This project is a continuation of research previously carried out using data from the National Survey of Sexual Attitudes and Lifestyles (Natsal) 2000. This research identified statistically significant associations between early sexual debut and risky or non-normative sexual behaviour later into adulthood (aged up to 29). Those respondents whose sexual debut occurred before the age of 16 had increased odds of engaging in certain risky or non-normative sexual activities later in life. This association maintained significance with the addition of potential confounders. This PhD aims to explore this phenomenon further.

An essential component of this research is to identity what factors influence contemporary young persons' engagement in sexual activities early on in life. While existing research provides evidence of socio-psychological and economic predictors (ranging from personality type, to family structure, parenting and enjoyment of school) such research in Britain is limited, particularly that of a longitudinal nature examining the multitude of influences which may cause, interact and feedback on one another. The majority of British studies in this topic area rely on cross-sectional data and concentrate on only a few predictors. Given the older age and the subject coverage of the British birth cohorts, longitudinal data with the potential to examine contemporary teenagers' trajectories into their sexual live is essentially non-existent, with the exception of the ALSPAC cohort.

Analyses will be carried out separately for males and females, so allowing identification of gender differences. Rather than stopping at the identification risk factors, further structural equation modelling and pathway analysis will be carried out in an effort to identify mediating factors. The longitudinal nature of the data lends itself particularly well to pathway analysis; once theoretical mediators are identified from the literature they can be analysed in chronological order.

In addition to the focus on age at sexual debut, this project also seeks to explore the concept of 'sexual competence' as defined by Wellings et al., 2001 as a sexual encounter characterised by the absence of duress and regret, autonomy of decision, and use of a reliable method of contraception. A similar composite measure as that used by Wellings et al can be constructed using ALSPAC data. This measure will undergo critical review in order to establish its validity before it is included in final analyses. Latent class analysis of sexual competence at each time point when the 'Romantic Relations' questions were completed will allow the exploration of how sexual competence changes or develops over time; this will of course be limited by how many people have actually begun engaging in sexual activity at a young age and will be subject to censoring. Using latent class analysis in this way will allow the identification of distinct trajectories of sexual competence, which can then be analysed against the relevant predictors.

Attention will also be paid to other 'risky' behaviours, such as smoking, alcohol consumption and drug use alongside sexual behaviour. The clustering of a variety of risk behaviours within certain individuals has been reported previously. The record of these behaviours in the ALSPAC cohort at different ages lends itself well for the exploration of behavioural trajectories; examining the temporal relationship between smoking, alcohol consumption, drug use and sexual activities in adolescence.

This project would seek to use the breadth of data available in ALSPAC which pertains to the influences on development of the children under study. Broadly, this would include family factors (such as structure, social support and parenting), school factors (such as school ethos, support from teachers, enjoyment of school, aspirations), personality measures (such as impulsivity, sensation-seeking and locus of control), peer and friendship factors and other risk behaviours (such as smoking, alcohol, drugs). The availability of such measures at different points throughout the life course is hugely valuable for establishing temporality, in addition to identifying whether the effect of such influences differ according to the age at which the child was exposed to them.