An altered state of consciousness is any condition that is significantly different from a normal waking state, where a person’s awareness, perception, or mental functioning changes in noticeable ways.
When we talk about altered states of consciousness, we are referring to experiences where the mind is aware but not in its usual wakeful condition. These states can range from very mild shifts in awareness to profound transformations in how we perceive ourselves and the world around us. The term was first used in relation to medical conditions like epilepsy in 1904, and later became more widely used in academia starting in the 1960s when researchers began studying these phenomena more systematically.[1]
There is no single agreed-upon definition of altered states of consciousness, largely because scientists cannot fully agree on what constitutes a “normal” state of consciousness in the first place. However, one influential definition describes altered states as any mental conditions induced by various physical, psychological, or drug-related means that can be recognized by the person themselves or by an observer as representing a sufficient deviation from that person’s normal alert, waking consciousness.[1]
Epidemiology
Altered states of consciousness are remarkably common in human experience. Research shows that nearly all societies engage in practices that lead to altered states of consciousness, and humans have been using various methods to induce these states for more than 30,000 years.[5] In ancient civilizations, excessive dancing, meditation, and mind-altering plants were used to modulate the activity of the mind, and these practices continue across cultures today.[3]
From a medical perspective, altered mental status accounts for approximately five percent of adult emergency department visits in the United States.[9] This makes it the seventh most common emergency that emergency medical services professionals respond to, accounting for almost seven percent of all emergency calls.[12] These statistics highlight how frequently these conditions affect people’s health and require medical attention.
Certain populations are at higher risk for experiencing altered states of consciousness as medical emergencies. Older adults are especially susceptible to conditions like delirium, which is a sudden change in mental function that causes confusion and disorientation. Studies show that delirium affects between three and twenty-nine percent of older adults admitted to hospitals for medical conditions. After hip fracture surgery, the rate jumps dramatically to between twenty-eight and sixty-one percent of patients. In intensive care units, between sixty and eighty percent of patients on breathing machines experience delirium.[9]
Spontaneous altered states also occur with notable frequency in the general population. Approximately fifteen percent of people at some point in their life experience an out-of-body experience, which is the sensation of being located in space away from one’s physical body. This number increases to sixty-five percent among people who come close to death and survive.[4] Another type of altered state experience, after-death communications, are reported by anywhere from thirty to fifty-five percent of people at least once in their lifetime.[4]
Causes
Altered states of consciousness can arise from an enormous variety of causes, which can be broadly divided into those that occur naturally or intentionally in healthy individuals, and those that result from medical conditions or emergencies. Understanding the difference between these categories is crucial because they require very different responses.
In healthy individuals, altered states can be induced through numerous natural methods. Sleep is perhaps the most universal altered state, one that every person experiences daily. During sleep, particularly during the REM stage (rapid eye movement), the brain enters a state where vivid dreams occur and consciousness is fundamentally different from waking awareness.[3] Other natural methods include meditation, where prolonged practice leads to states of relaxation and heightened awareness, and physical exercise, especially intense activities that can trigger the release of chemicals called endorphins, leading to feelings of euphoria or altered awareness.[13]
Various breathing techniques can also induce altered states. Holotropic breathwork, for example, involves regulating and speeding up breathing patterns to influence physical, mental, and emotional states.[11] Music, hypnosis, fasting, sensory deprivation, and even sexual activity are additional methods through which people can naturally experience shifts in consciousness.[3]
From a medical standpoint, altered mental status can result from problems affecting nearly any organ system in the body. Issues with the central nervous system, such as brain bleeding, brain tumors, seizures, or stroke, can directly disrupt normal consciousness.[6] Metabolic disturbances represent another major category of causes. These include dehydration, low blood sugar, low oxygen levels in the blood, low sodium or calcium levels, and thyroid problems. Each of these conditions affects the chemistry of the brain in ways that can alter consciousness.[6]
Infections throughout the body can also trigger altered mental states. Urinary tract infections, brain infections like encephalitis or meningitis, and pneumonia are all known to cause changes in consciousness, particularly in older adults.[6] Medications and substances form yet another important category. Adverse reactions to prescription drugs, including anti-seizure medications, drugs that control involuntary muscle movements, steroids, sedatives, and sleeping pills can all alter consciousness. Drug overdoses or withdrawal from substances like opioids and alcohol can cause dramatic changes in mental state.[6]
Physical trauma to the brain, whether from accidents or falls, can result in altered consciousness that may be temporary or long-lasting. Various types of shock, including shock from heart problems, can reduce blood flow to the brain sufficiently to change consciousness.[6] In some cases, the cause may be increased pressure within the skull from fluid buildup, a condition known as obstructive hydrocephalus.[6]
Risk Factors
Certain groups of people and specific circumstances increase the likelihood of experiencing altered states of consciousness, particularly those associated with medical conditions. Age is one of the most significant risk factors. Older adults are at substantially higher risk for developing delirium and other forms of altered mental status. This increased vulnerability is partly due to age-related changes in brain function, but also because older individuals are more likely to have multiple medical conditions and take multiple medications that can interact in problematic ways.[9]
People who are hospitalized face elevated risk, especially those admitted to intensive care units or those who undergo major surgery. The stress of surgery, anesthesia, pain, medications, and the unfamiliar hospital environment can all contribute to temporary changes in consciousness. Patients who require mechanical breathing support are at particularly high risk.[9]
Individuals with chronic medical conditions face ongoing risk. Those with diabetes are vulnerable to altered mental status from both very high and very low blood sugar levels. People with chronic kidney disease, liver disease, or heart disease may experience episodes of altered consciousness when these conditions worsen.[6] Anyone with a history of seizures or epilepsy has an increased risk of altered states during seizure episodes.[1]
Substance use and withdrawal represent major risk factors. People who use alcohol heavily, take recreational drugs, or misuse prescription medications are at risk for altered mental status both during intoxication and during withdrawal periods. Even medications prescribed by doctors can cause problems, especially when multiple drugs are taken together or when doses are incorrect.[6]
Sleep deprivation is a risk factor that affects many people. Extended periods without adequate sleep can lead to altered states of consciousness characterized by confusion, poor judgment, and even hallucinations in severe cases.[1] Similarly, severe dehydration or prolonged fasting can alter consciousness, as the brain requires consistent supplies of water and nutrients to function normally.[3]
People with mental health conditions, particularly psychosis, experience altered states as part of their illness. During psychotic episodes, individuals lose touch with reality and may experience disturbing thoughts and perceptions that are not real.[6] Traumatic experiences can also trigger altered states. Severe emotional or physical trauma sometimes leads to dissociative states where consciousness seems to separate from immediate reality as a protective response.[1]
Symptoms
The symptoms of altered states of consciousness vary tremendously depending on the cause and severity. In medical contexts, healthcare providers look for changes in a person’s usual mental functioning, which can manifest in many different ways. One of the most fundamental changes involves alterations in awareness and responsiveness. A person might seem less alert than usual, responding slowly to questions or stimuli, or in severe cases, not responding at all.[6]
Confusion and disorientation are common symptoms. Someone experiencing these symptoms might not know who they are, where they are, what time of day it is, or what year it is. They may have difficulty recognizing familiar people or understanding their current situation. Their thinking may be slow, muddled, or incoherent, and they may struggle to follow simple instructions.[12]
Changes in communication often accompany altered states. Speech may become nonsensical, disorganized, or unusually slow. Some people may repeat the same words or phrases, while others might struggle to find words or construct sentences. In severe cases, speech may be completely absent.[6]
Memory problems frequently occur. Short-term memory is often affected first, with people forgetting conversations that just happened or repeatedly asking the same questions. In some cases, there may be complete memory loss for certain periods, a condition known as amnesia.[6]
Perceptual disturbances can be particularly troubling. Hallucinations—seeing, hearing, feeling, smelling, or tasting things that are not actually present—can occur in various altered states. These might include seeing people or objects that aren’t there, hearing voices, or feeling sensations on the skin. Delusions, which are false beliefs that persist despite evidence to the contrary, may also develop.[6]
Emotional and behavioral changes are common symptoms. A person might become unusually agitated, irritable, or anxious. Conversely, they might withdraw socially and show little interest in their surroundings or other people. Some individuals experience mood swings, shifting rapidly between different emotional states. In some cases, people may display inappropriate behavior or emotional responses that don’t match the situation.[6]
Physical symptoms often accompany the mental changes. These can include fatigue and excessive sleepiness, or conversely, unusual hyperactivity. Some people experience difficulty breathing or shortness of breath. Changes in sleep patterns are common, with some individuals becoming excessively sleepy while others may be unable to sleep at all.[6]
The severity of symptoms exists on a spectrum. At the mild end, someone might be easily distracted and slow to respond but generally aware and able to communicate. This state is sometimes called lethargy. As severity increases, people become more deeply affected. In stupor, a person is in a deep sleep-like state and can only be awakened by loud sounds or painful stimuli, and they quickly fall back asleep when left alone. The most severe form is coma, where a person cannot be awakened at all and makes no purposeful responses to any stimuli.[12]
Prevention
Preventing altered states of consciousness associated with medical conditions involves addressing the underlying risk factors and maintaining overall health. For older adults and hospitalized patients, who face the highest risk of delirium and other acute changes in mental status, several preventive measures have proven effective. These interventions are most successful when multiple strategies are used together through a coordinated team approach.[9]
Maintaining proper hydration and nutrition is fundamental. Dehydration is a common and preventable cause of altered mental status, particularly in older adults who may not feel thirsty even when their bodies need fluids. Ensuring adequate fluid intake throughout the day and eating regular, nutritious meals helps maintain stable blood chemistry and supports brain function.[6]
Sleep hygiene plays an important protective role. Getting adequate, quality sleep on a regular schedule helps prevent the cognitive impairment that comes with sleep deprivation. This means maintaining consistent sleep and wake times, creating a comfortable sleep environment, and avoiding substances that interfere with sleep quality. For hospitalized patients, minimizing nighttime interruptions and maintaining day-night rhythms can help prevent delirium.[9]
Medication management is crucial for prevention. Regular medication reviews with healthcare providers can identify drugs that might increase the risk of altered mental status, especially when multiple medications are taken together. Older adults in particular benefit from periodic assessments of all their medications to ensure each one is still necessary and prescribed at the appropriate dose. Avoiding unnecessary sedatives and sleeping pills reduces risk.[9]
Managing chronic medical conditions effectively helps prevent episodes of altered consciousness. This includes maintaining good control of diabetes to prevent dangerous fluctuations in blood sugar, managing thyroid disorders, treating infections promptly, and monitoring kidney and liver function. Regular check-ups with healthcare providers allow for early detection and treatment of problems before they become severe enough to affect consciousness.[6]
For people at risk of falls and head injuries, environmental modifications can be protective. This includes removing tripping hazards at home, installing grab bars in bathrooms, ensuring adequate lighting, and using assistive devices like canes or walkers when needed. Preventing traumatic brain injuries is important because head trauma can lead to both immediate and delayed changes in consciousness.[6]
Substance use prevention and harm reduction strategies are important for those at risk. This includes avoiding excessive alcohol consumption, not using recreational drugs, taking prescription medications only as directed, and seeking help for substance use disorders. For people with alcohol dependence, medical supervision during withdrawal can prevent dangerous alterations in consciousness that can occur when drinking stops suddenly.[6]
Staying mentally and physically active may offer some protection. Regular physical exercise improves overall health and may help maintain cognitive function. Similarly, engaging in mentally stimulating activities, maintaining social connections, and staying involved in meaningful activities can support brain health. While these measures don’t guarantee prevention, they contribute to overall resilience.[9]
Pathophysiology
The pathophysiology of altered states of consciousness involves understanding how normal brain function becomes disrupted. Consciousness itself arises from the coordinated activity of multiple brain regions, with particular importance placed on the cerebral hemispheres and a structure called the reticular activating system. Damage or dysfunction in either of these areas can lead to altered consciousness.[12]
The reticular activating system, located in the brainstem near where the spinal cord meets the brain, acts as the brain’s arousal center. It sends signals throughout the brain that maintain wakefulness and attention. When this system is damaged by stroke, trauma, or other injuries, the ability to maintain normal consciousness is lost. This is why even small injuries to the brainstem can have dramatic effects on consciousness, while much larger injuries to other brain areas might cause different problems but leave consciousness relatively intact.[12]
Consciousness also depends on having both cerebral hemispheres functioning reasonably well. These are the large, wrinkled surfaces of the brain responsible for higher thinking, perception, and awareness. When both hemispheres are affected by conditions like brain swelling, lack of oxygen, or toxic substances in the blood, consciousness becomes impaired. Interestingly, damage to just one hemisphere typically does not cause loss of consciousness, though it may cause other serious problems.[12]
At the cellular level, brain cells called neurons communicate through electrical signals and chemical messengers called neurotransmitters. Normal consciousness requires this communication system to function smoothly. Many substances that alter consciousness do so by changing the levels or activity of neurotransmitters. For example, sedative medications enhance the activity of neurotransmitters that calm brain activity, while stimulants enhance those that increase activity. Psychoactive substances can dramatically shift these balances, causing changes in awareness and behavior.[3]
The brain requires a constant supply of oxygen and glucose to function. When blood flow to the brain is reduced, whether from heart problems, bleeding, or blocked blood vessels, consciousness quickly becomes impaired. Even a few minutes without adequate oxygen can cause lasting damage. Similarly, when blood sugar levels drop too low, the brain lacks fuel and consciousness is affected. This is why conditions affecting circulation or metabolism so often cause altered mental status.[6]
Metabolic disturbances affect consciousness through multiple mechanisms. When the kidneys or liver fail, toxic substances that would normally be removed from the blood accumulate and poison brain cells. Electrolyte imbalances—abnormal levels of sodium, calcium, or other minerals—disrupt the electrical activity of neurons. Hormonal imbalances, particularly involving the thyroid gland, can slow or speed up brain metabolism in ways that alter consciousness.[6]
Inflammation can also disrupt normal brain function. Infections like meningitis or encephalitis cause inflammation of brain tissue or the membranes surrounding the brain. This inflammatory response, while part of the body’s defense system, can interfere with normal neuronal function and alter consciousness. Even infections elsewhere in the body, particularly in older adults, can trigger inflammatory responses that affect brain function.[6]
Physical trauma affects consciousness through several mechanisms. The immediate impact can cause neurons to stretch, tear, or die. Bleeding into the brain creates pressure that compresses brain tissue and reduces blood flow. Swelling after injury, while a natural response, can be dangerous inside the rigid skull because there is no room for expansion. As pressure builds, critical brain structures can be compressed or pushed out of position, further compromising consciousness.[6]
Recent research into altered states achieved through non-medical means, such as meditation or psychedelics, has proposed interesting theories about brain function. One concept is entropy in brain activity, which essentially measures how flexible or rigid brain patterns are. According to this theory, many mental health problems involve brain activity patterns that are too rigid and inflexible. Experiences that temporarily increase entropy—making the brain more flexible and less bound by its usual patterns—may allow the mind to break free from unhelpful patterns and develop new, healthier ways of thinking and perceiving.[7] This represents an emerging understanding of how therapeutic altered states might work, though much research remains to be done.