The experience of seeing “shadow people”—dark, humanoid figures often glimpsed in the peripheral vision—can be unsettling. These visual hallucinations are linked to several conditions, from sleep deprivation to substance use. One of the most discussed connections is with schizophrenia, a serious mental disorder that affects how a person thinks, feels, and perceives reality.
While shadow people can be a symptom of schizophrenia, they are not exclusive to it. Understanding the link requires looking at how schizophrenia affects the brain and what other conditions can produce similar phenomena.
Hallucinations as a Symptom of Schizophrenia
Hallucinations are a primary symptom of schizophrenia. They are considered a “positive” symptom, which means they are experiences and sensations that are added to a person’s perception of reality. The most common type of hallucination in schizophrenia is auditory, such as hearing voices, which affects a majority of individuals with the disorder.
Visual hallucinations are less frequent but still significant. These can range from seeing flashes of light to fully formed and detailed figures. Shadow people are a recognized form of visual hallucination that can occur in schizophrenia. It is rare for someone with schizophrenia to experience visual hallucinations without also having auditory ones at some point during their illness.
The Brain’s Role in Creating Shadow People
Scientific research points to specific brain activity and chemical imbalances as the source of hallucinations in psychosis. The primary theory involves the neurotransmitter dopamine and the dysfunction of certain brain networks responsible for processing reality.
The Dopamine Hypothesis
The dopamine hypothesis proposes that an excess of dopamine activity in certain pathways of the brain is linked to positive symptoms like hallucinations. This overactivity can cause the brain to misinterpret its own internal thoughts or memories as external sensory information. The brain essentially loses its ability to distinguish between what is real and what is internally generated, leading to a vivid hallucination.
Brain Regions Involved
Visual hallucinations are not random; they are tied to the brain’s visual processing centers. The occipital lobe is the main hub for sight. In people experiencing complex visual hallucinations, higher-order visual cortices—the parts that process complex images like faces and figures—are often active. This activity can cause the brain to “create” an image like a shadow person.
The temporal lobe, which is involved in memory and emotion, also plays a part. Connections between the temporal lobe and the visual cortex can become overactive. This suggests the brain may be drawing on memories and attaching strong emotions to the internally generated images, making the hallucination feel more real and significant.
Other Conditions That Can Cause Similar Hallucinations
Seeing shadow people is not a definitive sign of schizophrenia, as many other conditions can cause similar visual disturbances. It is important to consider these other potential causes for a complete picture.
Other conditions include:
- Sleep deprivation and disorders like insomnia or narcolepsy, especially during the transitions between wakefulness and sleep (hypnagogic and hypnopompic states).
- Substance-induced psychosis, particularly from stimulants like methamphetamine or cocaine, as well as hallucinogens.
- Neurodegenerative diseases such as Parkinson’s disease and Lewy body dementia, which frequently cause complex visual hallucinations.
- High fevers or delirium resulting from a severe illness or infection, which can temporarily alter brain function and perception.