The Health Belief Model. Other theories and models are also at this site. This site doesn't have the credibility of a primary source, but it's a good starting reference.
Helping Ex-Inmates Stay Out Of by The ER Brings Multiple Benefits by Rae Ellen Bichell for NPR Morning Edition (Dec. 5, 2016). Studies show that newly released prisoners (within two weeks) have a higher risk of dying. "Wang says the primary causes of death after incarceration include overdose, heart disease, suicide and cancer — often treatable things, if you catch them early enough." There are several reasons - needing to learn how to use the system, discrimination, etc.