Caloric Vestibular Stimulation for Modulation of Insight in Obsessive-Compulsive Spectrum Disorders

This study investigates whether caloric vestibular stimulation can modulate a measure of insight in obsessive-compulsive spectrum disorders.

Obsessive-compulsive and related disorders (OCRD), including obsessive compulsive disorder and body dysmorphic disorder, are chronic and disabling conditions characterized by recurrent intrusive thoughts and associated compulsive behaviors that affect millions of individuals in the US each year. Individuals affected by OCRD differ in insight, or the degree to which they understand their intrusive thoughts to reflect illness. Impairments in insight limit individuals' motivation to engage in care and predict worse outcome in those who access treatment. This study seeks to explore whether unilateral stimulation of the vestibular system, which activates cortical areas hypothesized to underlie clinical insight, may beneficially modulate insight in individuals with OCRD.

OCRD participants in this arm will receive an approx 60 second infusion of distilled cold(4)c water in their right external ear canal, with before and after measures of OCRD symptom severity and insight.

OCRD participants in this arm will receive an approx 60 second infusion of distilled cold(4)c water in their left external ear canal, with before and after measures of OCRD symptom severity and insight.

Cold water creates a convection current in the semicircular canal of the vestibular apparatus, leading to brief (<3 min) and typically well tolerated sense of rotational movement. Similar stimulation is routinely used in standard vestibular diagnostic testing.

Changes in clinical insight will be rated using the BABS, a gold-standard measure for assessing multiple dimensions of clinical insight across psychiatric disorders. The BABS is a 24 point scale for which scores ≥13 suggest poor or absent insight.

Inclusion Criteria: Age 18-65 Primary diagnosis of Obsessive-Compulsive Disorder, Body Dysmorphic Disorder, Illness Anxiety Disorder or Somatic Symptom Disorder (excluding "with predominant pain") Strongly held OCRD-related concerns meeting BABS score criterion. No recent change in psychopharmacological treatment, if any Capacity to provide informed consent Exclusion Criteria: Psychiatric or medical conditions (eg, vertigo, history of otological surgery) that might make participation unsafe Pregnant or nursing women Active or recent substance use