To understand pathological gambling (PG) one must understand the disorders that co-occur with PG. A 2005 study of more than 43,000 representative Americans found that people with PG often have other mental health disorders at the same time (called comorbid disorders). Examples of these include alcohol use disorders (73 percent), drug use disorders (38 percent), mood disorders (49 percent), anxiety disorders (41 percent) and personality disorders (60 percent) (N. M. Petry, Stinson, & Grant, 2005). While it is reasonable to hypothesize that genetic and environmental factors are both responsible for these co-occurrences, more research is necessary to learn how the two variables work together. One study that addresses these questions was recently published in the Journal of Affective Disorders (Giddens, Xian, Scherrer, Eisen, & Potenza, 2011). The study used data from 7,869 male twins to examine the relationship between PG and two anxiety disorders, generalized anxiety disorder (GAD) and panic disorder (PD).