Summer camp,

A codeword for a long-term psych ward or residential behavioral health facility. Typically used when in public or when speaking with people who don't know you were in a mental facility.

"Oh, sorry for replying so late, I was at a 'summer camp,'"

Summer Camp Syndrome

That feeling of sadness or loneliness you get when you come home from a summer camp or a retreat and go back to normal life.

Ever since the trip I’ve felt lonely and bored I must have Summer Camp Syndrome.