A 19-year-old man presents to the PMHNP for a psychiatric evaluation with a chief complaint of intrusive thoughts and compulsive behaviors. Of the following, which is considered the gold standard assessment tool for obsessive-compulsive disorder (OCD) severity?

Choice A reason: The OCI is a self-report questionnaire and useful for screening, but it is not considered the gold standard for severity assessment. Choice B reason: The FOCI is a brief assessment tool, helpful in research or clinical settings, but lacks the comprehensive evaluation of Y-BOCS. Choice C reason: The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) is the gold standard clinician-administered measure for assessing OCD symptom severity and monitoring treatment response. Choice D reason: The NIMH Global OCD scale is less commonly used and lacks the specificity and validation of Y-BOCS for clinical severity assessment.