Diagnosis is sometimes a group effort
Although hoarding has yet to be designated as a specific disorder, psychologists do have guidelines in place for making a diagnosis. Clearly, a comprehensive psychological evaluation is necessary, during which the clinician will glean as much information as possible about the patient's hoarding tendencies and emotional attachment to the objects.
He'll also need to assess the living quarters to differentiate between plain old clutter and true hoarding. Often, he'll also ask to interview family and friends who can provide him with a different view of the situation, such as whether or not the behavior is negatively impacting the patient's day-to-day life.
According to the Mayo Clinic, there are three primary characteristics that designate a hoarder. First, a true hoarder acquires excessive amounts of items that non-hoarders would perceive as useless and is emotionally unable to get rid of them. Second, the hoarder's home must be classified as practically unusable as a result of the behavior. Third, a hoarder will experience substantial distress due to the illness, both in terms of emotional stress and the impact of hoarding on his everyday life.