There are several things that we look for. First, it is important to know what the person was like before they began drinking or using whatever substance they are using. Understanding their background helps us begin to piece the puzzle together. If so, we can ask if they remember having similar symptoms during those times. For many, depressive symptoms that persist for several weeks or more indicate the existence of a primary depression that will require treatment in and of itself.
Family history is also very important.
If there is a family history of depression, for example, it is likely that first-degree relatives are going to have depressive symptoms. Similarly, there is some difference in gender. Research suggests that for some problems like depression the coexistence of alcoholism is more evident for women than for men. These kinds of indicators are not always foolproof, but they provide a number of clues we can look for. Another similar study put the figure at 40 percent.