The sex-hormones testosterone and oestrogen are implicated in psychological behaviour and as such, also in psychiatric disorders. Specifically, the sex-hormones, testosterone and oestrogen are implicated in mood and mental health stability. An increase in testosterone and oestrogen accompany physical and psychological changes during puberty and the age at which this begins may vary from aged 10 to 15 for girls and aged 11 to 16 for boys, rising gradually until reaching a peak just after adulthood. If children have indications of early higher levels of sex hormones through signs of early puberty, the associative link with later-life adult mental health and cognition would be difficult to assess unless a longitudinal birth cohort study was conducted. By using existing population cohorts with retrospective proxy measures of early childhood hormonal proxy indicators, this study will explore an extrapolated childhood hormone level, adult mental health, adult hormone level and cognitive performance to investigate the associations and interactions between these variables whilst controlling for co-variates such as social deprivation, age and medications. The main aim of the study therefore is to utilise the power of DPUK cohorts to assess early-life predictors and, interactions of the sex-hormones, mental health and cognition.