Can Parasitic Infections Cause Depression?

What is Depression?

Depression is a mood disorder that causes persistent feelings of sadness, despair, and loss of interest. It may also alter the way a person behaves, reacts, and functions daily. According to a 2012 study, major depressive disorder (MDD) remains among the most common mental disorders, with a 16.6% lifetime prevalence rate in the United States. Pharmacological treatments and therapeutic methods may be used; however, new-generation antidepressants do not produce clinically significant improvements in depression in patients who initially have moderate or even very severe depression, but show significant effects only in the most severely depressed patients. Drug–placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for severely depressed patients.

A 2007 study stated “it is also usually highly recurrent, with at least 50% of those who recover from a first episode of depression having one or more additional episodes in their lifetime, and approximately 80% of those with a history of two episodes having another recurrence.”

There are many reasons why depression reoccurs in an individual. However, today we will take a look at parasitic infections and poor gut health as root causes for depression.

Can Parasites Cause Depression?

Absolutely - parasites can cause depression. When parasites infect an individual, they begin making small, subtle changes to the body and mind as they mark their territory. Once they have established residency, they start to cause other symptoms:

Gut Issues (food sensitivities, IBS, abdominal pain, constipation/diarrhea, unexplained nausea)
Insomnia / Grinding Teeth when Sleeping (bruxism)
Anal Itching
Acne / Psoriasis / Inflammation of the Skin
Sugar Cravings / Increased Hunger
Fatigue / Flu-like Symptoms
Muscle & Joint Pain
Heart Palpitations / Chest Pain
Iron-deficiency Anemia
Brain Fog
Unexplained Weight Gain / Difficulty Losing Weight
Worsening Symptoms During the Full Moon
Schizophrenia
Anxiety
Depression

Click here to check out our article on the causes and symptoms of parasitic infections!

Parasites cause depression by disrupting neurotransmitters, altering the gut microbiota, and by causing inflammation.

1) Disrupting Neurotransmitters: Neurotransmitters are chemical messengers that are released and received by the brain’s nerve cells, also known as neurons. Neurons are consistently communicating to each other by exchanging neurotransmitters. This process is crucial for a healthy brain.

In order for the brain to efficiently send and receive signals, the neurons need to be connected. A small space called a synapse connects neurons to each other. As a package of neurotransmitters crosses the synapse, they can be chosen for a specific chemical on postsynaptic cells. For example, dopamine receptors chose to carry dopamine molecules.

Imbalances in these chemicals may cause depression. The three main neurotransmitters associated with depression are norepinephrine, serotonin, and dopamine. Other notable neurotransmitters associated with depression are glutamate, GABA, and acetylcholine.

When the communication between neurotransmitters and neurons are weak, a person is at a higher chance to experience depression symptoms. Similarly, insomnia, irritability, brain fog, and fatigue may occur when this type of communication is weakened.

Parasites may interfere with levels of neurotransmitters within the body. They change the ways nerve cells release neurotransmitters like serotonin and GABA. Essentially, they turn the host’s brain chemistry against them. For example, parasites may interfere with GABA, the neurotransmitter that calms the body and mind. If a parasite clings to a GABA receptor, it causes major disruption for that specific neurotransmitter. A reduction in GABA may cause slow digestion, ADHD, anxiety, muscle pain, headaches, and depression.

Another example includes the intracellular parasitic protozoan, T.gondii. This parasite often passed through cats is known to cause toxoplasmosis. According to a 2015 study, “although mild flu-like symptoms occasionally occur during the first few weeks following exposure, T. gondii infection does not usually produce observable symptoms in healthy humans. However infection can cause serious illnesses in immunocompromised hosts, infants, and pregnant women. Infection can also be transmitted transplacentally from the mother to the fetus.” The CDC states that this infection is detectable in over 40 million people in the United States.

T. gondii may hide in the body for decades without being seen by medical testing as the parasite becomes encysted, creating a brick-like barrier between testing and the infection. According to a 2011 study, T. gondii infection is known to be associated with raised dopamine levels in particular. Dopamine levels are also often raised within patients with schizophrenia. It has also been observed that “the Toxoplasma genome contains two copies of a gene encoding an enzyme with tyrosine hydroxylase activity, the rate limiting enzyme in the synthesis of l-3,4-dihydroxyphenylalanine (L-DOPA), precursor to dopamine.” This may create symptoms of depression and schizophrenia.

A 2003 study stated that “Toxoplasma infections have demonstrated that this organism affects levels of dopamine, norepinephrine, and other neurotransmitters.” Another 2011 study stated that “the observed effects on dopamine metabolism could also be relevant in interpreting reports of psychobehavioral changes in toxoplasmosis-infected humans.” Overall, parasites act as a remote control to the brain as they choose how the brain and its nerve cells function.

2) Altering the Gut Microbiota: Parasites create nutritional deficiencies to nourish themselves and create significant gastrointestinal inflammation. For example, acetylcholine, the chief neurotransmitter of the parasympathetic nervous system, is eaten by parasites. This neurotransmitter assists in regulating heart rate/blood vessels and maintaining gut mobility. As parasites feed off of this neurotransmitter, blood becomes thinner and the gut becomes more immobile. Since this can create constipation and low motility, more infections and parasites may invade the body as it is in a vulnerable state. This can also create food sensitivities and depression.

According to a 2017 study, “95% of the body’s serotonin is produced in the intestine where it has been increasingly recognized for its hormonal, autocrine, paracrine, and endocrine actions.” Once parasites invade the gut, they may rob the body of serotonin. Serotonin is the key hormone that stabilizes our mood. If imbalanced, depression, anxiety, panic attacks, and other mental disorders may occur. A compromised gut creates a compromised brain.

Cryptosporidium parvum, Giardia duodenalis, Trypanosoma cruzi, A. lumbricoide, Schistosoma species and others alter gastrointestinal motility, absorption, or secretion. For example, “recent estimates suggest that A. lumbricoides can infect over a billion, T. trichiura 795 million, and hookworms 740 million people (3). Although intestinal helminths rarely cause death, they instead create autoimmune and chronic diseases that have insidious effects on health and nutritional status of the host.”

Nutritional deficiencies of vitamin A, iron, zinc, vitamin B12, magnesium, molybdenum, vitamin D, and more have been known to be caused by parasites. These deficiencies can lead to an unhealthy mind as these nutrients are needed to have a properly functioning brain.

The gut is the body’s second brain. The gut and brain are in constant communication with each other. However, if communication is compromised by pathogens, it will interfere with a person’s mental health. Parasites are known to cause inflammation in the gut and brain. For example, irritable bowel syndrome (IBS/IBD), celiac disease, and Crohn’s disease are all disorders that create an inflammatory bowel response. Research shows that intestinal parasites can affect the immune system of infected hosts and in some cases, they are able to modify and change the host’s immune responses, particularly in autoimmune disorders like celiac disease and IBD.

A 2014 study stated that “opportunistic infections in patients with IBS are common. These infections include viral infections (herpes viruses, human papillomavirus, influenza virus, and JC virus), bacterial infections (tuberculosis, nocardiosis, Clostridium difficile infection, pneumococcal infection, legionellosis, and listeriosis), fungal infections (histoplasmosis, cryptococcosis, Pneumocystis jiroveci infection, aspergillosis, and candidiasis), and parasite infections (Strongyloides stercoralis).” A diagnosis of IBS raises the risk of depression and anxiety.

For example, it was reported that blastocystis infections were found in 67% of the patients with IBS and it could be a serious problem for diagnosis of IBS. Similarly, it was found that post-infectious bowel dysfunction following Giardia infection is associated with increased duodenal mucosal in IBS patients. Research has also proven that T. trichiura could be misdiagnosed due to its ability to mimic IBS symptoms.

Alterations to the gut-brain axis, intestinal microbiota, and the neuro-immune system is the reason for the relationship between IBS and depression. Parasites may cause all three of these systems to act imbalanced. This invites depression to attack the body as the sympathetic and parasympathetic nervous systems are trying to regulate themselves.

A 2018 study stated that “the association of IBS and mood disorders has long been documented; the associated inflammation that occurs due to alteration in gastrointestinal tract microbes and increased cytokines causes oxidative stress leading to damage in areas of the brain such as the hippocampus and amygdala involved in the etiology of depression and other mood disorders.” Pathogens such as bacteria, viruses, and parasites can cause this inflammation and alteration in gastrointestinal microbes.

3) Causing Inflammation: Parasitic infections create general inflammation in the body as it attempts to rid itself of the infection. Like any other infection, the body sends pain signals to the brain if there is a harmful pathogen within the body. Parasites can cause acute and chronic inflammation as different species create unique symptoms.

For example, parasitic liver fluke infections can be a cause for non-alcoholic fatty liver disease. According to a 2019 study, this type of infection “provokes chronic inflammation leading to periductal fibrosis by inducing the expression of hepatic pro-inflammatory cytokines (e.g., tumor necrosis factor-α and interleukin-1), pro-inflammatory transcription factor (nuclear factor kappa B), and inducible nitric oxide synthase.” This infection is also correlated with cholangiocarcinoma (CCA).

Liver fluke infections are also significantly associated with cholangitis, cholecystitis, cholelithiasis, hepatocellular carcinoma and cholangiocarcinoma.

Aside from a parasite's physical symptoms in regards to inflammation, parasites can also cause significant mental and emotional symptoms due to inflammation. For example, a pinworm infection (oxyuriasis) is easily transmitted among people, it has an extremely high prevalence in overcrowded conditions, such as nurseries and primary schools. It is extremely common in children. Symptoms of a pinworm infection are diverse ranging from nausea, diarrhea, insomnia, irritability, recurrent cellulitis, loss of appetite, nightmares and endometritis. One study stated that “anxiety disorder, depression, and sleep disorder were higher in the pinworm infections group (p < .001) than the unexposed group.” Previous studies have also correlated that infectious or inflammatory diseases were associated with psychiatric disorders, such as dementia, mood disorders, and learning disability.

Pinworms can cause inflammation in children that severely affects their mental stability, sometimes creating depression and/or anxiety.

Another example of depression stemming from inflammation due to parasitic infections includes toxocariasis, a parasitic infection that can cause fatigue, seizures, blurred vision, and skin rashes. This infection may also cause depression as it inflames the central nervous system. According to a 2015 study, there are “various cognitive deficits associated with infection, including a lack of developmental progress and speech, depressive symptoms and cognitive deficits possibly indicative of dementia, mental confusion and cognitive impairment, impairments of mental fluency and short-term and working memory spans, and slowed information processing.”

If you believe you are dealing with chronic illness, please contact a functional provider. Dr. Jaban Moore, a functional medicine provider, can help you if you are experiencing chronic symptoms.

Please reach out if you are interested in taking your health back! You can give our office a call at (816) 889-9801.

References:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4005415/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2169519/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5680167/#:~:text=Irritable%20bowel%20syndrome%20(IBS)%20is%20a%20functional%20gastrointestinal%20disorder%20of,to%20be%20linked%20to%20IBS

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5520446/

https://www.tandfonline.com/doi/abs/10.3109/13590849009003131

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772764/

https://www.frontiersin.org/articles/10.3389/fncel.2015.00452/full

https://www.cdc.gov/parasites/toxoplasmosis/gen_info/faqs.html#:~:text=Toxoplasmosis%20is%20an%20infection%20caused,infected%20with%20the%20Toxoplasma%20parasite

https://pubmed.ncbi.nlm.nih.gov/2420295/

https://pubmed.ncbi.nlm.nih.gov/12853170/