The case came to light after the young woman escaped from a closed ward at Blakstad Hospital in Akerhus on July 23rd.
When the young woman was returned to the ward the next day, she was examined by a doctor and found to have had sex the previous day.
According to an internal hospital memo obtained by VG newspaper, the man admitted both to having a relationship and helping the woman escape.
The memo from July 25th noted that the "absolutely extraordinary circumstances", which included "planning escape, strangulation attempts (...) and trans-boundary sexual behaviour", meant that the hospital would need to alert its supervisory authority and possibly also the police.
The sexual relationship between the two had continued over several months, with the man receiving a caution from the hospital in May, the memo continued.
Police superintendent Olav Brubakk said that police were waiting to receive certain papers before deciding whether to press charges against the man.