The Research Domain Criteria (RDoC) approach seeks to address the neurobiological mechanisms of sensory symptoms in patients with obsessive-compulsive disorder (OCD) by investigating dimensional components of behavior that more closely align with brain circuitry. This project focuses on the dimensional symptom of sensory phenomena (SP), which are uncomfortable or aversive sensory experiences that drive repetitive behaviors in OCD, including "not just right" sensations, physical urges, and sensations of disgust. SP are very prevalent, occurring in 60-80% of OCD patients, and experienced as highly distressing. Unfortunately, SP are not well addressed by standard treatment approaches, which may be in part because their neurobiological mechanisms are not well understood.

This project builds on our preliminary data to (1) investigate the neural mechanisms of SP in large OCD cohort showing the full range of SP severity and (2) probe for familial risk markers in unaffected siblings of patients. For Aim 1, SP will be measured in 100 OCD patients using the Sensory Phenomena Scale. Diffusion and fMRI data will be acquired during rest and fMRI tasks. In order to identify familial risk markers, Aim 2 will compare sensory phenomena and neural circuitry between OCD probands, 50 unaffected biological siblings of OCD patients, and 50 unrelated healthy controls without a family history of Axis 1 disorders.

This project investigates the neurobiological mechanisms of sensory symptoms in patients with obsessive-compulsive disorder (OCD) and their siblings using task-based fMRI, resting-state functional connectivity, and diffusion MRI approaches. OCD is a chronic disorder presenting a high public health burden. Treatment presents a particular challenge because OCD is extremely heterogeneous, with clusters of symptoms likely derived from differing neural etiologies.

Inclusion Criteria:

• Fluent (speaking and writing) in English

Additional criteria for healthy controls (HC):

• Lifetime absence of major Axis I diagnosis according to Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 criteria
• Not taking psychotropic medications
• No first-degree biological relatives with OCD

Additional criteria for siblings (SIB):

• First-degree biological sibling of a person with OCD

Additional criteria for OCD patients:

• Diagnosis of OCD according to DSM-5 criteria.

Exclusion Criteria:

• Current moderate or high suicidality as assessed through the Mini International Neuropsychiatric Interview (MINI) 7.0.2 suicidality module
• MRI contraindications such as claustrophobia, ferrous implants, braces, or pacemakers
• Major neurological illness (e.g., self-reported history of organic mental syndromes, head trauma, migraines, seizures, other Central Nervous System (CNS) disease, or other significant medical illness that would make participation unsafe or unfeasible)
• Positive urine toxicology or pregnancy test
• Any disability or health problem that prevents them from completing study procedures (e.g. back problems, severe carpal tunnel syndrome, impaired vision that is not corrected with glasses or contact lenses, etc.).
• Present diagnosis of alcohol use disorder or substance use disorder (moderate or severe)
• Present or previous diagnosis of psychosis, bipolar disorder, or major developmental disorder (autism spectrum disorder, intellectual developmental disorder) based on DSM-5 criteria.

This study will involve 18-60 year-old male or female volunteer subjects of any racial or ethnic group. This will include 100 OCD patients, 50 unaffected biological siblings (SIB) and 50 healthy controls (HC).