The vagus nerve, linking brain and gut through its afferent and efferent branches, is a critical route in the bidirectional communication of this axis. Directly or indirectly, the vagus afferent fibers can sense and relay gut microbiota signals to the brain and induce brain disorders including depression.
Depression leads to changes in autonomic control of the body and changes the autonomic balance in favor of an increased sympathetic tone, which can be detected with fair accuracy with HRV analysis.
Depression, like most other major psychiatric illnesses, is widely accepted to be caused by neurochemical imbalances in regions of the brain that are known to control mood, anxiety, cognition, and fear. These regions include the hippocampus, prefrontal cortex (PFC), cingulate cortex, nucleus accumbens, and amygdala.
If your mood systems are functioning normally, called “euthymia,” when you have reason to be happy, neurotransmitters are released and brain systems activated that make you feel happy. And, when you have reason to be sad, neurotransmitters get released and brain systems activated that make you feel sad.
Our nervous system is involved in every function of the Human Body, including Anxiety and Depression symptoms.
There's no single cause of depression. It can occur for a variety of reasons and it has many different triggers. For some people, an upsetting or stressful life event, such as bereavement, divorce, illness, redundancy and job or money worries, can be the cause. Different causes can often combine to trigger depression.
In depression, the amygdala is overactive and responds excessively to negative events. In turn, the amygdala connects to a set of brain regions that hone the physiological and behavioral response to emotional stimuli.
Depression and chronic pain share some of the same neurotransmitters -- brain chemicals that act as messengers traveling between nerves. Depression and chronic pain also share some of the same nerve pathways in the brain and spinal cord.
The amygdala is responsible for the expression of fear and aggression as well as species-specific defensive behavior, and it plays a role in the formation and retrieval of emotional and fear-related memories. (Fig. 2 depicts the amygdala's involvement in fear circuitry).
Depression causes the hippocampus to raise its cortisol levels, impeding the development of neurons in your brain. The shrinkage of brain circuits is closely connected to the reduction of the affected part's function. While other cerebral areas shrink due to high levels of cortisol, the amygdala enlarges.
People with clinical depression often have increased levels of monoamine oxidase A (MAO-A), an enzyme that breaks down key neurotransmitters, resulting in very low levels of serotonin, dopamine and norepinephrine.
The study, which gathered evidence from 361 peer-reviewed scientific studies, found no link between depression and serotonin levels in the blood.
The biological factors that might have some effect on depression include: genes, hormones, and brain chemicals. Depression often runs in families, which suggests that individuals may inherit genes that make them vulnerable to developing depression.
Causes of low serotonin
age-related health and brain changes. chronic stress. a lack of exposure to natural light. lack of physical activity.
The vagus nerve connects the brain with the major organ systems of the body. It links mental and physical processes. It is the means by which the mind and body are physiologically inseparable; signals that affect one directly affect the other, although they find expression in different ways.
The vagus nerve is the body's superpower and it's used to counteract your fight/flight system. It's how you develop a healthy stress response and become resilient. When stimulated, you feel calmer, more compassionate, and clearer. Stimulating the vagus benefits your autonomic nervous system and mental health.
Evidence shows that stimulating and strengthening the vagus nerve can reduce the symptoms associated with mental health challenges. What is vagus nerve stimulation? Vagus nerve stimulation (VNS) involves using a small, surgically implanted device to stimulate the vagus nerve with electrical impulses.
If you or a loved one is suffering from depression, visiting a neurologist can help provide some clarity.
NYU Langone offers an experimental treatment called deep brain stimulation, which may ease severe symptoms of depression that are not adequately controlled by therapy, medication, or electroconvulsive therapy.
It's often said that depression results from a chemical imbalance, but that figure of speech doesn't capture how complex the disease is. Research suggests that depression doesn't spring from simply having too much or too little of certain brain chemicals.
In healthy subjects, serotonin appears important for this automatic avoidance. It has long been suggested that over-activity of the serotonin system may relate to mood disorders such as depression and anxiety, as these seem characterized by too much withdrawal and avoidance.
Major depression.
The classic depression type, major depression is a state where a dark mood is all-consuming and one loses interest in activities, even ones that are usually pleasurable. Symptoms of this type of depression include trouble sleeping, changes in appetite or weight, loss of energy, and feeling worthless.