Summer 2023 Research Roundup

In this quarterly Research Roundup, we provide an overview of some recent research into the adolescent years, showcasing the interactions between adolescent brain development and our environments, social connections, and sense of identity.

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In This Roundup

Environments & Brain Development

• Brain systems involved in learning and emotional development grow and change in response to the socioeconomic environment in adolescence
• State-level anti-poverty programs can help reduce the negative effects of socioeconomic disparities in brain development and mental health in early adolescence
• Stressful environments are linked to more impulsive behavior during adolescence due to their detrimental effects on sleep

Relationships & Social Connection

• Social connectedness in early adolescence is associated with structural connectivity within the brain
• High acceptance from parents can protect against mental health problems in adolescence related to earlier puberty

Identity Development

• Prefrontal cortex activity during self-evaluation peaks in adolescence and contributes to identity development

Research

Environments & Brain Development

Brain systems involved in learning and emotional development grow and change in response to the socioeconomic environment in adolescence

In a study of 1,033 youth ages 8 to 23, Valerie Sydnor and colleagues assessed the development of neural plasticity–our brains’ ability to grow and change in response to our experiences–by tracking changes in brain activity across ages as well as the influence of youths’ neighborhood socioeconomic environment. Results showed that the plasticity of brain systems involved in learning and emotional development peaked around 15 years old and declined from there, suggesting a sensitive period during which our brains are primed for adapting and changing in response to our environment. The effects of the socioeconomic environment on brain function also peaked in mid-adolescence and were strongest in areas such as the prefrontal cortex, indicating that the regions that showed greater plasticity in adolescence were also those most susceptible to environmental influence. (Nature, March 2023)

Why this is important: By showing that brain systems involved in learning and emotional development are sensitive to environmental influence in adolescence, this paper highlights the opportunity for targeted interventions focused on enriching the neighborhood environment, such as by increasing access to physical and educational resources, to be especially effective during this developmental period.

State-level anti-poverty programs can help reduce the negative effects of socioeconomic disparities in brain development and mental health in early adolescence

In this study, David Weissman and colleagues explored associations between socioeconomic status, brain development, and internalizing symptoms (such as anxiety and depression) in a sample of 10,000+ youth ages 9 to 11 living across 17 different states. Youth with lower family income showed smaller volumes of the hippocampus, a region important for learning and memory, as well as higher levels of internalizing symptoms, particularly for those young people living in states with a high cost of living. However, in high-cost-of-living states that provided more generous benefits for low-income families, the differences in hippocampal volumes and mental health issues were reduced, with more generous cash benefits lessening the associations between low income and brain and behavioral effects. (Nature, May 2023)

Why this is important: This paper suggests that state-level anti-poverty programs aimed at aiding and protecting adolescents in low-income families can reduce the negative effects of socioeconomic disparities in brain development and mental health in adolescents.

Stressful environments are linked to more impulsive behavior during adolescence due to their detrimental effects on sleep

In a sample of 11,000+ youth (ages 9 to 11 at baseline) assessed over three time points, Linhao Zhang and colleagues tested whether sleep problems explained the link between stressful environments and later impulsivity. They also tested how connectivity in the default mode network (DMN) of the brain (involved in behavioral control, stress regulation, and sleep patterns in adolescents) affected this link. Stressful environments were shown to be related to later higher impulsivity largely due to their impact on adolescent sleep. Further, youth who began the study with greater connectivity within the DMN showed a stronger link between sleep duration and later impulsivity, suggesting that heightened within-DMN connectivity may be a risk factor for sleep-related effects on impulsivity later in adolescence. (Sleep Health, June 2023)

Why this is important: These findings suggest that lack of sleep may explain the link between stressful environments and increased impulsivity in adolescence, highlighting the potential of sleep interventions to support healthy behavioral development.

Relationships & Social Connection

Social connectedness in early adolescence is associated with structural connectivity in the brain

In this study of 73 12-year-olds, Christina Driver and colleagues explored how social connectedness—an adolescent’s sense of closeness to and belonging with others—is reflected in structural connectivity of the brain as measured through white matter, the network of fibers that allow the exchange of information between brain regions. Young people who were more socially connected showed greater brain connectivity across numerous long-range white matter pathways. Youth who reported less social connectedness showed less structural connectivity. Other factors, including gender and levels of psychological distress, did not appear to affect the relationships between social connectedness and structural connectivity in the brain. (Behavioral Brain Research, February 2023)

Why this is important: This study highlights the importance of social connectedness for brain and behavioral functioning in adolescence.

Acceptance from parents can protect against mental health problems in adolescence related to earlier puberty

In this study, Nandita Vijayakumar and colleagues examined the connection between early pubertal timing and mental health problems by looking at connections between brain regions involved in emotional reactivity and regulation (called “corticolimbic connectivity”). In a sample of 10,000+ children and adolescents ages 9 to 14 , the authors found that youth who underwent puberty earlier than their peers showed less connectivity between the limbic system–involved in processing basic emotions–and a range of other brain networks, partly explaining the link between earlier pubertal timing and symptoms of depression. Importantly, the study also found that youth who experience higher levels of acceptance from their parents were less likely to experience these changes in corticolimbic connectivity, suggesting that a positive family environment can reduce the negative effects of earlier pubertal timing. (Psychological Medicine, June 2023)

Why this is important: This study suggests how early pubertal timing may lead to mental health problems and highlights the potential for positive family environments to help protect against these problems.

Identity Development

Prefrontal cortex activity during self-evaluation in adolescence contributes to identity development

In this longitudinal study of 189 10- to 24-year-olds, Renske van der Cruijsen and colleagues examined how youths’ own opinions of themselves, what they believed their peers thought about them, and related activity in the brain changes over adolescence. Youth evaluated themselves in the areas of academics, physical appearance, and prosocial behavior (such as helping others) from their own and their peers’ perspectives while undergoing a brain scan across three time points. In the brain, activity of the medial prefrontal cortex (mPFC)—a crucial region for self-identity—was more responsive to self-evaluation than to perceived peers’ opinions, peaking in mid-to-late adolescence and leveling out in young adulthood. Activity in the temporal parietal junction (TPJ)—an important region for understanding the mental state of oneself or others—was stronger for perceived peers’ evaluations, and increased by age. Youth with more positive self-evaluations showed more stable self-concept and less fear of negative evaluation by others one to two years later. (Social Cognitive and Affective Neuroscience, January 2023)

Why this is important: This study shows that brain regions involved in self-identity are especially sensitive to self-evaluation in adolescence and highlights the importance of developing positive self-concept during this window of development.