In addition to psychometric questions, we will also address clinically meaningful questions related to pain, depression, and the relationship between the two. The complex relationship between pain and depression has been observed for years. Both syndromes are mutually exacerbating—pain worsens depression and depression worsens the experience of pain. The domain-related issues of greatest interest focus on the interaction between depression and pain and its impact on treatment outcome (including changes in symptoms of both depression and pain, in acute clinical status, and in social functioning).