It is generally acceptable to write about personal experiences with mental illness in college essays, as long as the essay is focused on a larger topic such as mental health awareness or overcoming adversity. If you are considering writing about your experience with OCD in your college essay, it is important to consult with your college guidance counselor or a college admissions officer to get specific guidance on what is acceptable for your essay. In general, it is best to avoid writing about sensitive topics such as mental illness in college essays unless you are confident that you can handle the topic with sensitivity and maturity.