Impulse disorders: new developments in an evolving field

In the research planning agenda leading up to DSM-V, two topics are being discussed that will influence the way that we view and conceptualize impulsive and compulsive disorders. First, there is the concept of removing obsessive-compulsive disorder from the anxiety disorders and creating an obsessive-compulsive behaviors spectrum. This is a new category that includes a group of disorders sharing common features. Second, there is the concept of expanding the impulse control disorders-not otherwise specified to include four new disorders, which will be called impulsive-compulsive disorders. The obsessive-compulsive behaviors disorders would include various disorders that share clinical features (obsessive thoughts or compulsive behaviors), course of illness, comorbidity, family/genetic transmission, neurocircuitry and treatment-response profile with OCD. These disorders may fall within three groupings: 1) repetitive behaviors to reduce anxiety focused on body image or sensations (i.e., body dysmorphic disorder, hypochondriasis); 2) repetitive behaviors to regulate arousal (i.e., pathological gambling, trichotillomania, compulsive-impulsive sexual behavior, compulsive-impulsive Internet usage); and 3) neurological disorders with basal ganglia impairment (i.e., Tourette's syndrome, autism spectrum disorders). The four proposed impulsive-compulsive disorders include impulsive-compulsive buying disorder, impulsive-compulsive sexual behavior, impulsive-compulsive Internet usage and impulsive-compulsive excoriation (skin-picking). These disorders are associated with arousal and pleasure initially and then, over time, become driven behaviors to reduce dysphoria. The relationship between OCD and these obsessive-compulsive behavior spectrum disorders, as well as impulse control disorders, will ultimately be determined by demonstrating a shared underlying pathophysiology and endophenotype. This will require research utilizing neuroimaging studies to define the functional neurocircuitry (e.g., positron emission tomography, functional magnetic resonance imaging) and genetic studies integrated with studies of phenomenology, endophenotyping and treatment response, integrated with different models of classification. Dimensional approaches to compulsivity and impulsivity and factor analytic models to elicit subfactors (i.e., obsessions, higher order and lower order repetitive behaviors) or subdimensions (i.e., motor, attentional and non-planning components of impulsivity) will also need to be incorporated with these approaches. These future studies and proposed changes in the conceptualization of compulsivity and impulsivity will have important implications to the way that clinicians recognize and treat these common and disabling conditions.