It's a sad state of affairs that we have off-loaded mental health issues to our prisons. Numbers vary from study to study, but in male prisons they've studied they find anywhere from 40% to 60%+ of male prisoners have some sort of mental health diagnosis--some studies put it as high as 70% of all male prisoners if you include undiagnosed.
Female prisoners it's even higher. 90 percent of female prisoners in a Wisconsin state women's prison had an active mental health diagnosis.
Within those populations, a third to one-half will have psychiatric conditions serious enough to require regular treatment beyond prescribing medication.
And the cost of incarcerating mentally ill individuals is crazy. e.g., In Michigan it costs $95,000 a year to house, feed, provide medication, support staff, etc for each prisoner with a mental health diagnosis--compared to $35,000 for prisoners without mental health problems. For the mentally ill who are not incarcerated, Michigan spends only $6,000 each per year, on average.