Bibliomania can be a symptom of obsessive–compulsive disorder which involves the collecting or even hoarding of books to the point where social relations or health are damaged.

Bibliomania is not to be confused with bibliophilia, which is the usual love of books and is not considered a clinical psychological disorder.

Other abnormal behaviours involving books include book-eating (bibliophagy), compulsive book-stealing (bibliokleptomania), and book-burying (bibliotaphy).

Compulsive hoarding in its worst forms can cause fires, unsanitary conditions (such as rat and roach infestations), and other health and safety hazards.

Listed below are possible symptoms hoarders may experience:

- They hold onto a large number of items that most people would consider useless or worthless, such as:

- Junk mail, old catalogs, magazines, and newspapers

- Worn out cooking equipment

- Things that might be useful for making crafts

- Clothes that might be worn one day

- Broken things or trash

- "Freebies" or other promotional products

- Their home is cluttered to the point where many parts are inaccessible and can no longer be used for intended purposes. For example:

- Beds that cannot be slept in

- Kitchens that cannot be used for food preparation

- Tables, chairs, or sofas that cannot be used for dining or sitting

- Unsanitary bathrooms

- Tubs, showers, and sinks filled with items and can no longer be used for washing or bathing.

- Their clutter and mess is at a point where it can cause illness, distress, and impairment. As a result, they:

- Do not allow visitors in, such as family and friends, or repair and maintenance professionals, because the clutter embarrasses them

- Are reluctant or unable to return borrowed items

- Keep the shades drawn so that no one can look inside

- Get into a lot of arguments with family members regarding the clutter

- Are at risk of fire, falling, infestation, or eviction

- Often feel depressed or anxious due to the clutter

For many years, hoarding has been listed as a symptom or a subtype of obsessive-compulsive disorder (OCD) and obsessive–compulsive personality disorder (OCPD). Obsessive-compulsive disorder is a type of anxiety disorder. People with OCD experience unwanted thoughts that incline them to do something repetitively. Some of these behaviors are excessive cleanliness and excessive toothbrushing. The current DSM says that an OCD diagnosis should be considered when:

- The hoarding is driven by fear of contamination or superstitious thoughts

- The hoarding behavior is unwanted or highly distressing

- The individual shows no interest in the hoarded items

- Excessive acquisition is only present if there is a specific obsession with a certain item

Compulsive hoarding does not seem to involve the same neurological mechanisms as more familiar forms of obsessive–compulsive disorder and does not respond to the same drugs, which target serotonin. In compulsive hoarding, the symptoms are presented in the normal stream of consciousness, and are not perceived as repetitive or distressing like in OCD patients. Despite statistics indicating that there is a prevalence of hoarding in 18% to 40% of patients with OCD, only 5% of compulsive hoarders experience symptoms of OCD. In another study, a sample of 217 patients diagnosed with significant hoarding, only 18% were diagnosed with OCD, as opposed to the 36% that were diagnosed with a major depressive disorder. There are significant differences and issues between the diagnostic features of compulsive hoarding and OCD which are being considered in a possible addition to the DSM-V of a new independent disorder such as compulsive hoarding. It is also said that there may be an overlap with a condition known as impulse control disorder (ICD), particularly when compulsive hoarding is linked to compulsive buying or acquisition behavior.

Recent findings suggest that there may be three types of hoarding: pure hoarding, hoarding plus OCD (i.e., co-morbid OCD), and OCD-based hoarding Given the aforementioned distinction, it was proposed to increase coverage of compulsive hoarding in the forthcoming Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-V), both by creating a distinct category for compulsive hoarding, provisionally named, Hoarding Disorder (either in the main manual under "obsessive-compulsive spectrum disorders" or in the appendix), and by including hoarding as a potential symptom of OCD.