Mental illness is increasingly recognized as a functional lesion of the brain. In the human brain, complex chemical reactions occur all the time, and various dynamic systems are formed to support human mood, emotion, will and other high-level spiritual activities.

Take depression, for example. Different areas of the brain regulate mood. Researchers believe that nerve cell connections, nerve cell growth, and neural network function are the main factors influencing depression compared to specific brain chemistry.

The latest advances in brain imaging technology have expanded the scope of human understanding of brain science. For example, positron emission tomography (PET), single-photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI) allow for deeper studies of the working brain. fMRI scans can track changes in brain activity in real time; PET or SPECT can record and map the distribution and density of neurotransmitter receptors in specific brain regions.

Using these techniques, it is possible to better understand how different parts of the brain regulate mood and other functions.

An important functional area of the brain

First, some important parts of the brain related to mental illness are briefly analyzed as follows:

Amygdala: The amygdala is part of the limbic system, buried deep in the brain, and is closely linked to emotions such as anger, joy, sadness, fear, and more. Studies have shown that the amygdala is activated when people begin to recall memories with strong emotional factors; When people are sad or clinically diagnosed with depression, the amygdala is more active. This increase in activity persists even after people have recovered from depression.

Thalamus: The thalamus receives most of the sensory information and transmits it to the cerebral cortex (ce).

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tex). It involves high levels of brain functions such as speech, behavioral responses, movement, thinking, and learning. Bipolar depressive disorder can be caused by a problem with the thalamus.

Hippocampus: The hippocampus is also part of the limbic system, which plays a major role in processing long-term memory and recall. The hippocampus and the amygdala function similarly, and it is this part of the brain that causes fear. For example, if a person was bitten by a dog as a child, this terrifying experience causes his brain to have a terrifying reaction when he is faced with a dog barking again when he grows up. The small hippocampus size of some patients with depression also suggests that prolonged mental stress causes damage to nerve cells in their brains.

Neurotransmitters and communication between nerve cells: Neurotransmitters are chemical molecules that help one neuron transmit information to another. It works on the principle that each neuron has a cell body that is closely related to the growth of all cells, and the combination of electrical and chemical signals provides the possibility of communication within and between neurons. When a neuron is activated, it delivers an electrical signal from the cell body to the nerve ending, where the chemical signal is called a neurotransmitter. This signal stimulates specific neurotransmitters to be released into the space between the neuron and the dendrites of adjacent neurons, called synapses. As the neurotransmitter continues to concentrate between synapses, the neurotransmitter molecule begins to bind to receptors buried deep in the membranes of the two neurons.

The release of a neurotransmitter from one neuron can activate or inhibit a second neuron. If the signal is activated or excited, it continues to be transmitted on this particular neural pathway. If it is suppressive, the signal is suppressed. Once the first neuron releases a specific amount of the chemical molecule, a feedback mechanism (controlled by receptors on the neuron) instructs the neuron to stop pumping the neurotransmitter and begin to absorb the transmitter back into the cell membrane. This process is called resorption (

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) or reuptake (

euptake）。

The main function of antidepressant drugs is to regulate the amount of these substances in the neuronal space. In many cases, this change can give the body enough stimulation to ensure that the brain functions better.

A wide variety of neurotransmitters

Scientists have identified a wide variety of different neurotransmitters. Here are some of the neurotransmitters that play a significant role in depressive disorders:

Acetylcholine (Acetylcholi

e), enhances memory, and plays a role in learning and recall.

Serotonin (Se

oto

i

), also known as serotonin (5-HT), assists in regulating sleep, appetite, mood, and inhibiting pain. It is associated with a high risk of suicide.

Norepinephrine (No

epi

eph

i

e), mainly acting on vasoconstriction and raising blood pressure. It has the potential to trigger anxiety and is associated with some types of depression. It also assists in motivational decisions and rewards.

Dopamine (Dopami

e), which plays a major role in motor function. The abnormal transmission is most likely related to a mental disorder, resulting in halluci

atio

S), delusion (delusio

s) and other distorted ways of thinking.

Glutamate, a small molecule substance, is thought to be an excitatory neurotransmitter that plays a role in bipolar depression and schizophrenia. Lithium carbonate is a mood stabilizer used to treat bipolar depression, and studies have shown that it acts to prevent neuronal damage in the brains of rats exposed to high levels of glutamate. Other animal studies suggest that lithium preparations have the potential to stabilize glutamate reuptake, a mechanism that may explain how the drug stabilizes mood during manic periods and improves mood during depressive periods.

γ-aminobutyric acid (GABA), an amino acid that researchers believe is an inhibitory neurotransmitter that has the potential to calm anxiety.

New ideas for healing

So far, medical interventions for depression have been based on neurotransmitter theory. In addition, scientists are exploring the feasibility of other treatment pathways.

Studies have shown that the hippocampus in the brain plays an important role in depression, and some people with depression have a smaller hippocampus. A research team studied 24 women with a history of depression and found that their hippocampal volume was on average 9% to 13% smaller than that of the control group. Women with the most frequent episodes of depression have significantly smaller hippocampal areas. Studies have shown that stress can suppress the production of new neurons (nerve cells) in the hippocampus. It can be inferred that stress factors in depression are likely to be the main cause of hippocampus shrinkage.

If there is a direct link between neoneuron retardation and hypothymia in the hippocampus, this inference will point to the development of antidepressant drugs. In fact, many antidepressant drugs have been developed under the guidance of this theory.

The problem is that a common disadvantage of these drugs is that patients take the drug for at least a few weeks or even longer to see results. This raises the question: if depression is caused by low neurotransmitter levels, why doesn't the patient get better immediately after the neurotransmitter levels increase rapidly?

The answer is likely to be: antidepressants can stimulate and enhance the branching growth of nerve cells in the hippocampus while improving neurotransmitter balance, but this effect only lasts for a few weeks. Mood improvement can only be achieved through nerve growth and new neural connections.

Therefore, there is a theory that the function of existing antidepressant drugs is not to regulate the balance of neurotransmitters in the brain, but to produce new neurons, enhance nerve cell connections, and improve the exchange of information in neural networks.

If this is the case, drugs that specifically promote the production of neurons may be able to cure depression more quickly.