Jonathan Rhys Meyers was hospitalised after a suspected suicide attempt on Tuesday.
The 'Tudors' star - who has been in rehab five times for alcohol problems - refused treatment by paramedics for more than 30 minutes, meaning they were forced to call police and he was eventually taken away by ambulance to a facility near his home in Maida Vale, north London.
A source said: "This is very sad. It was the opinion of those present that he tried to take his life."
Worried neighbours saw the 33-year-old actor - who was believed to have overdosed on unspecified pills - rushed to hospital.
One onlooker told The Sun newspaper: "I saw the ambulance arriving and was worried to death.
"Jonathan is a lovely guy. You see him all the time in the street. He says hello and is very pleasant. I hope he is fine."
The 'Velvet Goldmine' actor was discharged from hospital yesterday but would only answer "no comment" when questioned on whether he had tried to commit suicide.
A police spokesperson confirmed they had been asked to attend the incident.
An official said: "Officers were called by London Ambulance Service following reports of a man refusing treatment. The man was taken to hospital."