Many of us have trouble parting with our possessions—even when we no longer need them. Some people hold onto decades’ worth of receipts, newspapers, and other seemingly useless items. They have hoarding disorder—a mental health condition characterized by a compulsive need to acquire and keep possessions, even when they’re not needed. Exactly when a “pack rat” crosses the line into true hoarding has to do with the intensity with which they’re saving, and the difficulty getting rid of things. Severe hoarders can accumulate so much that they render their living spaces unusable—and dangerous. Hoarding also takes an emotional toll on families and friends. Experts recommend treating hoarders with hoarding cognitive behavioral therapy (CBT) to help the person better understand why he or she is hoarding, and to improve decision-making, organizational, and problem-solving skills.