What Causes Depression And Panic Attacks While On Ambien?

My boyfriend has been on Ambien for about a year and a half now. He had gone thru the loss of a job after 5 years, the death of his mother and an auto accident all about that same time. Now he cannot sleep, even with the Ambien and is experiencing panic attacks and syptoms of depression. I am wondering if these could be related to the long term use of the Ambien, or just sleep deprivation or both.