Mental illness is a big driver of Medicaid costs because it is twice as prevalent among beneficiaries of the public insurance program for the poor as it is among the general population. Studies show that enrollees with mental illness, who also have chronic physical conditions, account for a large share of Medicaid spending.Yet many Medicaid programs, including Florida’s, have traditionally contracted with separate companies to provide coverage for mental health services, making coordination more difficult. “We don’t want to have a situation where your brain is in one HMO, your teeth are in a second HMO and your eyes are in a third HMO,” said Florida Medicaid Director Justin Senior. “Your whole head should be in the same organization and that is why we have done this reorganization.”About 140,000 low-income Floridians are expected to be eligible and Magellan predicts about 20,000 will participate voluntarily in the first year. Medicaid recipients who meet the plan’s criteria will automatically be assigned to it by the state, though they have the option to switch to a different managed care plan within 90 days of enrollment.Coverage begins July 1 in Miami-Dade and Broward counties, then will roll out to other regions by September.