Millennium Cohort Study Longitudinal Files User Guide

This guide provides information about the mcs_longitudinal_family_file which is an important dataset of the Millennium Cohort Study (MCS). A new longitudinal cohort member file, named mcs_longitudinal_cm_file, has been introduced at individual cohort member level following the MCS data collection at age 23 (sweep 8) and is included in this version.

Version 3 updated: February 2026.