"The awakening of Kundalini gives liberation to yogis, but gives the fool the shackles of suffering." (*1)

I researched Kundalini syndrome (or Zen disease).

Symptoms:
- Heat accumulates in the body, leading to distraction and hindering daily life.
- Headache, nervousness, high blood pressure, arrhythmia, inability to concentrate.
- The location where heat accumulates includes the lower body, heart, and head. It is accompanied by intense heat or a feeling of pressure.
- Hands and feet become cold.
- Incessant crying.
- Sometimes accompanied by hallucinations, delusions, and insomnia.
- Symptoms similar to autonomic nervous system dysfunction.
- In some cases, it can lead to death.

Possible causes of the symptoms:
- Insufficient grounding.
- Energy flow within the body is blocked. Negative thoughts obstruct the flow of energy.

Solutions:
- Circulate energy within the body.
- A method called "En-ten-ho" circulates energy from the Muladhara chakra to the Sahasrara chakra along the spine, then through the front of the body, and back down to the Muladhara chakra, balancing the energy. When lowering energy from the front of the body, be mindful of grounding.

This En-ten-ho method is simple but very effective. People with Kundalini syndrome have heat accumulating in their bodies, so simply performing the above energy circulation can dramatically improve their condition, or they may recover within a few weeks.
En-ten-ho is included as a basic practice in some yoga styles, and it is a method that can be practiced regularly even for those who do not experience Kundalini syndrome, but have energy stagnation in their bodies.

The factors that block energy are specific to each chakra:
- Muladhara chakra in the lower body: Overcoming sexual desires is necessary. Overcoming karma, including past lives, is necessary.
- Svadishthana chakra in the lower body: Overcoming sexual desires is necessary. Overcoming unconscious, dormant karma is necessary.
- Anahata chakra (heart): Negative emotions can cause blockage, so it is important to be optimistic.
- Visuddha chakra (throat).

The awakening of Kundalini is ideally something that should be done under the guidance of a teacher, but sometimes it can spontaneously awaken in people who are not prepared, leading to various symptoms. In particular, when the Muladhara chakra or Svadishthana chakra awaken, all suppressed emotions can explode, making it more likely to develop Kundalini syndrome. In such cases, guidance from an appropriate teacher is necessary.

The Kundalini energy is often understood in a simple way, as rising from the lower body to the head. However, with this general understanding alone, the energy can become blocked in the head. In some cases, the Sahasrara chakra, located above the head, may open, allowing the energy to be released, but if the energy cannot be released and becomes blocked, it can lead to what is known as Kundalini syndrome or Zen disease.

Kundalini rises along the spine. From there, it passes through the front of the body and goes down. This part is what is called "grounding," and the more grounded one's life is, the better the energy flows downwards. If one lives a frivolous life, the energy may not flow downwards easily. Even if one abandons social life and immerses oneself in mysticism, it may be difficult to achieve grounding.

There seem to be various variations of the En-ten method, but simply moving the body back and forth can be effective. Some variations involve passing the energy through the back of the body and then the front, and then raising it again along the spine to the head, and then lowering it through the inside of the body to the dantian.

In any case, the basic principle of the En-ten method is that the energy rises from the back and descends through the front of the body (grounding). This alone seems to improve the symptoms of Kundalini syndrome or Zen disease.

References:
Tao Human Medicine
https://books.google.co.jp/books?id=oTSLrxoa86YC&printsec=frontcover&hl=ja#v=onepage&q&f=false
Esoteric Yoga
http://www.shukyoshinri.com/shop/%e5%af%86%e6%95%99%e3%83%a8%ef%bc%8d%e3%82%ac-%e2%80%95%e3%82%bf%e3%83%b3%e3%83%88%e3%83%a9%e3%83%a8%ef%bc%8d%e3%82%ac%e3%81%ae%e6%9c%ac%e8%b3%aa%e3%81%a8%e7%a7%98%e6%b3%95%e2%80%95/

■Postscript
Later, while researching about Nāda sounds, I unexpectedly learned more about Kundalini. I will write about it in detail in a separate article, but in short, in yoga, the Nadis (energy channels in the body, meridians), specifically the Sushumna, which runs along the spine, become blocked with impurities, leading to Kundalini syndrome.

The En-Ten method itself doesn't necessarily prevent Kundalini syndrome. Rather, practices like the En-Ten method are similar to what is called "purification" or "clearing." It seems that if you awaken Kundalini without first performing various clearings and purifications, it can cause tremendous chaos. Details are written at the end of the link provided above.

■Addendum 2
Since then, something similar to a Kundalini experience occurred. I have added details to the page related to the "nada" sound, which is the same as the link above.

■Addendum 3
Recently, I realized that when consciousness shifts to the crown of the head, what is called Kundalini syndrome occurs, and I feel that consciousness becomes hazy. When that happens, I move my consciousness from the crown of the head to the back of the head, or rather, I lower it to the back of the head, and it becomes stable, which is what is called a "grounding" state. In this state, consciousness becomes clear, and it no longer feels like Kundalini syndrome. It doesn't seem that this itself is Kundalini syndrome, but I realized that the sensation changes significantly depending on where you place your consciousness, not just performing the "minor circulation."

Normally, in what is called a "grounding" state, the seat of the soul or consciousness seems to be in the back of the head. Before, I didn't even recognize where the seat of consciousness was, and I didn't know where it was, but recently, I've become aware of the location of consciousness, and when I direct consciousness to a certain part of the body, the seat of consciousness moves slightly.

This is a little different from spiritual practices where you are told to "feel the Earth" or "imagine it." Indeed, when you imagine the Earth, consciousness tends to move slightly downward, and that may cause consciousness to move from the crown of the head to the back of the head. However, regardless of whether you imagine the Earth or not, simply consciously and forcefully moving consciousness from the crown of the head to the back of the head seems to create a grounding state.

This is just my experience, and I don't know if others will experience the same thing.

There is a "bindu chakra" located in the upper part of the back of the head, but the grounding position is not there, but rather lower, around the area of the pineal gland. It is also stable when lowered further, near the "vishuddha chakra," which is minor, but near the "Chibukam Chakra," which is not often seen elsewhere. When you lower it to the "vishuddha chakra," it feels like it's too low. The "Chibukam Chakra" is mentioned in "Meditation Yoga: Soul's Serenity" by Vasudeva Naia Iyengar, and it is said that the Iyengar family has been teaching it this way. The "Chibukam Chakra" is located slightly below and behind the pineal gland, between the "vishuddha chakra" and the pineal gland.

■Addition 4
In "The Secrets of Yoga" (by Koichi Ohyama), regarding countermeasures for Kundalini syndrome or Zen sickness, it mentions C.W. Leadbeater's book and states, "When ending meditation, return the Kundalini to the Muladhara." I checked the original text of "Chakras" (by C.W. Leadbeater), and it reads as follows:

Kundalini gradually ascends through the Sushumna channel as the yogi focuses their mind for meditation. It may not rise much at first, but next time it will rise a little more, so this is repeated many times. (Omitted section) When ending meditation, the Kundalini is returned to the Muladhara (root chakra) through the same path. However, in some cases, it may be returned to the heart chakra. "Chakras" (by C.W. Leadbeater). The Sushumna channel is a channel within the main Nadis.

In my case, I feel more comfortable returning it to the back of my head rather than the Muladhara. In fact, I feel like returning it to the Muladhara might disrupt the balance, so I return it to the back of my head.

(*1) From Chapter 3, verse 107 of the Hatha Yoga Pradipika. The translation is from "Chakras" (by C.W. Leadbeater).