How does Dopamine Play a Causative Role in Obsessive Compulsive Disorder

Obsessive Compulsive Disorder (OCD) is currently one of the most common anxiety disorders in the United States, affected around 40 million adults in the US alone. This includes people from the ages of 18 and older, however OCD symptoms begin developing at ages as young as 7 years of age (ADAA 2018).

As time goes on, more and more videos and images are posted, described to trigger your OCD or give you OCD. These images and videos usually consist of unorganised rooms or other things that are just slightly off on aspects such as symmetry and/or order. It is popular amongst adolescents to use the term OCD casually in situations where an individual feels the need to clean something up. Even though this appears to be rather harmless conversational slang, over time this idea of OCD solidifies itself as its common definition. I too used the term OCD loosely to describe some of my family members' behaviors, but after having seen the extent to which OCD can affect an individual's life, I became more critical of my use thereof. I have also had personal experiences with depression, which made me more cognisant of my use of terms with clinical meaning. Therefore, I not only wanted to uncover the ongoing misconceptions about Obsessive Compulsive Disorder, but I also wanted to investigate the biological mechanisms driving OCD.

However, when looking more closely at aspects of OCD I began realising its complexity. Although I will be investigating the biological side of OCD in this paper, it was interesting to get a look at the other perspectives of this complex disorder. No cure exists at this point in time, however there are a variety of different treatments that have been shown to ease symptoms, or at least give patients the feeling of relief, regardless of clinical efficacy. These treatments can range from psychotherapy to various medications that strive to modulate certain neurotransmitters (NT) in the brain.

I chose dopamine (DA), as it is known to be the neurotransmitter in charge of appetitive behaviors and plays roles in addictive behavior. This is important to consider when studying OCD, as the thoughts and behaviors that occur within the disorder consist of repeating thoughts, which are followed by actions to reduce the rising anxiety of the obsessions. Understanding OCD and its chemical mechanisms is a question of particular importance to people who suffer from severe OCD. These individuals will sometimes engage in self harm or in more extreme cases resort to suicide if the obsessive thoughts or compulsions become so bad that they can no longer be controlled. Being able to answer the question of biochemical interactions in key behavioral systems would help to understand OCD and how different symptoms could be treated to reduce or even eliminate them entirely. It is also important to me, as stated previously, to eradicate the notion that this disorder is entirely harmless, and that normal tendencies are in fact very different from the clinical disorder. It is also important that people understand the consequences of having this disorder and know that its origins and manifestations are not fabricated by those affected.

Understanding OCD

Obsessive Compulsive Disorder generally consists of two main parts: the obsessions, and the compulsions. According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) obsessions are recurrent and persistent thoughts, urges, or impulses that are experienced, at some time during the disturbance, as intrusive and unwanted, and that in most individuals cause marked anxiety or distress. Individuals will attempt to ignore or suppress such thoughts, urges, or images, or to neutralise them with some other thought or action; the actions associated with relieving these urges are called compulsions. Compulsions can be characterised as repetitive behaviors or mental acts that the individual feels driven to perform in response to an obsession or according to rules that must be applied rigidly. Therefore, the obsessions can be defined as the mental aspect of this disorder and the compulsions as the physical aspect.

While most people have certain obsessive thoughts and possibly even compulsive behaviors at some points in their lives, it is important to distinguish that these are not equivalent to individuals who suffer from clinically diagnosed OCD. In order for these thoughts and behaviors to be defined as of OCD, the obsessions and compulsions must to become so extreme that they consume larger amounts of time, thus disrupting daily life and other activities.

Generally there are two types of treatment for OCD: psychotherapy or medication. The five most commonly used medication for OCD are the antidepressants Clomipramine, Fluoxetine (Prozac„?), Fluvoxamine, Paroxetine, and Sertraline, all of which are serotonin reuptake inhibitors (SRIs). These medications were tested in a randomised placebo control study and were shown to have a significant effect on OCD symptoms as compared to the placebo (Jefferson, James W. et al). Medications consisting of SRIs and serotonin reuptake inhibitors (SSRIs) do show a positive effect on OCD symptoms, however medications that consisted of just SRIs or SSRIS were significantly less effective in reducing OCD symptoms, rather than medications that inhibit the reuptake of multiple NTs. It is now important to consider why current medication focuses on serotonin reuptake inhibitors (SRIs), rather than directly trying to regulate DA, and why DA still plays a key role.

Understanding Dopamine

Dopamine is a monoamine neurotransmitter that is produced in several areas of the brain including the substantia nigra (SN) and the ventral tegmental area (VTA), and is then released from the hypothalamus into various parts of the frontal lobe. Its main job revolves around controlling the brain's reward and pleasure centers, thus modulating systems of reinforcement. DA controls the brain's reward and pleasure centers by producing both excitatory and inhibitory postsynaptic potentials, depending on the postsynaptic receptor. This is important to be considered, as DA is released when an action or activity is completed, leading to long term potentiation.

Studies have shown dopamines relation to craving, such as drug cravings for example nicotine addiction (Franken, 2003). These studies demonstrated that conditioned drug stimulus produces an increase in DA levels. (Franken). Therefore, it was concluded that DA suppression drives behaviors associated with cravings. Other studies such as Olds' and Milner's 1954 DA research have demonstrated that the stimulation of the nucleus accumbens–an area from which DA is released–caused extreme repetitive behavior in rats. Rats would push a lever, which stimulated the nucleus accumbens, leading to DA release and an increase in synaptic DA concentration. They would even repeat this behavior until they would pass out from exhaustion. A follow up study also showed that they would cross electrified grids in order to push the lever, demonstrating DA's ability as a 'reward neurotransmitter.'

With this it can be suggested that dopamine could play a role in OCD, as DA has been demonstrated to play roles in behaviors similar to those of OCD. Franken demonstrated a relationship between DA and addiction, which share many of the similar features as obsessive thoughts do, while Olds and Milner demonstrated a relationship between DA and compulsive behavior. Therefore, it would not be illogical to consider whether a dysfunction in one of the dopaminergic systems could possibly play a role in parts of Obsessive Compulsive Disorder. It will be discussed to what extent DA plays a role in OCD. It will also be discussed how DA is possibly involved in systems of serotonin (5-HT) and/or norepinephrine (NE), which medical practitioners target for treatment with (S)SRIs and NRIs to decrease the severity of patient's OCD symptoms.

Dopamine and Obsession

Dopamine plays a extremely large role in Motivation. Dopamine's chemical signal gets passed from one neuron to the next, and between those two neurons, DA interacts with various receptors inside the synapse. When these chemical signals are sent through the mesolimbic pathway, which comes from the middle of the brain and branches to various location including the cerebral cortex, they create a reward system, which plays the biggest role in motivation of an individual. What is very important, when considering DA being released for reward and motivation, is that these chemical signals are not sent out as a reward, but as a matter of fact before this. DA performs its tasks before we obtain rewards, meaning that its real job is to encourage one to act. DA is released in anticipation of these rewards. It is also very important to consider that DA is not in charge of pleasure, as studies have demonstrated, higher levels in dopamine being released in soldiers with PTSD for example, when they heard gunshots fired (Liberzon et al., 1999).

The dopamine reward pathways begin in the ventral tegmental area (VTA) and are mainly sent to the frontal cortex (FC). The FC controls important cognitive skills in humans, such as emotional expression, problem solving, memory, language, judgment, and other behaviors. It generally is in control of our personality and our ability to communicate.

One specific connection that we have seen of dopamine to an obsession/obsessive disorder, is in gambling disorders. The gambling disorder is classified as a substance-related and addictive disorder by the DSM-V. Evidence has suggested that individuals who suffer from a gambling disorder have a greater increase in DA levels, in response to gambling stimuli, compared to individuals who did not suffer from this disorder (Joutsa et al.). Here, it is also important to mention that 5-HT is considered to be the most significant NT in abnormal impulsive behaviours (Ib???±ez et al.), which specifically relates to gambling disorder. Evidence suggests that a 5-HT baseline deficit is associated with gambling disorders. In a study, DeCaria et al., interpreted the results, as indicating that individuals with a gambling disorder had a 5-HT postsynaptic receptor hypersensitivity. This demonstrated 5-HT's role in impulsive decision making, which could be translated to obsessive/compulsive behaviours in OCD, as similar 5-HT and DA depressions have been found in OCD patients. 5-HT's relationship to DA however, will be further discussed later in this paper.

On the other hand, a study found that in patients with general anxiety disorder (GAD) also had a decreased availability of the dopamine D2 receptors in the striatum, which was consistent to prior findings in GAD. GAD is an anxiety disorder characterized by excessive, uncontrollable and often irrational worrying about events or activities. With this it could be inferred that DA's effect on GAD could be translated to the obsessions in OCD, as obsessions are defined as recurrent and persistent thoughts, urges, or impulses that are experienced, at some time during the disturbance, as intrusive and unwanted, and that in most individuals cause marked anxiety or distress. (DSM-V) SRIs have also previously been used to treat GAD, which would imply that GAD and the obsessions in OCD affect similar systems in the brain.In Conclusion, evidence suggests that, while dopamine is not the main and only factor affecting OCD, it does play a major role as an intermediate messenger for the system that causes at least parts of OCD. Though there are also parts of DA that affect OCD and are not previously affected by other NTs, medication tests have shown that the relationship of DA to 5-HT and Norepinephrine is a vital part of OCD, as the most effective medications target these three and many more neurotransmitters.

Although this paper demonstrates the importance of dopamine in OCD and medications working against the symptoms of OCD, a better understanding of dopamine's interplay with other neurotransmitters, that play a role in OCD, has to be developed to create better working medications. Future medications that focuses more on dopamine itself for example could cause more problems such as, addiction to the drug itself, movement and motor problems which could either lead to uncontrolled movement similar to that of Parkinson's Disease or restraint of movement controls, and all together motivation loss in patients. Dopamine is such a complex neurotransmitter that affects so many aspects of physical and mental life, that drugs have to be able to limit only very specific dopamine systems if they want to work against OCD. Similarly to how Clomipramine works through serotonin and norepinephrine to control the correct systems of dopamine, still causing a plethora of side effects and not being fully successful in suppressing OCD behaviours/symptoms.

From a broader perspective, investigating solely Dopamine's role in OCD provides only a small insight into the complexities of the disorder. Nonetheless, this understanding adds to the existing knowledge of the neurobiology of OCD, which could ultimately help clarify correlations between other potential factors and OCD. Further research into other neurotransmitters associated with OCD would hopefully help for future advancements in the treatment of Obsessive Compulsive Disorder.

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