Why do people feel like they're being watched, even when no one is there?

You're alone, and you suddenly have the sneaking suspicion that someone's there. Maybe you watched a scary movie or read the latest thriller novel and wonder if there's a killer lurking in your room. You look around and open the closet door, but no one's there. So why does your mind make you feel as if you were being watched?

According to Leslie Dobson, a clinical and forensic psychologist, there are a number of reasons why someone may feel as if they are being watched. These causes span a broad spectrum, including exposure to scary books, movies or news; hypervigilance following a stressful or traumatic event; and serious mental health conditions.

"In more extreme cases, a person may experience paranoia and hypervigilance, often related to an underlying mental health condition or physical brain ailment," Dobson said in a written message.

Of course, sometimes we really are being watched. People likely evolved to be sensitive to another person's gaze, and it's been suggested the human brain has a neural network dedicated solely to processing gaze, according to an article written by Harriet Dempsey-Jones, a postdoctoral research fellow in cognitive neurosciences at The University of Queensland in Australia. It's possible that our attentiveness to gaze arose because it can support cooperative interactions between humans. This ability usually isn't difficult to master; it's fairly easy to see where a person is looking because we can see where their pupils are focused, and with our peripheral vision we can pick on cues, such as body language, indicating that a person is looking at us.

But sometimes, even if no one is watching, outside stimuli can make us feel afraid and look around to see if we're being watched. This could include watching or reading a thriller in which a protagonist is being stalked by a threatening figure, or hearing a random noise when home alone.

Related: Why do people dissociate during traumatic events?

For people who have experienced traumatic events, hypervigilance becomes a defense mechanism that is meant to prevent us from experiencing future stress by avoiding danger, according to a 2023 study in the journal Frontiers in Psychology. Symptoms like paranoia and anxiety that usually come after stressful events can occur in a similar region of the brain, Dobson explained.

"The amygdala processes our emotions such as stress and anxiety," she told Live Science. "If it is overactive or harmed from physical damage or ongoing trauma stressors, it may lead to heightened emotional responses such as perceiving threat."

It's not uncommon for people to feel watched, Dr. Alice Feller, a clinical psychiatrist based in California, told Live Science. So how do you distinguish reasonable caution from a more serious issue?

The problem arises when someone constantly feels watched or paranoid about being watched for a long period of time.

"[With] mental illness, what happens is you lose that ability to wonder if it's just a feeling, you know, you kind of lose insight into your own bodily and mental process," Feller said. "You can do a reality check, but it doesn't necessarily stick."

For example, symptoms of schizophrenia include hypervigilance and paranoia, which can include the delusion that someone is watching you. Research suggests that in people with schizophrenia, paranoia is associated with abnormal activity in the limbic system, a part of the brain that includes the amygdala and controls our emotional and survival-based behavioral responses, such as the fight-or-flight response.

A 2022 study explained that in patients with schizophrenia, paranoia has been associated with increased blood flow during resting state in the amygdala. Moreover, unusual connectivity between the amygdala and other areas of the brain, such as the visual cortex, hippocampus and the prefrontal cortex, has been linked with paranoia, suggesting that "current paranoia is linked to aberrant connectivity within the core limbic circuit" suggesting "amplified threat processing and impaired emotion regulation."

Regardless of the cause, Feller and Dobson both said that it's worth seeking mental health support if you experience persistent paranoia. This is especially true if the feeling of being watched happens despite physical evidence that no one else is there, or if the anxiety of being watched becomes worse.

"I encourage people to seek mental and medical intervention when they begin to notice they are struggling, rather than trying to wait it out," Dobson said. "Early intervention is key. If a person is struggling more days a week than not, or if their job, education, or relationships are beginning to struggle, it is important to seek out a professional."

This article is for informational purposes only and is not meant to offer medical advice.