Illustration of an adolescent brain highlighting asymmetric subcortical regions.

Brain Asymmetry and Mental Health: What Early Brain Scans Reveal About Psychotic Experiences

Kai Mendoza in Mind & Education August 2025 • 4 min read.

"New research uncovers how subtle differences in brain structure during adolescence might offer clues to future mental health challenges, sparking new avenues for early intervention and support."

Mental health disorders, particularly those involving psychosis, are complex and often devastating. Scientists have long sought to understand the biological underpinnings of these conditions, hoping to identify early markers that could allow for timely intervention. A recent study published in 'Translational Psychiatry' sheds new light on this area by exploring the relationship between brain structure and subclinical psychotic experiences (SPEs) in adolescents.

SPEs are experiences that resemble psychotic symptoms, such as hallucinations or delusions, but are less severe and don't meet the criteria for a full-blown psychotic disorder. These experiences are not uncommon in adolescence, with some studies estimating that up to 5% of young people may experience them. While many individuals who report SPEs do not go on to develop psychosis, they are at an increased risk, making the identification of potential biological markers crucial.

The study, led by researchers at the University of Tokyo, investigated whether differences in the volumes of subcortical brain regions are associated with SPEs in a large sample of adolescents. Subcortical structures, including the basal ganglia and limbic system, play critical roles in various functions, including learning, emotion, motor control, and higher-order cognitive processes. Previous research has suggested that alterations in these regions may be linked to schizophrenia and other psychotic disorders.

Unveiling the Adolescent Brain: What the Study Showed

Illustration of an adolescent brain highlighting asymmetric subcortical regions.

The researchers used magnetic resonance imaging (MRI) to measure the volumes of subcortical brain structures in 203 adolescents aged 10.5 to 13.3 years. These participants were part of a larger population-based cohort study called the Tokyo TEEN Cohort (TTC). The adolescents also completed a screening questionnaire to assess their experiences with SPEs.

The study's findings revealed several significant associations between brain volume and SPEs. Adolescents with SPEs had larger volumes in the left hippocampus, right caudate, and right lateral ventricle compared to those without SPEs. They also found a marginally significant increase in the left pallidum.

Left Hippocampus: This brain area is vital for memory and learning.
Right Caudate: Part of the basal ganglia, involved in motor control and cognitive functions.
Right Lateral Ventricle: A fluid-filled space in the brain; increased volume may indicate various neurological conditions.
Left Pallidum: Another component of the basal ganglia, important for motor control.

Perhaps most interestingly, the researchers found that adolescents with SPEs showed significantly more leftward laterality of pallidal volume than those without SPEs. This means that the left pallidum was larger than the right pallidum in individuals with SPEs, a pattern that mirrors findings in adults with chronic schizophrenia. This discovery suggests that altered pallidal asymmetry may be a premorbid characteristic, potentially indicating a predisposition to developing psychosis later in life.

What Does This Mean for the Future of Mental Health?

This research offers valuable insights into the early neurobiological underpinnings of psychotic experiences. By identifying potential markers like altered pallidal asymmetry, scientists may be able to develop more effective strategies for early identification and intervention. Further research is needed to fully understand the role of these brain differences and how they may interact with genetic and environmental factors. However, this study represents an important step forward in our quest to unravel the complexities of mental illness and improve the lives of those at risk.

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This article is based on research published under:

DOI-LINK: 10.1038/s41398-018-0312-6, Alternate LINK

Title: Abnormal Asymmetries In Subcortical Brain Volume In Early Adolescents With Subclinical Psychotic Experiences

Subject: Biological Psychiatry

Journal: Translational Psychiatry

Publisher: Springer Science and Business Media LLC

Authors: Naohiro Okada, Noriaki Yahata, Daisuke Koshiyama, Kentaro Morita, Kingo Sawada, Sho Kanata, Shinya Fujikawa, Noriko Sugimoto, Rie Toriyama, Mio Masaoka, Shinsuke Koike, Tsuyoshi Araki, Yukiko Kano, Kaori Endo, Syudo Yamasaki, Shuntaro Ando, Atsushi Nishida, Mariko Hiraiwa-Hasegawa, Kiyoto Kasai

Published: 2018-11-28

Everything You Need To Know

What are Subclinical Psychotic Experiences (SPEs), and why are they important to study?

Subclinical Psychotic Experiences (SPEs) are experiences that resemble psychotic symptoms like hallucinations or delusions, but are less severe and don't meet the criteria for a full-blown psychotic disorder. SPEs are significant because, while many adolescents who experience them do not develop psychosis, they are at an increased risk. Identifying biological markers associated with SPEs could allow for timely interventions.

How did the study measure brain structure, and what specific brain regions were examined?

The study used magnetic resonance imaging (MRI) to measure the volumes of subcortical brain structures in adolescents. The specific subcortical structures examined were the left hippocampus, right caudate, right lateral ventricle, and left pallidum. These structures were chosen because they play critical roles in functions like learning, emotion, motor control, and higher-order cognitive processes, and previous research has linked alterations in these regions to schizophrenia and other psychotic disorders.

What did the study discover about the brains of adolescents who experience Subclinical Psychotic Experiences (SPEs)?

The study found that adolescents with Subclinical Psychotic Experiences (SPEs) had larger volumes in the left hippocampus, right caudate, and right lateral ventricle compared to those without SPEs. A marginally significant increase was also found in the left pallidum. Most notably, adolescents with SPEs showed more leftward laterality of pallidal volume, meaning the left pallidum was larger than the right. This finding is significant because altered pallidal asymmetry has also been observed in adults with chronic schizophrenia, suggesting it may be a premorbid characteristic indicating a predisposition to developing psychosis.

What are the hippocampus, caudate, lateral ventricle, and pallidum, and what do they do?

The hippocampus, caudate, lateral ventricle, and pallidum are all subcortical brain structures. The left hippocampus is crucial for memory and learning. The right caudate, part of the basal ganglia, is involved in motor control and cognitive functions. The right lateral ventricle is a fluid-filled space; increased volume may indicate various neurological conditions. The left pallidum, another component of the basal ganglia, is important for motor control. Variations in the size or asymmetry of these structures may be linked to mental health conditions.

Why is altered pallidal asymmetry considered a potentially important finding?

Altered pallidal asymmetry, where the left pallidum is larger than the right, is significant because this pattern has been observed in both adolescents with Subclinical Psychotic Experiences (SPEs) and adults with chronic schizophrenia. This suggests that altered pallidal asymmetry may be a premorbid characteristic, potentially indicating a predisposition to developing psychosis later in life. Identifying such markers early could allow for interventions to mitigate the risk of developing full-blown psychotic disorders.