Most individuals have some degree of impulsivity and compulsivity. However, exacerbation of these traits is linked to a number of maladaptive behavioural styles and psychiatric illnesses. For example, impulsive traits (e.g., acting without appropriate forethought) have been classically linked to both impulse control disorders (eg, addictions), whereas compulsive behaviours (e.g., persisting with inappropriate behaviours despite negative outcomes) represent a cardinal symptom of obsessive compulsive disorder (OCD). Whilst impulsive and compulsive traits have been historically linked to unique disorder subtypes, there is evidence of strong overlap of both impulsive and compulsive behaviours across different a spectrum of mental disorders, including substance misuse, pathological gambling, and OCD. However, there is currently little understanding of how, or why, impulsive and compulsive behaviours co-occur. As such, there is an urgent need to determine how impulsive and compulsive traits are related and dissociable, and to what extent the unique and shared variation in these traits drive maladaptive behaviours and sub-threshold psychiatric symptoms in the general population. This approach would therefore represent the most cutting-edge conceptualisation of these traits, and may assist in the development of intervention strategies that target specific symptoms of the disorders for which dysregulated impulsivity and compulsivity are core features.
Whilst there is strong evidence that family history is a strong predictor of both impulsive and compulsive behaviours, the unique and shared heritability of these traits remains to be elucidated. In this research study, we will examine impulsive and compulsive (i.e., cognitive and behavioural) traits in a normative population of Australian twin siblings in collaboration with Twins Research Australia, which will offer a unique opportunity of estimating the heritability, comorbidity, and influence of shared and non-shared environmental factors on the prevalence of impulsive and compulsive traits. No such population-based twin study has thus far attempted to disentangle these relationships, and the proposed study will therefore provide an important opportunity to characterise common and unique genetic liabilities for impulsive and compulsive behaviours.