Police forces in England and Wales received one call every 90 seconds last year about a missing person, official figures show.
Data from the National Crime Agency (NCA) reveal more than 335,000 missing person calls were made in 2015/16.
The figure is an increase of 15% on the previous year.
The data also show that around one in every five missing persons was an individual who had some form of mental health issue.
The families of those searching for a loved one have said the experience leaves them devastated.
Margaret Cooper, who has been searching for her son Steven, who went missing from his home in Huddersfield in 2008, said: "It's the not knowing, that's the worst thing.
"One day I think he's dead and then another I think he's still alive."
Steven was last seen in Scotland and officers from West Yorkshire searched Loch Laggan in 2011 as part of their investigation, but no sign of him has ever been found.
Ms Cooper added: "If I had a body, because he'd died, I could then grieve - but having no idea what's happened to him has left me in limbo.
"Throughout the initial search it just didn't feel real, it was like being in a bubble, and it was so hard because there was no reason we could think of as to why he would disappear."
The NCA said its latest report was its "most complete assessment to date" of people going missing in the UK.
The majority of police forces reported a rise in the number of missing people calls they had handled, although the NCA warned year-on-year comparisons should be treated with caution as each force records data differently.
Det Ch Insp Chris Gibson of West Yorkshire Police, which said it had seen a 72% increase in the number of calls received, said: "I think people are more aware now of the issue of missing people.
"We've also improved the way we record missing people, so that contributes to the rising numbers.
"But, for us, this is a really important issue and when we identify that a vulnerable person is missing we'll have officers on the ground out searching in less than 15 minutes".
For the first time the NCA has also published data that examines why people go missing.
It shows that one in five people who disappear are reported to have some form of mental health issue.
Abduction and relationship issues are also two of the most common reasons why people disappear.
Claire Cook, from the charity Missing People, said the issue affects people from all backgrounds.
She said: "If someone goes missing it signals there's a problem.
"For adults, the common issues are mental health problems and relationship breakdowns, whilst if a child goes missing it's often a sign that there's something wrong at home.
"What's clear is that it's not just the police that have to deal with missing people, this is a societal issue and one we have to tackle together".