A systematic review of state loneliness in daily life using intensive longitudinal methods.

In 30 seconds

This PRISMA systematic review synthesised 117 studies using intensive longitudinal methods, including ecological momentary assessment, experience sampling and daily diaries, to examine state loneliness across age groups. It reviewed how loneliness was measured, factors associated with momentary loneliness, and links with mental health and well-being. State loneliness was usually measured with a single item, while empirical evidence on measurement properties was rarely reported. Associations were found with mental health outcomes, including internalising symptoms and suicidality, and with social interaction; some studies reported relationships in both directions, varying by design and analytic approach.

Key findings

• The review included 117 studies of state loneliness assessed using intensive longitudinal methods.
• State loneliness was predominantly measured with single items and varied response formats; empirical psychometric evidence was rarely reported.
• State loneliness was associated with mental health outcomes, including internalising symptoms and suicidality, and with social interaction.
• Physical health, age and gender were also linked to state loneliness.

Why it matters

Moment-to-moment loneliness may relate to mental health and social interaction in ways that chronic-loneliness research does not capture. The review highlights both the potential value of intensive longitudinal assessment for understanding these links and a measurement gap: commonly used single-item measures often lack reported empirical psychometric evidence. These findings can inform future research on when loneliness occurs and how it relates to well-being.

What to keep in mind

The review reports that empirical psychometric evidence for the commonly used loneliness items was rarely available. Associations varied with study design and analytic approach, limiting uniform interpretation.