Sussex Police has asked anyone who sees the teenager, named only as Melissa, to dial 999.
“We are searching for Melissa who is missing from the Crawley area,” a police statement read.
"Melissa is 16, 5ft 4in and has long brown hair. She was last seen wearing a full grey tracksuit.
“If you see her, please call 999 quoting serial 1661 of 18/09.”
1. Horsham teenager is missing
If you see Cayden, you are asked to call 999, quoting serial 1235 of 04/02 Photo: Sussex Police