Deduction

Yes, the expenses in a rehab center are an itemized medical expense deduction. You can only deduct an amount of total medical expenses greater than 7.5 percent of your AGI. 

You can enter the cost as Medical Expenses. 

You would only get the deduction for the expense if your itemized deductions are more than the Standard Deduction. For most people, the standard deduction is more. 

Link explaining the Standard Deduction and Itemized Deductions