I think it is an impressive effect, though I agree people not wanting to be in prison is more important.
Using a panel of all defendants over the seven years after sentencing, we fnd that incarcerated defendants have a more than 60% lower mortality rate during the time of incarceration than similar defendants who were not incarcerated (an average of 230 deaths per hundred thousand annually as compared to 587 deaths per hundred thousand annually). The main sources of these differences are dramatically lower risks of mortality from homicide, overdose, or suicide during the period of incarceration. Defendants also have a lower risk of mortality from natural causes of death such as heart disease while incarcerated, potentially due to increased access to medical care
I think it is an impressive effect, though I agree people not wanting to be in prison is more important.