope is that with more research and a better understanding of how OCD manifests in the brain, more effective treatments can be created specifically for OCD.

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