Insomnia, characterized by an inability to initiate and maintain sleep, is a defining feature of mood disorders such as depression. CBT has been found to be an effective treatment for depression-related insomnia. This study will determine the effectiveness of CBT in treating insomnia that is secondary to depression. In addition, this study will assess the relationship between insomnia and depression, since previous studies have shown that insomnia may not only be a symptom of depression but may also indicate the onset of a depressive episode.