A missing young athlete left an emotional message on a social networking site shortly before he disappeared.
The family of Olympic hopeful Ross Clarke, 21, have become increasingly worried since he left his Essex home a week ago.
The rising 1,500m track star posted a note on Facebook in the early hours of Wednesday December 2.
It read: "Don't ever take anybody for granted, because you never know when you might lose them, and you may never get a chance to say how you really feel."
His mother, Jeanette Clarke, of Rainham, Essex, said Mr Clarke had been depressed before he went missing.
She said: "Ross has been missing for almost seven days now following some personal problems and we are very worried and concerned.
"If anyone has seen, heard or spoken to Ross, even on Facebook or the internet, please can you let the police know.
"We just want to appeal directly to Ross to come forward and contact us to let us know that you are OK. We miss you and love you very much."
Mr Clarke was last seen at 1.30pm last Friday and may have travelled to Southampton in the evening.
But police have not been able to find any evidence of him in the city and he has not used his mobile phone or Oyster travel card.
The Basildon Amateur Athletic Club member was pushing for a place in the British Olympic team as a 1,500m runner.
The runner, one of the top six 1,500m runners in Britain, has already received honours at national level in several junior age groups.
He is one of a small elite group being coached by Eamonn Martin, the last British man to win the London Marathon.
Keith Bottjer, of Basildon Amateur Athletic Club, said Mr Clarke is a "promising young talent" and an "extremely nice lad".
Mr Clarke is described as white, about 6ft 1in and of slim build, with blue-green eyes. Anyone with information should call Romford CID on 0300 123 1212.