The Gut-Brain Axis: The Human Gut Microbiome and Anxiety and Depression: Difference between revisions
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==Mood Disorders== | ==Mood Disorders== | ||
Mood disorders are mental health conditions that affect one’s emotions and behaviors[49]. They include depression disorders, anxiety disorders, and manic disorders. The development of mood disorders is not fully understood, but genetics and environmental factors seem to play a role in the progression of these forms of disorders [7]. Additionally, there is evidence suggesting one’s neuroticism is a predictor for the development of a mood disorder [67]. | |||
There are differences in prevalence of mood disorders based on sex. For example, in the United States, women are more likely to be diagnosed with a stress-related mood disorder than men [68]. All diagnoses of mood disorders come from the DSM-5, the standard manual of mental disorders with the diagnostic criteria and treatment options for every form of mental disorder known. It was published by the American Psychiatric Association in 2013, and a revised version of the DSM-5 was published in 2022.<br> | |||
<br> | <br> | ||
===Depression=== | |||
Major depressive disorder is one of the most common mood disorders. It can be present in 121 million people at once [3] and symptoms include low mood or anhedonia and changes to physical and physiological functions [7]. Many people with depression have episodes beginning during adolescence, and these episodes are recurrent [4, 7]. | |||
Depression can develop for a multitude of reasons. “Susceptibility genes, neurochemical imbalances, brain circuitry dysfunction, faulty information processing, negative cognitions, social or environmental sources of vulnerability, and precipitating stressors” [7] are all potential reasons for the development and progression of depression. | |||
One of the key causes of depression is through genetics. Genetic influences are similarities of depression measures that increase with shared genes [7]. Families are used to study this cause of depression by comparing parents with depression and the number of their offspring with depression [7]. Twin studies compare behavior between identical and fraternal twins. Since both twins have the same family or possible common environment, this form of study shows the overall impact of genes and is the strongest piece of evidence for the heritability of depression [7]. | |||
In major depressive disorder, the most common genetic markers are involved in serotonergic neurotransmission [7]. Serotonin is a neurotransmitter that is involved in mood, reward, and memory [50]. Abnormalities in serotonin have been linked with the pathophysiology of depression [7]. | |||
===Anxiety=== | |||
While day to day anxiety is common, anxiety disorders are another common mood disorder, characterized by uncontrollable feelings of anxiety and fear that impair one’s social, occupational, and personal activities [64]. It affects about 16.4% of the population or around 40 million people in the United States [20]. Symptoms of anxiety include fatigue, restlessness, difficulty concentrating, increased heart rate, and chest pain [64]. There are many types of anxiety disorders, including generalized anxiety disorder, social anxiety disorder, obsessive-compulsive disorder, panic disorder, and post-traumatic stress disorder. | |||
Norepinephrine and serotonin are two important neurotransmitters for anxiety disorders. Norepinephrine is a neurotransmitter involved in the fight or flight response, or the acute stress response, and it has been shown to increase alertness and to constrict blood vessels [52]. It is involved in the pathogenesis and regulation of anxiety disorders. Serotonin, in addition to its involvement in major depression disorder, is involved in the pathophysiology of OCD and other anxiety disorders [21]. | |||
===Treatments=== | ===Treatments=== | ||
Treatment options for both anxiety and depression disorders are similar, including various therapies, medications, and lifestyle changes. The first line of treatment is typically some form of therapy, whether it be cognitive behavioral therapy (CBT) or more specific forms, like exposure and response prevention (ERP). CBT is focused on changing cognitions, such as thoughts, beliefs, and attitudes, and behaviors associated with those cognitions while also developing coping strategies [65]. | |||
Due to the involvement of serotonin, selective serotonin reuptake inhibitors, or SSRIs, are one of the common drugs used for the treatment of depression and anxiety disorders. These drugs work by blocking the reuptake molecules responsible for bringing serotonin molecules back into the neuron [51]. This allows serotonin to stay outside of the neuron for longer periods of time and have more effects on the brain. | |||
SNRIs are another common form of medication. These are selective norepinephrine reuptake inhibitors and have a similar mechanism of action as SSRIs [66]. While there are a variety of treatments available for both depression and anxiety, there are forms of mood disorders that are treatment resistant, meaning they do not respond to any form of treatment available. | |||
==The Gut-Brain Axis== | ==The Gut-Brain Axis== | ||
Revision as of 02:38, 12 April 2024
Introduction
By Samantha Lee
Humans have evolved throughout the many years with microbes. Microbes play an important role in not only human health but also human disease. The human intestinal tract contains a wide variety of microorganisms, all of which have a large impact on health and disease [1]. This microbiota has recently been studied more in depth as researchers discovered that microbes have a larger impact on human health than once understood. Antibiotics and diet have been shown to alter the diversity of the gut microbiota, leading to the possibility of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) since patients with IBS and IBD have been shown to have unstable gut microbial populations [2].
The human gut contains a large number of microbes that live in the gastrointestinal tract of humans and other animals [53]. These microbes play an important role in digestion, metabolism, and immune function. They can ferment food and supply nutrients and energy to a host and to its immune systems [44]. The intestinal microbiota has a wide diversity of microbial species, and this community of bacteria colonizes the gastrointestinal tract after birth [2]. There are around 40,000 bacterial species that are influenced by vertical transmission from one’s mother, genetic makeup, diet, medications, gastrointestinal infections, and stress [2].
The human gut microbiota can be grouped by three major bacteria enterotypes: Bacteroides, Prevotella, and Ruminococcus [9]. Bacteroides are Gram-negative, obligate anaerobic bacteria. They make up a significant portion of the human fecal bacterial population [54]. Prevotella is another Gram-negative bacteria, and it is thought to have a common ancestor with Bacteroides [55]. It is more common in the gut of individuals who eat primarily a diet filled with carbohydrates, since it is able to break down fibers and plant glycans [56, 57]. Ruminococcus, on the other hand, is an anaerobic, Gram-positive bacteria. Certain species of Ruminococcus have been found to be less prevalent in individuals with IBD [58]. Treatment with antibiotics can affect the intestinal gut microbiota and can cause lifelong changes to the makeup of this community.
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Legend/credit: Magnified 20,000X, this colorized scanning electron micrograph (SEM) depicts a grouping of methicillin resistant Staphylococcus aureus (MRSA) bacteria. Photo credit: CDC. Every image requires a link to the source.
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Mood Disorders
Mood disorders are mental health conditions that affect one’s emotions and behaviors[49]. They include depression disorders, anxiety disorders, and manic disorders. The development of mood disorders is not fully understood, but genetics and environmental factors seem to play a role in the progression of these forms of disorders [7]. Additionally, there is evidence suggesting one’s neuroticism is a predictor for the development of a mood disorder [67].
There are differences in prevalence of mood disorders based on sex. For example, in the United States, women are more likely to be diagnosed with a stress-related mood disorder than men [68]. All diagnoses of mood disorders come from the DSM-5, the standard manual of mental disorders with the diagnostic criteria and treatment options for every form of mental disorder known. It was published by the American Psychiatric Association in 2013, and a revised version of the DSM-5 was published in 2022.
Depression
Major depressive disorder is one of the most common mood disorders. It can be present in 121 million people at once [3] and symptoms include low mood or anhedonia and changes to physical and physiological functions [7]. Many people with depression have episodes beginning during adolescence, and these episodes are recurrent [4, 7].
Depression can develop for a multitude of reasons. “Susceptibility genes, neurochemical imbalances, brain circuitry dysfunction, faulty information processing, negative cognitions, social or environmental sources of vulnerability, and precipitating stressors” [7] are all potential reasons for the development and progression of depression.
One of the key causes of depression is through genetics. Genetic influences are similarities of depression measures that increase with shared genes [7]. Families are used to study this cause of depression by comparing parents with depression and the number of their offspring with depression [7]. Twin studies compare behavior between identical and fraternal twins. Since both twins have the same family or possible common environment, this form of study shows the overall impact of genes and is the strongest piece of evidence for the heritability of depression [7]. In major depressive disorder, the most common genetic markers are involved in serotonergic neurotransmission [7]. Serotonin is a neurotransmitter that is involved in mood, reward, and memory [50]. Abnormalities in serotonin have been linked with the pathophysiology of depression [7].
Anxiety
While day to day anxiety is common, anxiety disorders are another common mood disorder, characterized by uncontrollable feelings of anxiety and fear that impair one’s social, occupational, and personal activities [64]. It affects about 16.4% of the population or around 40 million people in the United States [20]. Symptoms of anxiety include fatigue, restlessness, difficulty concentrating, increased heart rate, and chest pain [64]. There are many types of anxiety disorders, including generalized anxiety disorder, social anxiety disorder, obsessive-compulsive disorder, panic disorder, and post-traumatic stress disorder.
Norepinephrine and serotonin are two important neurotransmitters for anxiety disorders. Norepinephrine is a neurotransmitter involved in the fight or flight response, or the acute stress response, and it has been shown to increase alertness and to constrict blood vessels [52]. It is involved in the pathogenesis and regulation of anxiety disorders. Serotonin, in addition to its involvement in major depression disorder, is involved in the pathophysiology of OCD and other anxiety disorders [21].
Treatments
Treatment options for both anxiety and depression disorders are similar, including various therapies, medications, and lifestyle changes. The first line of treatment is typically some form of therapy, whether it be cognitive behavioral therapy (CBT) or more specific forms, like exposure and response prevention (ERP). CBT is focused on changing cognitions, such as thoughts, beliefs, and attitudes, and behaviors associated with those cognitions while also developing coping strategies [65].
Due to the involvement of serotonin, selective serotonin reuptake inhibitors, or SSRIs, are one of the common drugs used for the treatment of depression and anxiety disorders. These drugs work by blocking the reuptake molecules responsible for bringing serotonin molecules back into the neuron [51]. This allows serotonin to stay outside of the neuron for longer periods of time and have more effects on the brain.
SNRIs are another common form of medication. These are selective norepinephrine reuptake inhibitors and have a similar mechanism of action as SSRIs [66]. While there are a variety of treatments available for both depression and anxiety, there are forms of mood disorders that are treatment resistant, meaning they do not respond to any form of treatment available.
The Gut-Brain Axis
Include some current research, with at least one figure showing data.
Bifidobacterium
Lactobacillus
Other Evidence
Current Research
Vagus Nerve Stimulation
Conclusion
References
Authored for BIOL 238 Microbiology, taught by Joan Slonczewski,at Kenyon College,2024
