It follows an inquest in June into the death of David Knight, who took his own life when on home leave in St Austell while being treated in Somerset.
Dr Emma Carlyon has warned of future deaths unless the sending of vulnerable patients miles from home ends.
NHS England said it was considering the report's recommendations.
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The inquest jury said Mr Knight's suicide was contributed to by inadequate risk assessment and support while he was on leave from a private mental health unit in Weston Super Mare, Cygnet Hospital Kewstoke.
He died in May 2015 of multiple injuries after being hit by a train on a viaduct near St Austell.
Mr Knight was being treated for paranoid schizophrenia at Cygnet Hospital because there were no acute psychiatric inpatient beds available in Cornwall.
The jury also found his significant cannabis use and repeated failure to engage with Cornwall's mental health services since 2007 contributed to his death.
Ms Carlyon has called on Mr Hunt in her report to "review the provision of mental health beds in Cornwall and the Isles of Scilly to avoid the continual routine requirement for 'out of county' placements".
She added: "I considered that you should be a aware of the matter raised at inquest with a view to preventing future deaths."
An NHS England spokesperson said: "Our heart goes out to the family at this difficult time.
"Our expectation is that all local health systems will end the practice of sending patients far away from home for treatment by 2021 at the latest, and expect to see significant progress on this over the coming year."
A coroner has written to Health Secretary Jeremy Hunt calling for a review of acute mental health beds in Cornwall.