Glass Prison can refer to a few things. Generally it is used to describe an addiciton to alcohol. However, it can also be used in the context of emotional problems. By having a mental problem that nobody can see, one feels essentially trapped in an invisible box. A 'glass prison' of such.
"I cannot break out of my glass prison all alone"
by Roddn Smith November 20, 2006
An addiction to alcohol.
I'm trapped in my glass prison, can't break out all alone.
by Taylor February 17, 2005