Yes, you can deduct your 2018 out of pocket expenses for a rehab facility as medical expenses.
Per IRS Publication 502 Medical and
Dental Expenses, you may include the amounts you pay for inpatient treatment at a therapeutic center for the treatment of an addiction or a medical condition as medical expenses. This includes the costs of meals and lodging provided by the facility for the treatment. You must itemize deductions to claim medical expenses, and only the amount that exceeds 7.5% of your adjusted gross income is deductible.
To enter your medical expenses: https://ttlc.intuit.com/replies/4774888
