Serotonin Deficiency And OCD

Understanding serotonin deficiency 

What is serotonin deficiency?

Serotonin deficiency refers to low levels of serotonin (a type of neurotransmitter – i.e., a chemical messenger in the brain) within the body. More specifically in the brain, which then results in various predominantly negative repercussions. Low serotonin levels are associated with various behavioural and emotional conditions. However, it should be noted that serotonin deficiency affects people differently.

Causes of serotonin deficiency

Researchers aren't sure what causes serotonin deficiency. However, some common potential causes or contributors include:

  • Genetic factors – are linked to the effectiveness of serotonin receptors. The breakdown of serotonin and its absorption, all have an effect on serotonin levels
  • Hormone changes – Can cause neurotransmitter imbalances
  • Lack of physical activity – Physical activity commonly triggers the release of happy hormones, such as dopamine and serotonin which boost your mood. Therefore, lack of exercise means there is less release of serotonin1
  • Chronic stress and/or pain – Prolonged periods of stress deplete serotonin levels2
  • Age-related health and brain changes – The way our bodies and brains function changes as we age.
  • Nutritional deficiencies and/or digestion issues – We require certain proteins, vitamins and minerals for our body to make neurotransmitters. Poor diets or problems breaking down consumed food for physiological use can result in neurotransmitter imbalance
  • Lack of exposure to sunlight or natural light – Lack of vitamin D commonly obtained via sunlight obstructs the production of serotonin.  

Ways to increase serotonin levels

There are various ways to increase serotonin levels which can be achieved through nutrition and diet, supplements, medication and other natural means.

Nutrition and diet 

Serotonin is made from tryptophan, an essential amino acid present in some food items that enter the body through one’s diet. Meat, eggs, dairy, soy products and nuts are some of the examples that typically contain tryptophan. Tryptophan is used by the body to create serotonin therefore eating foods with high tryptophan content can support this process.

Alongside tryptophan, our bodies also require other nutrients, such as vitamins and omega-3 fatty acids to produce serotonin.4 Bananas, beans, leafy greens as well as nuts and seeds are some of the examples containing these key nutrients.


Below is a list of certain supplements that can help boost serotonin levels. However, it should be noted there are also many side effects and interactions associated with such supplements, therefore a healthcare professional should be consulted where necessary.


Certain medications, commonly termed antidepressants, work within the brain to increase serotonin levels. Whilst such medication is commonly used to treat depressive disorders, the action of the drug and its resultant effects (such as improvements in mood and emotional regulation5) also enable it to be taken for other mental health conditions such as anxiety and OCD.

Generally, there are numerous medications that work by increasing the availability of serotonin/norepinephrine in the brain so that neural chemical messaging can operate as it normally would. Essentially, the goal is for the necessary electrical signals in the brain to reach their intended neural region.6

Here are some of the common medication classes that help improve serotonin levels :

  • Selective serotonin reuptake inhibitors (SSRIs)
  • Selective serotonin-norepinephrine reuptake inhibitors (SNRIs)
  • Tricyclic antidepressants (TCAs)
  • Monoamine oxidase inhibitors (MAOIs)

Natural means  

Some natural remedies or strategies that can help boost serotonin levels in the body include:

  • Sunlight exposure – Exposure to bright light can help improve mood, hence why light therapy is a common treatment for seasonal affective disorder (SAD)7 especially during the winter months when there is limited access to bright sunlight. Sunlight is also pivotal for boosting vitamin D levels which is necessary for serotonin production
  • Regular exercise – Exercise, in particular aerobic exercise, can have mood-boosting effects, improves physicality and triggers the release of happy hormones such as serotonin and dopamine
  • o   Practicing meditation – Meditation helps relieve stress and promotes optimism. It is also thought to raise serotonin levels8
  • Massage therapy – Promotes the release of serotonin and decreases cortisol (the body’s stress hormone). Can even be effective when not administered by a trained massage therapist,9 therefore the mere act of receiving a massage has vital benefits

Although there is little scientific evidence to support or reject the use of such strategies in increasing serotonin levels, engaging in such behaviours is unlikely to be harmful.

Understanding OCD

What is OCD?

Obsessive-compulsive disorder (OCD) is a mental health disorder where the affected individual becomes caught in a cycle of obsessions and compulsions. Obsessions are constant, intrusive and repetitive thoughts, images or urges that evoke anxiety and distress. Compulsions are the ritualistic behaviours or mental acts one performs in response to an obsession to reduce anxiety or distress to prevent a feared consequence.`

Furthermore, individuals may sometimes experience relief from their anxiety after performing a compulsion to subside the obsession. However, this does more harm since the obsession has been reinforced and strengthened for the future. Therefore, when the obsession occurs again it will be stronger and arguably more debilitating for the individual thereby increasing the likelihood they engage in the compulsions. Overall, this is essentially how individuals become trapped in a vicious repetitive cycle of their obsessions and compulsions.

Symptoms of OCD – Obsessions

Obsessions are constant, intrusive and repetitive thoughts, images or urges that evoke anxiety and distress. Such thoughts are conceived as illogical however they evoke such intense, undesirable emotions that they can become extremely time-consuming and debilitating, especially when they impact an individual’s ability to function adequately on a daily basis.

Examples of common obsessions in OCD:

  • Contamination obsessions.
  • Sexual obsessions.
  • Violent obsessions.
  • Religious/Moral obsessions.
  • Identity obsessions.
  • Responsibility obsessions.
  • Perfectionism-related obsessions.

Symptoms of OCD – Compulsions

Compulsions are the ritualistic behaviours or mental acts one performs in response to an obsession to reduce anxiety or distress to prevent a feared consequence. Compulsions only provide temporary relief to their compulsions predominantly because they often lack a better coping method. Instead of being a source of pleasure, compulsions are performed because individuals with OCD believe they are necessary to prevent/escape/minimise negative repercussions, anxiety or the presence of obsessions. Similar to obsessions, compulsions are extremely time-consuming and debilitating, especially since they often impact an individual’s ability to function adequately on a daily basis.

Examples of common compulsions in OCD:

  • Washing and cleaning
  • Checking
  • Repeating
  • Mental compulsions (e.g., mental reviews, praying, counting etc.)

Neural Circuitry of OCD 

The cortico-striatal-thalamic-cortical (CSTS) circuit is considered to be the crucial brain circuit implicated in OCD.10 The circuit consists of connections between the prefrontal cortex, striatum and thalamus which are all distinct neural regions.

Commonly thought to play an essential role in information processing and operate as a feedback loop, the CSTC circuit is thought to be dysfunctioning in OCD.11 There are numerous CSTC circuits although there are argued to be OCD-specific imbalances between the ‘direct’ and ‘indirect’ loops of the CSTC circuit.

  • The ‘direct’ pathway forms a self-reinforcing positive-feedback loop which contributes to the initiation and continuation of behaviours
  • The ‘indirect’ pathway provides a negative feedback mechanism, important for inhibiting and switching between behaviours

Glutamate, serotonin and GABA are neurotransmitters that essentially operate as chemical messengers sending signals between different regions in the brain. Glutamate is an excitatory neurotransmitter meaning it promotes the passing of signals between brain regions. Contrastingly, serotonin and GABA are inhibitory neurotransmitters meaning they block or prevent the passage of signals between brain areas.

Importantly, imbalances in these hormones influence the CSTC circuitry by resulting in a hyperactive ‘direct’ pathway and a ‘hypoactive’ indirect pathway.11 Overall, this imbalance in pathway activity causes a ‘brain lock’ signifying that the break that would normally send the feedback loop and control repetition is faulty hence why the vicious cycle occurs.  

Treatments for OCD 

Cognitive behavioural therapy (CBT) is a key form of treatment for OCD. More specifically, exposure and response prevention (ERP), which is a specific type of CBT, provides strong corroborating evidence as a treatment method.12 Typically conducted by a licensed mental health professional in an outpatient setting, ERP is a structured form of psychotherapy whereby the patient is exposed to situations that would provoke their obsessions and their associated anxiety and distress and then instructed to resist the associated compulsions or avoidance behaviours. Ultimately, effective ERP leads to habituation referring to when the person with OCD learns that nothing negative happens when they stop performing their compulsive rituals. Here, the vicious cycle is directly targeted and broken.

Selective serotonin-reuptake inhibitors (SSRIs) medications are another form of treatment for OCD. They work by altering and increasing the serotonin levels in the brain. Despite OCD not being directly caused by serotonin deficiency, increasing levels of serotonin can improve symptoms and responsiveness to psychological treatments.13 Typically, this medication is not intended to be offered as a first-line response for treatment however due to a long waiting list for psychotherapy they are prescribed to help individuals in the meantime by providing some short-term relief.

The relationship between OCD and serotonin deficiency

Little is known about the precise causal role serotonin plays in OCD, instead, it remains plausible that the two are indeed connected. Whilst serotonin plays a role in the CSTC circuitry specific to OCD, its abnormalities are not as profound as that of the GABA and glutamate neurotransmitters. Nevertheless, serotonin is still thought to play a role in OCD.

Notably, the effectiveness of SSRIs, a medication class commonly used to treat OCD, provides evidence for a relationship between OCD and serotonin.13 Abnormalities in the transmission of serotonin are directly combated through SSRIs which work by making more serotonin available at the site of chemical messaging in the brain. In turn, allowing serotonin to stay in one’s system for longer so that it can before its intended duties.

Despite the beneficial effects of increased serotonin activity, this still does not prove that abnormalities in the serotonin system are the root cause of OCD symptoms. Serotonin plays a vital role in modulating various functions within numerous systems where the primary cause(s) of OCD may preside. Future research still investigates the exact relationship between OCD and serotonin.   


Serotonin is a chemical messenger that operates within the brain and plays a pivotal role in various bodily and psychological functions. Therefore, serotonin deficiency (which refers to low levels of serotonin) brings with it many negative repercussions and is thought to be involved in various mental health conditions, in particular obsessive-compulsive disorder. OCD is a mental health disorder where the affected individual becomes caught in a cycle of obsessions and compulsions. Whilst various neural circuitry and chemical activity are thought to be implicated in the disorder, serotonin and OCD are indeed linked. The effectiveness of SSRI medication corroborates this notion however ongoing research still investigates the exact nature of this relationship.


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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jaskirat Kanwal

Masters of Science – MSc, Applied Neuropsychology. University of Bristol, UK

Jaskirat currently works in pharmaceutical care and in the mental health sector. Given their extensive background in psychology, they’re currently seeking to undertake their DClinPsych. They hope to study further, and continue in academia and research, with hopes to ultimately become an HCPC registered clinical neuropsychologist.

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