The Shruti tree is named after the character Shruti Acharya, a student doctor who took her life in the series, which drew millions of viewers on BBC One in February.
Mr Kay joined NHS leaders, charities and bereaved families to plant the first official memorial, after an estimated 300 nurses died by suicide in the seven years to 2017.
A plaque next to the tree said: “In memory of healthcare professionals who have died by suicide. Take care of those who take care of others.”
More than 220 nurses attempted to end their lives during the first year of Covid in 2020, according to the Laura Hyde Foundation, which saw a 550 per cent rise in demand for clinical mental health support from medical staff in 2020,
The charity, set up in memory of Navy nurse Laura Hyde, said that two healthcare workers die by suicide every week on average, while a doctor takes their own life once every three weeks.
I’m sad to say we’ve failed a lot of these medical professionals
Mr Kay told the PA news agency at the ceremony: “Suicide simply is not spoken about and in my experience, sadly, sometimes even the staff don’t know, it’s simply brushed under the carpet. We need to talk about this openly and honestly.”
In a speech to a crowd gathered in front of the sapling, the comedy writer added: “I’m sad to say we’ve failed a lot of these medical professionals and I hope this is a turning point.”
Exterior shots for This Is Going To Hurt were filmed at Ealing Hospital, where Mr Kay previously worked until he wrote his diaries, and many fans have visited the site hoping to find a memorial tree, which was planted for Shruti in the show.
But it did not exist, sparking months of conversations between Mr Kay and the London North West University Healthcare NHS Trust to bring it to fruition.
Prof Sir Stephen Powis, the national medical director of NHS England, said the memorial marked a “pledge for all of us” to prioritise mental health and “remember to be kind”.
“This now needs to be something that we focus on permanently within the NHS. We have momentum and we need to keep that momentum,” he said before picking up a spade to help plant the tree.
“It’s been an extraordinary effort (during the pandemic) but it’s absolutely taken its toll on people’s mental health, on wellbeing, people are exhausted and just looking for a break … everybody is longing in some way to get back to that normal, albeit it will be a new normal.”
Actress Ambika Mod, who starred as Shruti in the TV series, told PA it was “incredibly heart-warming and special” and the series had “blown all expectations out of the water”.
“I was so surprised to hear that people had been looking for the tree that was planted in the show, and I’m really glad there is now a place where they can come to pay their respects.”
Nearly as many patients presented to NHS Practitioner Health, a wellbeing service for doctors and dentists in England, between April 2020 and March 2021 as in the first 10 years of the service, the charity Doctors in Distress said.
Jennie Barnes, a mental health nurse from the Laura Hyde Foundation whose medical worker niece, Ms Hyde, took her life, said too many medics “see suicide as a way out”.
“We’re facing a new pandemic now of health staff with mental health problems,” she said, urging NHS leaders to add mental health champions to all boards and ensure staff can access 24-hour support helplines as staff shortages mount.