Being Alone: Social Disconnection in Adolescence

Social isolation and loneliness are increasingly prevalent worldwide, with individuals aged 16-24 years reporting particularly high levels. This vulnerability during a sensitive window of social and emotional development is concerning given that loneliness strongly predicts mental and physical health outcomes. Despite being one of the loneliest age groups, adolescents report higher social media use than any other demographic. However, the relationship between digital social interactions and loneliness is unclear. While digital social interactions might displace some face-to-face communication, they can also strengthen existing relationships and foster new connections. This thesis investigates social isolation and digital social connection in adolescents, and is divided into two parts. Part one employs an experimental paradigm to examine the effects of short-term social isolation on human adolescents aged 16-19 years. Using a within-participant design, adolescents underwent baseline testing and sessions of complete isolation and isolation with digital social interactions. Chapter two investigates the effects of social isolation on psychological state and on threat learning. Chapter three investigates the effects of social isolation on reward responsiveness — including reward seeking and reward learning — integrating computational models of learning. Chapter four leverages ultra-high field 7-Tesla MRI to identify neural predictors of sensitivity to isolation. Part two uses non-experimental methods: chapter five systematically reviews adolescent online and offline self-disclosure, examining whether and how digital social connections fulfil social needs; chapter six examines late adolescents' digital social interactions and loneliness amid social distancing during COVID-19; and chapter seven explores emotional experiences and mental health changes in young people facing social disconnection. The findings advance our understanding of how social isolation impacts adolescent mental health, bridging human and animal research while highlighting both opportunities and limitations of digital social connections. This work has implications for supporting healthy development and reducing adolescent loneliness in an increasingly online world.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Towner, Emily

Advisor dc:contributor.advisor

• Blakemore, Sarah-Jayne

• adolescence
• loneliness
• reward
• social isolation
• threat

Licence

• https://www.repository.cam.ac.uk/bitstreams/b07dfea3-aa9a-48b8-81f0-daaa2f7a8444/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.122322

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/391036