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.

Just over one billion contactless transactions were completed in 2015, the UK Cards Association said.
More was spent using this technology last year than during the previous seven years combined.
About half of all debit and credit cards are fitted with contactless capability.
This allows shoppers to spend up to £30 on their card by placing it next to a sensor in a shop, without the need to enter a four-digit Pin.
One in 13 purchases was on contactless during the whole year, but use grew to one in eight by December, the UK Cards Association said.
One of the most common ways to use the technology is on the London Underground network, where more than a million journeys a day are paid for by placing credit and debit cards next to sensors when entering and exiting stations.
Transport for London said it was the first integrated transport authority to introduce contactless ticketing.
Concerns have been raised in the past over security of contactless cards, although the industry said that fraud levels on contactless payments were low.
Consumer group Which? said in July that, although the risks were low, it would be possible for somebody standing very close to "lift" card details without the owner knowing. Wrapping the card in tin foil, or putting it in a foil-lined wallet would guard against this.
Every contactless card has an in-built security check which requires a Pin to be entered after a number of consecutive contactless payments, to verify the genuine cardholder.

The Giants' Blair Riley replied to David Clarke's early goal as the sides went in level after the first period.
Matt Towe, James Desmarais and Steve Saviano on the powerplay were on target in the second period, with Matt Carter scoring for the hosts.
Stevie Lee pulled one back on the powerplay in the final period.
Saviano had scored four goals as the Giants saw off Fife Flyers 7-2 at the SSE Arena on Saturday night.
Jerome Leduc found the net twice in that game, with Mike Forney also getting his name on the scoresheet.
The Giants are next in action against Manchester in Belfast on Saturday 4 March.
North Wales Police has been criticised at an inquest for sending an officer to speak to a hospital patient with paranoid schizophrenia.
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One in eight purchases made on UK cards in December used contactless technology, marking a surge in the use of the alternative to loose change.
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The Belfast Giants secured their second Elite League win of the weekend by beating Nottingham Panthers 4-3 away from home on Sunday.