Police have made a direct appeal to missing student Richard Okorogheye asking him to get in touch - saying their only concern is for his safety.
Met Police Detective Superintendent Danny Gosling said: "People can go missing from home for any of number of reasons. Our job is not to cast judgement but to work to find them and bring them home safely.
"My message to Richard is clear: Our only concern is your safety. You are not in trouble and have done nothing wrong.
"If you read or hear this message we would ask you to contact us, or someone you trust, to let us know you are safe."
The 19-year-old left his family home in the Ladbroke Grove area of west London on the evening of Monday 22 March, boarded a bus, and later took a 20-mile taxi ride from the W2 area of the capital to a residential street in Loughton, Essex.
He was last seen on CCTV in Loughton walking towards Epping Forest, in the early hours of Tuesday 23 March.
Specialist police search officers, with mounted police and a dogs unit, have been searching the forest since Wednesday - but nothing of relevance has been found yet.
The Oxford Brookes student, who has sickle cell disease, had been struggling to cope with shielding for the past year and it is believed he did not take his daily medication with him.
On Thursday, the force said Mr Okorogheye's phone had not been in use since his disappearance.
Mr Okorogheye's mother, Evidence Joel, told Sky News her son had never mentioned Loughton and she thinks he went there to "meet somebody".
"Someone was waiting for Richard," she said.
Anyone with information is asked to call police on 101 quoting 21MIS008134.