Britney Spears has checked in to rehab to treat her substance abuse issues, Wonderwall.com can reveal. The Toxic singer, 44, "voluntarily" enrolled into the facility, her reps said, amid pressure from her inner circle. 'She's hit rock bottom' Britney Spears insiders say the situation 'served as a wake-up call.' By: MEGA The star's latest spell in rehab comes weeks after her DUI arrest in California, during which the troubled singer appeared to be "driving under the influence of a combination of drugs and alcohol," authorities said.