What Causes CNS Depression? (+9 Long-Term Effects)

In this comprehensive guide, we will talk about what Central Nervous System depression or CNS depression means, symptoms, most common cause, overdose symptoms and addiction-related signs. 

Central Nervous System Depression: What is it?

In simple terms, Central nervous system depression is considered a physiological state, resulting from inhibited or suppressed activity in your brain, which can cause reduced heart rate, loss of consciousness that could lead to coma or death. 

Your central nervous system consists of your brain and the spinal cord.

The brain is the one in charge of controlling your body, not only physically but mentally speaking. It gives orders to the organs in your body as it is the case of the lungs, for you to breath, and your heart, for it to keep beating and pumping blood through your body.

On the other hand, the spinal cord handles nerves and their impulses, allowing your brain to be in constant communication with the rest of your body.

Psychologically speaking, it is also responsible for how you feel, think and interact with everything around you. 

When the Central Nervous System slows down its activity, that’s when it is called CNS depression.

This is not necessarily dangerous and sometimes slowing down might be necessary, but if it slows down too much then that is when it can become life-threatening.

Remember, the brain is one of the most, if not, the most important organ in the human body.

So we need to be careful about the type of substances we are letting in. 

What are the symptoms of CNS depression?

When the activity in your brain gets reduced or becomes slow then that is when you can feel relaxed and less anxious.

This is why sedatives or CNS depressants work to treat anxiety and sleeping problems like insomnia. 

Additionally, in some cases, you might also experience drowsiness, lack of coordination or slurred speech.

If the CNS keeps slowing down then symptoms like reduced ability to make judgments, slower heart rate or breathing, feeling tired or confused may start to show.

It might also lead to coma or delirium if not treated on time.

What causes CNS depression?

The intake of certain medications can interfere with the correct or appropriate functioning of your brain’s activity, even consuming drugs or alcohol can be responsible for CNS depression.

Here we mention some of the most common depressant drugs. 


They are also called “downers” and can generate a sense of euphoria or relaxation. Regarded as highly addictive even under small dosages.

This is why they are no longer commonly used to treat conditions such as anxiety or sleeping problems like insomnia. 

They are also considered very powerful and can be used as anticonvulsants, they are also commonly prescribed prior to having surgery so it can help you relax during the procedure. Some of the commercial names are Mebaral, Nembutal or Luminal Sodium.


These specific types of drugs are considered safer than barbiturates and are most commonly prescribed to treat anxiety and sleeping problems.

Some of the most prescribed are Xanax, Valium, and Ativan. They are mostly known for their sleep-inducing, sedatives, and muscle-relaxing properties.


They are commonly used for pain relief and some of the common ones include codeine, Vicodin, Kadian, and Percocet.

They are classed as the most addictive and dangerous drugs in the world since overdosing can become extremely fatal. 

Sleeping medications

As you know, they are prescribed to help as a sleeping aid for people with insomnia.

Some of the most common are Lunesta, Sonata, and Ambien. 

Medical conditions

Some medical conditions might result in CNS depression when they are considered chronic and some could be diabetes, thyroid problems, liver or kidney disease. 

Brain Injury

Decreased blood flow and oxygen to your brain increase the chance of developing CNS depression.

This includes suffering from brain injury, brain aneurysm, tumors, strokes, infections, and trauma due to accidents. 


The degree in which your brain is affected by this substance depends on how much and how fast you have ingested it.

At first, you might feel relaxed and inhibited but the more you drink, the likelihood of a negative emotional response arises.

It has been said that alcohol can even increase the risk of anxiety and stress rather than reduce it, as it is thought.

This could also elicit aggressive behaviors and depression. 

Ingesting or inhaling certain chemicals can be responsible for CNS depression.

A clear example would be ethylene glycol, which is present in antifreeze or de-icing products. If it gets ingested, it can be very toxic to your brain.  

Effects of CNS depressants

CNS depressants work by increasing the production of a neurotransmitter called GABA, which is related to reduce your brain activity and produces a sense or feeling of being relaxed.

Some of the effects also include dilated pupils, lowered blood pressure, confusion, sleepiness or fatigue, difficulty concentrating,  memory loss, euphoric episodes, reduced inhibitions, and impaired judgment, to name a few. 

Long term use can also produce negative effects depending on the type of depressant and the severity of misuse.

Chronic abusers, in particular, may develop tolerance and will require a dosage increase to keep having the same effects.

Some potential negative long-term effects include:

  • Chronic fatigue
  • Weight gain
  • Hypersomnia
  • Sexual dysfunction
  • Breathing and sleep difficulties
  • Depression
  • Suicidal thoughts
  • Physical dependence
  • Addiction

These depressants of the central nervous system can become highly addictive and you can develop a substance use disorder or SUD.

Additionally, long term use, even when prescribed, can cause tolerance in some cases, where it becomes necessary for you to take higher and higher doses or increase the frequency to achieve the same effect. 

Signs of misuse or abuse

People abusing CNS depressants will normally tend to steal depressants from other people, intensify the dose to maximize the effect without any medical approval or without being indicated. Other warning signs could include:

  • If the person is constantly having mood swings.
  • If they are secretive about what they are doing or if they display atypical behavior.
  • They go into periods of depression or apathy.
  • They have a lack of energy or motivation towards life.
  • Have withdrawal symptoms when not using the medication.
  • If they have failed in their attempt to stop.

CNS withdrawal symptoms

If you discontinue the intake of CNS depressants it might lead to withdrawal.

Since the use of CNS depressants cause the brain chemistry to change and slows the activity, withdrawal symptoms tend to appear when stopping the medication abruptly. 

These symptoms are said to begin typically 12 to 24 hours after the last dose of the drug and can reach their peak (get worse) 12 to 24 hours after this dose.

Some of the symptoms begin to fade on their own after this period but some might still be present up to 24 months.

This is known as post-acute withdrawal symptoms or PAWS. 

Some of the most common symptoms are listed as follows:

  • Insomnia
  • Restlessness
  • Nausea
  • Vomiting
  • Shaking
  • Weakness
  • Excessive sweating
  • Irritability
  • Hallucinations
  • Anxiety
  • Panic attacks
  • Body tremors
  • Seizures
  • Depression
  • Muscular stiffness or pain
  • Changes in perception
  • Heart palpitations
  • Tension
  • Stress
  • Memory issues
  • Increased blood pressure and pulse
  • Hypersensitivity to light and sound
  • Aches and pains

To avoid withdrawal symptoms from depressants, and avoid any life-threatening complications, it is important to be medically assisted for a detox. 

Why is this blog about CNS depression important?

We have discussed what CNS depression means and that is not all the cases where your brain activity slows down means there is a problem or a sign that something is not right.

However, when the brain activity gets reduced at the very lowest then that is when we can consider it alarming and life-threatening. 

Additionally, it is important to keep into consideration and raise awareness, about the possible signs and symptoms, causes and course of action in case of an emergency due to an overdose or drug abuse.

Also, it is helpful to know when someone is going through withdrawal or is having difficulties with regular activities due to their addiction to CNS depressants and how we can help them and point them into a successful recovery.  

Side Note: I have tried and tested various products and services to help with my anxiety and depression. See my top recommendations here, as well as a full list of all products and services our team has tested for various mental health conditions and general wellness.

Frequently Asked Questions (FAQ’s) about CNS depression

What are symptoms of CNS depression?

Symptoms can include feeling sleepy or losing coordination, blurred vision, unable to think clearly, unable to locate yourself in time and space, reduced reflex reaction and sensitive to pain.

What causes CNS depression?

CNS depression happens when your body’s normal brain functioning slows down.

This could be the result of a drug overdose, poisoning or medical conditions.

Depression of your CNS often occurs when there is substance abuse or misuse.

Do CNS depressants cause depression?

Due to the term “depressant” being related to depression, people might think depressants cause people to feel depressed but this is not the case. 

What are examples of CNS depressants?

Some of the most common and well-known examples of CNS depressants are benzodiazepines, barbiturates, and even certain sleep medicines.

CNS depressants are usually called sedatives or tranquilizers due to their effect in the brain. 

What is CNS toxicity?

Central nervous system (CNS) toxicity may result from exposure to a vast array of foreign substances or unknown substances to the human body.

They are termed as Xenobiotics

  1. Neuroscience of Pain, Stress, and Emotion: Psychological and Clinical Implications
  2. Frontiers in Clinical Drug Research – CNS and Neurological Disorders: Volume 6
  3. Nerve Cells and Nervous Systems: An Introduction to Neuroscience
  4. Depression and Drugs: The Neurobehavioral Structure of a Psychological Storm (SpringerBriefs in psychology)
  5.  Depression and Brain Dysfunction


Addiction center

Medical News Today


National Institute on Drug Abuse

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