Non-clinical individuals with subsyndromal hypomanic experiences have been shown to be at a heightened risk for developing BD and have been linked to similar severity and impairment experienced by people with BD. A better understanding of the characterisation of hypomania in young people may help improve accurate and timely diagnosis of BD. Despite its potential importance, limited research is available concerning the structure of hypomania among non-clinical young people, particularly in the UK. Therefore, the current study will explore the structure and characterisation of hypomania in a British nonclinical cohort. We propose to examine the distribution and underlying structure of components of hypomania in ALSPAC, along with measure of different psychological and psychopathological dimensions and investigate hypomania symptoms’ association with other psychopathological variables (e.g., substance abuse). Using confirmatory factor analysis and latent class analysis, this study may help explore the structure and characterisation of hypomania in young people. Better understanding of hypomania could provide opportunities for targeted intervention and prevention.