I think that's right. One of my summer jobs involved doing research for a "think tank". Because the think tank did work for the federal government including the Defense Department, I had to go through a security check to get into the building and work there. This involved a background check and filling out every form ever created.
It also involved pulling out some of my hair for a drug test. The person who took the hair sample told me that they were looking to see if I had used anything over the past few months. They weren't concerned about the last week or the night before because they figured I knew I'd be drug tested and would have stopped using. But they told me if I had used anything over the past few months they would find it.