Common genetic variants in the oxytocin receptor gene (OXTR) have previously been associated with social behaviours, personality and mood (Li et al., 2015; Saphire-Bernstein et al., 2011). Emerging evidence has demonstrated that genetic variants such as rs53576 and rs2254298 may play a role in social behaviour and interpersonal relationships, with individuals carrying homozygote G alleles having greater sociality compared to those carrying A alleles (Li et al., 2015). These individuals are also reported to have higher empathy and higher sensitivity to social cues (Connelly et al., 2014). There is also evidence to suggest that variation in OXTR is also associated with lower symptoms of depression and anxiety (Brune, 2012; Saphire-Bernstein et al., 2011). More recently, evidence has shown an association between OXTR variants and pathways to addictive behaviour such as alcohol and drug misuse, via an interaction with early environmental stressors (Buisman-Pijlman et al., 2014). Research in this area may uncover mechanisms underlying addiction and poor mental health. Identifying these mechanisms is crucial for improving and developing new treatments for these disorders.

Despite evidence linking OXTR with mood, personality and social behaviour, some of this research shows small effect sizes or contrasting results. For instance, a meta-analysis by Bakermans-Kranenburg and van Ijzendoorn, (2014) failed to find any association between rs53576 polymorphisms and sociality. However, a follow up meta-analysis by Li et al., (2015) found the opposite with modest effect sizes between this SNP and sociality.

One possible reason for contrasting findings could be the role of the environment and this interaction between the genetics and early environmental exposures. It has been established that early environmental factors play a role in developmental pathways (Buisman-Pijlman et al., 2014; Stingaris et al., 2014), yet not all research considers environmental factors playing a role in later mental health outcomes. Research exploring the role of the 5-HTTLPR genotype alluded to the importance of early life stressors and maternal depression on later childhood symptomology (Araya et al., 2008). Consequently, the role of the early environment must be explored when examining causes for maladaptive developmental pathways. A further point is that many of the studies use very small sample sizes that often fail to detect any of these complex and important effects. To further clarify the role of OXTR in personality, mood, social behaviour and addiction, research has to maximise all available output. Using from data from cohort studies provides a rich background of data and allows researchers to examine developmental pathways from an epidemiological approach, rather than opportunity sampling. Another bonus is that using cohort data allows for increased sample sizes that can help determine true effects. Using both phenotypic and genetic data from the ALSPAC study, this project will examine the association between OXTR and mood, personality characteristics, sociality and addictive behaviours. By using the ALSPAC database, this project can examine any interactions between genetics and early environmental factors (e.g., early life stress, parenting styles, socioeconomic status and parental depression) with these outcomes.