Genetics Basis of Impulsivity: The Role Serotoninergic and Dopaminergic Genes

The aim of the present chapter is to summarize the current knowledge of genetic basis of impulsive behaviours, which occur across several neuropsychiatric disorders. Impulsivity most frequently characterizes attention-deficit/hyperactivity disorder, substance abuse, binge eating, personality disorders, suicidal behavior, with important ramifications for everyday functioning and quality of life. The existence of a genetic component and inheritance of impulsivity has been largely demonstrated in families and twins studies. Moreover, in the last years, molecular genetic studies have been considerably increased, reporting several positive associations between genetic variants and impulsivity, particularly as regard genes involved in serotonin and dopaminergic pathways. Indeed, the role of serotonin in impulsivity is well recognized and dopamine system is the neuronal substrate mediating behavioural inhibition. However, the concept of impulsivity covers a wide range of "actions that are poorly conceived, prematurely expressed, unduly risky, or inappropriate to the situation and that often result in undesirable outcomes" and may be thus made up of several independent factors. Though varieties of impulsivity, inconsistency in definition and measure, in different psychiatric and non-psychiatric conditions, in the present chapter we will review genes most consistently associated with impulsivity in both healthy individuals and patients affected by major psychiatric or personality disorders.