Why Your Brain Sometimes Plays Tricks on You ?
– Rami Hamati –
Paranoia is far more common than we think and a tiny part of the brain may explain why. In a recent study conducted at the Institute of Mental Health Research in Ottawa, we used a specialized brain scan to measure the dopamine activity in the brain. We found that the more active someone’s dopamine system had been over their lifetime, the more often they experienced paranoid thoughts. This shows us that paranoia is not a switch; it’s a spectrum that can affect all of us.
Most of us have experienced that sudden, eerie sensation of being watched or the unsettling suspicion that a stranger’s laughter was directed at us. That feeling is named paranoia, and it’s far more common than you might think.
Almost one in ten people experience it regularly without it ever becoming an issue in daily life. In fact, paranoia exists on a spectrum, from fleeting suspicion to full-blown delusion. The difference between the two, may be explained by a brain chemical usually associated with pleasure and reward: dopamine. So what happens in the brain when we feel like we’re being watched?
The chemical behind the story
By trying to reply to this question, we discovered for the first time that participants who experience paranoid thoughts more often have a stronger dopamine signal in the brain.
Dopamine isn’t just a pleasure chemical that is produced in your body when you eat your favorite meal or you buy something at the mall. It’s a signal that tells the brain to pay attention to something important. Even if the dopamine is hiding in our brain, we can capture a snapshot of the system at one point in time and measure it. However, we used a different method for our study. We look at the brain’s past activity, not just its present with a very special brain scan called NM-MRI.
Here’s how it works. Every time a brain neuron produces dopamine, it leaves behind a tiny dark trace, like a fingerprint. Over years, these traces pile up, and the more active your dopamine system has been, the more of this pigment builds in the brain. This is what makes the scan so useful. A normal brain scan for dopamine only shows what’s happening right now, like a photo taken at the moment. However, our technique allows us to look back at everything your brain has been doing for years without needing surgery or injections.
Participants that joined our study also completed a questionnaire about their own paranoid thoughts by replying to three simple questions: How often did they occur? How strongly were they believed? How much distress did they cause? This is what let us test whether the dark trace signal was linked to how someone experienced paranoia. In the meantime, we wanted to control their family history for an interesting reason.
Does paranoia run in families?
Previous studies have shown that siblings and children of people with psychiatric disorders face a higher risk of developing the disorder themselves and may also show too much dopamine activity. To see if dopamine is also different in the family members of psychiatric disorders, we compared two groups: participants with a family member affected by psychosis, and participants without one.
Surprisingly, we found no difference between the two groups which suggests that our dopamine history isn’t simply written into our genes, but rather a combination of both genetic and environmental factors, like stress that could also contribute to high dopamine levels.
Interestingly, this signal tracked how often these paranoid thoughts occurred, but not the level of distress or conviction they caused. This suggests that while an overactive dopamine system might be the engine generating these thoughts, other brain chemicals likely work alongside dopamine to determine whether we actually believe those thoughts or find them upsetting.
When dopamine neurons are overactive, the brain starts flagging ordinary moments as suspicious, like a stranger’s laugh. Things that are probably innocent feel like they mean something. Now that we’ve established why dopamine is important, and how we can track its history, some questions still remain.
Other pieces of the puzzle to look at
Our findings reveal dopamine helps make paranoid thoughts, but not how much we believe them or how much it upsets us. If high dopamine activity makes us prone to paranoia but doesn’t guarantee illness, what is the “tipping point”?
That gap between having a paranoid thought and being distressed by it may be the key to understanding how a healthy brain response can slowly turn into something more serious. Other brain chemicals likely play a role too, and studying how they interact with dopamine is exactly where the research is heading next.
Discover the original scientific article
SN/VTA neuromelanin signal is associated with subclinical paranoia irrespective of familial risk for psychosis
Schizophrenia (Heidelb), 2026
Discover the author
Dr. Rami Hamati is a postdoctoral associate at Western University. His research focuses on how brain chemicals may lead to mental health symptoms.
Glossary
Dopamine: Biological indicators found in the body that can provide researchers with information about how the body is functioning. For example, certain biomarkers can provide information about stress or other biological processes.
NM-MRI: A brain scan that measures dopamine “fingerprints” to reveal a person’s long-term dopamine activity over years
Paranoia: a mental state where a person often believes that people are trying to cheat, harm, or deceive them, even when there is no proof
Editing and revision of the popular science article :
Aurore Lebourg, Scientific Communication Coordinator