Clinical and Biological Correlates of Obsessive-Compulsive Disorder and Online Mindfulness-Based Cognitive Therapy

Patients with OCD.

Inclusion Criteria:

* Diagnosis of obsessive-compulsive disorder (OCD) according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)
* Age between 18 and 45 years
* Stable pharmacological treatment for at least 3 months prior to the start of the experimental intervention
* No previous experience with mindfulness meditation, or previous mindfulness meditation experience with no practice during the 12 months prior to study enrollment
* Ability and willingness to provide written informed consent.

Exclusion Criteria:

* Diagnosis of schizophrenia spectrum or other psychotic disorders, including schizoaffective disorder
* Diagnosis of bipolar and related disorders
* Major depressive disorder in an acute phase
* Active substance use disorder or alcohol use disorder as the primary diagnosis
* Personality disorders of clinically significant severity
* Documented major neurocognitive disorder. Neurological conditions or medical conditions with a clinically significant impact on cognitive or mental functioning
* Previous mindfulness meditation practice within the 12 months prior to study enrollment
* Inability or unwillingness to provide informed consent

Healthy subjects.

Inclusion Criteria:

* Age between 18 and 45 years, with age matching within a maximum difference of ±3 years from the corresponding index patient. In all cases, control participants must be at least 18 years and no older than 48 years
* Voluntary participation in the study.
* Ability and willingness to provide written informed consent

Exclusion criteria:

* Age younger than 18 years
* History of psychiatric disorders, as assessed using the Structured Clinical Interview for DSM-5 Disorders - Clinician Version (SCID-CV)
* Intellectual developmental disorder.
* Current substance use disorder or alcohol use disorder
* Neurological disorders, including Parkinson's disease, major neurocognitive disorders, neurodegenerative syndromes, ataxias, multiple sclerosis, cerebrovascular events (stroke or transient ischemic attack \[TIA\]), central nervous system neoplasms, epilepsy, history of seizures, or clinically significant tremor
* Systemic medical conditions (e.g., diabetes mellitus, atherosclerosis, chronic arterial hypertension, or malignancies) requiring pharmacological treatment
* Current or previous mindfulness meditation practice within the 12 months prior to study enrollment