New research finds that having a larger choroid plexus, which is a vital brain structure, could be involved in psychosis.

Variations in the structure of the choroid plexus, which produces cerebrospinal fluid (CSF), could play a key role in psychosis. A team that Dr. Paulo Lizano—of the Beth Israel Deaconess Medical Center in Boston, MA—led has now investigated this vital structure.

In doing so, they found that there could be a link between its size and the development of psychosis. The choroid plexus and its product, CSF, are crucial parts of the neurological system. CSF helps cushion the brain within the skull, and the choroid plexus forms a barrier between the brain and the CSF, which helps filter out toxins and keeps blood components from entering the brain. It also allows some molecules to pass through, including those involved with the immune system.

This study—which now appears in the American Journal of Psychiatry—involved three groups of people: participants with a diagnosis of psychosis, one of their first degree relatives, and people with no history of psychosis (the controls).

Each participant underwent a structural magnetic resonance imaging (MRI) brain scan, and the researchers found that the volume of the choroid plexus was larger in those who had psychosis. They also found that the volume of the choroid plexus among first degree relatives was larger than that of the controls but smaller than that of those with psychosis.

Additional findings

However, these were not the only significant findings from the group with psychosis. The researchers also found that larger choroid plexus volume correlated with reduced gray matter, smaller amygdala volume, lower cognitive scores, larger ventricle volume, and lower levels of neural connectivity.

Although they cannot yet say with certainty, the researchers believe that these findings could also offer clues as to the pathology of psychosis. The team also found that people with an enlarged choroid plexus had high levels of a signaling cell associated with the immune system, called interleukin 6 (IL-6).

IL-6 can cross the barriers between the brain, blood, and CSF. The results are noteworthy; the team explains that people who have schizophrenia and bipolar disorder often have higher levels of IL-6. Dr. Lizano and colleagues conclude:

"Our findings suggest the involvement of the choroid plexus across the psychosis spectrum, with a potential mechanism involving the neuro-immune system, which functions in regulating the brain and interacting with the body's immune and inflammatory systems."

What is psychosis?

According to the National Institute of Mental Health, psychosis refers to a group of conditions that affect the mind when someone experiences a "loss of contact with reality." During a psychotic episode, a person's thoughts and perceptions are disturbed. They may find it difficult to understand what is real and what is not. Some symptoms of psychosis include:

• Delusions, or false beliefs
• Hallucinations, such as seeing or hearing things that others do not
• Incoherent speech
• Inappropriate behavior

Experts say that there is no single cause of psychosis. It can be a symptom of a mental health condition such as schizophrenia. There are also several other potential causes, including some medical conditions, drug and alcohol use, certain prescription medications, and sleep deprivation.

There were some scientific discussions in the 1920s about the possible role of the choroid plexus in schizophrenia or bipolar disorder. However, there had not been much specific research on the topic before this study. Although much more research is still necessary, this study suggests that there is probably a link between an enlarged choroid plexus and psychosis.