Neurobiological bases for impulsive and compulsive behaviour: Implications for pharmacological and psychological interventions

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Pathological impulsivity and/or compulsivity charcterize a wide range of mental disorders, including impulse control disorders, obsessive-compulsive and related disorders, personality disorders, substance use disorder and behavioural addictions. Impulsivity is a complex, multidimensional personality trait which consists of at least two dimensions: disinhibition (impulsive actions) and impulsive decision-making or impulsive choice, with an underestimation of potentially dangerous consequences (e.g., aggression, pathological gambling, hypersexuality). Compulsivity refers to repetitive, ritualized behaviours that are performed according to a certain rule and in a certain manner, most often in order to reduce anxiety or discomfort. Impulsivity and compulsivity share an inability to stop or delay repetitive behaviour. Over time, impulsive behaviour can become compulsive (when it loses the excitement characteristic), and compulsive behaviour can become impulsive (enhanced by habituation). Many psychiatric disorders include elements of both compulsivity and impulsivity, showing a different predominance during the various stages of the disorder (e.g. in substance use disorder impulsivity usually dominates in the early stages of the disorder, and compulsivity in the later stages). The neurobiological basis for impulsivity and compulsivity may include excitatory neurotransmitters such as dopamine, norepinephrine and glutamate, or inhibitory neurotransmitters such as serotonin and gama-aminobuteryc acid, as well as dysfunction in the prefrontal cortex and limbic system. Increased activity of the frontal lobes can lead to compulsive disorders, and reduced activity can lead to impulse control disorders. Results of neurobiological studies suggest that there is a hereditary and/or environmentally conditioned predisposition to lower receptor availability of dopamine in the midbrain, a neurotransmitter whose imbalance is involved in behavioural disinhibition and pathological hypersensitivity to time delayed rewards, i.e. discarding the time delay for immediate reward, which is the basis for impulsive behaviour. On the other hand, compulsive behaviour is primarily associated with serotonin dysfunction, but this disregulation may indirectly affect the functioning of the dopaminergic and other neurotransmission systems. This paper presents an overview of clinical and neurobiological similarities and differences in impulsivity and compulsivity through a wide range of mental disorders, with implications for pharmacological and psychological interventions.