The Solitary Confinement Study and Reform Act of 2018 This bill establishes the National Solitary Confinement Study and Reform Commission: (1) to study the impact of solitary confinement in correctional facilities on governments, communities, and social institutions; (2) to report findings; and (3) to recommend national standards to reduce the use of solitary confinement. The bill directs the Department of Justice (DOJ) to publish national standards to reduce solitary confinement in correctional facilities. The Bureau of Prisons must comply with the national standards immediately. A state or local government must certify compliance with the national standards to be eligible for DOJ-administered grant program funding to construct, maintain, or operate correctional facilities.