Disorders of negative affect include mental health difficulties characterized by depressive mood and/or anxious distress. These diagnoses collectively constitute one of the most prevalent and impairing classes of mental health diagnoses affecting individuals across the life span. The optimal system for classifying disorders of negative affect and their underlying mechanisms remains the subject of continued debate. We first review the DSM model of classifying disorders of negative affect, before turning our attention to dimensional models and emerging theories on common factors across these disorders. We conclude with a review of supported interventions for effectively treating disorders of negative affect.