Compulsive hoarding is the acquisition of items that the hoarder has difficulty discarding. The hoarder is preoccupied with acquisition, has minimal insight into the purpose behind his behaviour and undertakes the hoarding in isolation.

Hoarders find themselves acquiring items and while considered valuable to them, others see the acquisitions as of no value and are bewildered as to why the acquisitions occur.

Hoarders lose the ability to differentiate between collecting for sentimentality, monetary or intrinsic reasons and acquire a greater number of items upon which they place significant value.

Difficulty in organising the acquisitions is the norm. Efforts to reorganise the acquisitions are resisted and touching of the objects is viewed as threatening. Compulsive hoarders deny they have a problem, resist intervention and become aggressive if intervention occurs, factors that have lead to uncertainty as to the prevalence of compulsive hoarding.

Evidence is suggestive, however, that compulsive hoarding may indeed be common. Moreover, it has been identified in several psychiatric and non-psychiatric illnesses. Hoarding in these illnesses may be either a specific or a non-specific symptom. Studies of adults whose primary diagnosis is OCD show that 30% have obsessions and 18% compulsions concerned with hoarding.

Compulsive hoarding is more common in females in all age groups. Childhood onset is the norm with one study showing that 66% began hoarding in childhood, 25% in their twenties and 9% after the age of 24.

Compulsive hoarding in the elderly may have a different aetiology to earlier onset in that it may reflect pre-existing personality characteristics, symbolise relationships with loved ones who have died or be used to express denial of aging; the collection counters the process of depletion of the body: “objects do not decay but the body does”.

The Greek philosopher Diogenes in the 4th century BC recognised a phenomenon in the elderly associated with hoarding that he named after himself. Those with Diogenes Syndrome live in filthy conditions, show a lack of concern with their predicament, deny luxury, hoard excessively and often hoard rubbish (syllogomania). .