Vulnerable prisoners must be identified more effectively, an investigation into a death at Magilligan has found.
Paul Johnston was 27 years old when he was found dead in his cell on August 4, 2017.
A probe by the Prisoner Ombudsman found he did not intend to take his own life and his death was drug-related.
Dr Lesley Carroll said she was concerned about the "devastating impact of substance misuse and poor mental health" that led to the tragedy.
While some aspects of Mr Johnston's care "could have been better", Dr Carroll said she could not say with certainty it would have changed the outcome.
"I offer my sincere condolences to Paul's mother and father, his family and wider circle of friends," she said.
"The death of a loved one is always difficult. The fact that a death occurs in prison custody has particular difficulties given the loss experienced by the family and also the wider prison community."
She continued: "I am concerned about the devastating impact of substance misuse and poor mental health which resulted in Paul's untimely death. Sadly, we know this is not an issue confined to those who live and work within prisons.
"This problem requires a broad response taking the whole life of communities into account and targeted at both prevention, by addressing the root causes of behaviours that can result in people losing their lives in these circumstances, and also response so that people can access effective services when they most need them.
"Prisons should play their part in an overarching strategy but the challenge is systemic and society-wide."
Her report contains seven recommendations for the Prison Service and the South Eastern Trust, with the hope it will prevent further deaths.
Managing vulnerable prisoners was the key issue, with the Prison Service and Trust advised to review the assessment of risk management of those presenting with complex case histories.
The Governor of Magilligan Prison was also asked to review the Vulnerable Persons' Policy to make sure it was fit for purpose.
An approach for inter-prison transfers should be agreed, she said, between the Prison Service and Trust so any clinical risks can be properly managed.
The withdrawal of alcohol, and if a prisoner is not taking their medication, should be monitored. Prisoners who stop taking their medication should be offered a GP appointment to discuss this, with any unused medication disposed of.
On record keeping, the Trust was advised to audit health care records to comply with national and local standards.
Tackling the supply of drugs in prison was also flagged, with the Prison Service encouraged to explore new technology and equipment to better detect drugs concealed in a person.