Hallucinogens’ Effects on the Brain


Humans have been ingesting mind-altering substances, including hallucinogens, for centuries. During the 1960s, hallucinogens helped shape the art, music and consciousness of the era’s counterculture. Are hallucinogens substances with vast therapeutic potential that can also open doors to unlimited creativity or are they extremely dangerous substances that can destroy lives? Maybe hallucinogens are both of these.

Exactly What Are Hallucinogens?

Hallucinogens are a class of substances that alter a person’s perceptions of their surroundings as well as their thoughts and feelings. They induce hallucinations, which is when a person perceives images or sensations that are not present. Hallucinogens may also cause illusions, where a person misperceives an object or sensation that is actually present. Some hallucinogens cause people who use them to feel disconnected from their bodies or out of control. Hallucinogens are categorized as classic or dissociative. They can be synthetic or extracted from mushrooms and other plants. Some common classic hallucinogens are: 

Common dissociative hallucinogens:

How Do Hallucinogens Work in the Brain?

It is thought that classic hallucinogens act on neural circuits in the brain that use serotonin in order to produce their effects. The brain’s prefrontal cortex is involved in perception, cognition and mood, and this is where the most prominent hallucinogenic effects occur. Hallucinogens also manifest effects in areas of the brain that control arousal and physiological stress responses.  

Short-Term Effects of Hallucinogens 

Ingesting hallucinogens will cause people to hear and see things and feel sensations that are not there. They also distort objects and sensations that are real. The onset of effects is usually within 20 to 90 minutes and duration varies but can last up to 12 hours. Other possible short-term effects of classic hallucinogens are:

  • Dizziness 
  • Sense of relaxation
  • Nervousness or paranoia
  • Otherworldly imagery
  • Elevated heart rate, blood pressure and body temperature 
  • Uncoordinated movements
  • Agitation
  • Introspective and spiritual experiences
  • Changes in time perception
  • Mixed senses (seeing music or other sounds)
  • Ayahuasca tea can cause severe vomiting

Long-Term Effects of Classic Hallucinogens

Although rare, long-term hallucinogen use can lead to persistent psychosis or hallucinogen persisting perception disorder (HPPD). Persistent psychosis is a series of continuing psychiatric problems, which can include paranoia, mood changes, visual disturbances and disorganized thinking. HPPD is the recurrence of drug experiences–such as visual hallucinations–days, weeks, months or even over a year after the use of the drug. 

Short-Term Effects of Dissociative Hallucinogens

The effects of dissociative hallucinogens can start to be felt in a few minutes and can last for hours. Some people who use them have even reported feeling lingering effects for days. Effects depend on the dosage. Short-term effects of small doses of dissociative hallucinogenic use are:

  • Numbness
  • Lack of coordination and disorientation
  • Elevated body temperature

Short-term effects of these drugs in higher doses can cause:

  • Seizures
  • Panic and anxiety
  • Psychosis
  • Inability to move
  • Difficulty breathing
  • Amnesia 

Long-Term Effects of Dissociative Hallucinogens

Currently, more research is needed on the long-term effects of dissociative hallucinogens. It is known that PCP can cause addiction when used repeatedly. Other effects can go on for a year or more even after stopping the use of the drug, including:

Hallucinogens and Overdose

When someone overdoses, they consume enough of a drug to cause adverse effects that are serious and can even cause death. While classic dissociative hallucinogens can cause unpleasant side effects, they are generally not life-threatening. 

Some of the dissociative hallucinogens are more likely to lead to overdose. For example, high doses of PCP can cause coma, seizures and even death. There is an increased risk of coma when PCP is combined with alcohol or benzodiazepines. 

Can Hallucinogens Be Addictive?

In some cases, hallucinogens can lead to addiction. PCP can be addictive as people who stop using it after repeated use can experience withdrawal symptoms. LSD, on the other hand, is not considered addictive because it does not lead to uncontrolled attempts to obtain the drug. People who use LSD do develop tolerance and have to use higher amounts of the drug to get the same effect. Due to the drug’s unpredictability, this can be dangerous. 

While behavioral treatments can be helpful for patients with a variety of addictions, scientists need more research to find out if behavioral therapies are effective for addiction to hallucinogens.

Dangers of Mixing Hallucinogens with Other Substances

Ingesting hallucinogens while using other substances can lead to serious complications. When you use hallucinogens and consume alcohol, the combination can lead to decreased coordination. It can also cause increased vomiting, leading to aspiration. Using hallucinogens and stimulants can result in increased heart rate and increased stress on the body. It can also cause increased anxiety.

While there are no FDA-approved medications to treat hallucinogen addiction, help is available at Casa Palmera. If you are struggling with hallucinogen use, we offer a variety of treatment modalities that include a combination of western medicine and ancient eastern intuitive therapies. At each level of care, an individualized treatment plan is developed for each patient to address their unique needs. We provide aftercare plans and post-discharge support in the form of our alumni group and our app. Call Casa Palmera today at (855) 508-0473.


This blog is for informational purposes only and should not be a substitute for medical advice. We understand that everyone’s situation is unique, and this content is to provide an overall understanding of substance use disorders. These disorders are very complex, and this post does not take into account the unique circumstances for every individual. For specific questions about your health needs or that of a loved one, seek the help of a healthcare professional.