Iwan Wyn Lewis of Penygroes, Gwynedd, had been sectioned at Ysbyty Gwynedd after allegedly assaulting his mother.
The 36-year-old was visited by an officer in April 2016 about his bail arrangements, which a doctor said could have added to his distress.
His body was found in the Menai Strait on 2 May.
Mr Lewis was receiving treatment at the hospital's Hergest unit and was later moved to the Cynan ward where he received the visit from the officer.
Speaking at the inquest in Caernarfon on Thursday, consultant psychiatrist Dr Olufemi Adebajo said he was "extremely unhappy" about the visit.
"I don't think the police should be able to come to the ward without special permission," he said.
Asked by coroner Nicola Jones whether the conversation with the officer could have added to Mr Lewis' agitation and distress, Dr Adebajo said: "It's quite possible - even likely".
He said he had known Mr Lewis for more than two years and never considered him to be a suicide risk.
The day before his death, he had asked staff for extra medication because he said he was feeling agitated, but they did not change his dosage because they could see no sign of agitation.
On the evening of 2 May, Mr Lewis told staff he was going to the shop, but 45 minutes later his body was found in the Menai Strait.
The inquest continues.
North Wales Police has been criticised at an inquest for sending an officer to speak to a hospital patient with paranoid schizophrenia.