Personality traits such as extraversion and neuroticism are associated with mental health and well-being with trait extraversion positively associated with resilience, and negatively associated with a plethora of mental disorders including depression. Resilience was likely a useful trait during the COVID-19 pandemic which studies have shown negatively impacted the mental health of several different population groups, particularly university students. Mental health may also have been impacted differentially based on trait extraversion, with some evidence finding the mental health of extraverts was negatively impacted by lockdown. This review aimed to investigate whether trait extraversion was protective to university student mental health and well-being, operationalised by different symptom domains including stress and anxiety, during lockdown. We hypothesised that due to an extravert's proclivity to seek out and enjoy social interaction and the restriction of these very activities during lockdown, trait extraversion would no longer have a protective effect on mental health and well-being.

Six databases (EMBASE, MEDLINE, PSYCHINFO, SCOPUS, Web of Science and Cardiff University Full Text Journals) were consulted, and forty-five studies identified. Briefly, the eligibility criteria were studies of university students that had trait extraversion measured using either the Big Five or Eysenck's Personality Questionnaire in addition to a measure of mental health or well-being. Furthermore, at least 50% of the study must have been conducted under lockdown conditions with cross-sectional and longitudinal studies eligible for inclusion. After data screening, three longitudinal and seven cross-sectional studies were identified as eligible for inclusion. Following data extraction, a qualitative narrative synthesis was applied to the extracted data.

Significant results were found for positive affect, negative affect, life satisfaction, quality of life enjoyment and satisfaction, anxiety and depression which suggested extraversion was protective. Non-significant results were also found for anxiety, depression, mental health, global quality of life, perceived stress, COVID-19 student stress and coronavirus anxiety.

The hypothesis that extraversion would be protective for mental health and well-being was accepted unanimously for life satisfaction and tentatively for anxiety. Furthermore, the hypothesis was rejected for depression and stress whose relationship with trait extraversion differed from pre-pandemic findings. The review recommended that extraverted university students should be mindful of the increased risk of depression and stress during lockdown. Additionally, further research should be carried out on extraversion's relationship with stress, an important factor in mental health, and also look at interactions of trait extraversion with other personality traits such as neuroticism.