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.

CBD is frequently comorbid with mood, anxiety, substance abuse and eating disorders. People who score highly on compulsive buying scales tend to understand their feelings poorly and have low tolerance for unpleasant psychological states such as bad moods. Onset of CBD occurs in the late teens and early twenties and is generally chronic. CBD is similar to, but distinguished from, OCD hoarding and mania. Compulsive buying is not limited to people who spend beyond their means; it also includes people who spend an inordinate amount of time shopping or who chronically think about buying things but never purchase them. Promising treatments for CBD include medication such as selective serotonin reuptake inhibitors (SSRIs), and support groups such as Debtors Anonymous.

The terms compulsive shopping, compulsive buying, and compulsive spending are often used interchangeably, but the behaviors they represent are in fact distinct. (Nataraajan and Goff 1992) One may buy without shopping, and certainly shop without buying: of compulsive shoppers, some 30% described the act of buying itself as providing a buzz, irrespective of the goods purchased.

Trichotillomania is classified as compulsive picking of hair of the body. It can be from any place on the body that has hair. This picking results in bald spots. Most people who have mild Trichotillomania can overcome it via concentration and more self-awareness.

Those that suffer from compulsive skin picking have issues with picking, rubbing, digging, or scratching the skin. These activities are usually to get rid of unwanted blemishes or marks on the skin. These compulsions also tend to leave abrasions and irritation on the skin. This can lead to infection or other issues in healing. These acts tend to be prevalent in times of anxiety, boredom, or stress.

The main observed symptoms of OCPD are (1) preoccupation with remembering past events, (2) paying attention to minor details, (3) excessive compliance with existing social customs, rules or regulations, (4) unwarranted compulsion to note-taking, or making lists and schedules, and (5) rigidity of one's own beliefs, or (6) showing unreasonable degree of perfectionism that could eventually interfere with completing the task at hand.

OCPD's symptoms may cause varying level of distress for varying length of time (transient, acute, or chronic), and may interfere with the patient's occupational, social, and romantic life.

About 50 million people in the world today appear to suffer from some type of obsessive-compulsive disorder. Sufferers are often more secretive than other people with psychological problems, so the more serious psychological disorders are diagnosed more often. Many who exhibit compulsive behavior will claim it is not a problem and may endure the condition for years before seeking help.

Intermittent explosive disorder or IED is a clinical condition of experiencing recurrent aggressive episodes that are out of proportion of any given stressor. Earlier studies reported a prevalence rate between 1%-2% in a clinical setting, however a study done by Coccaro and colleagues in 2004 had reported about 11.1% lifetime prevalence and 3.2% one month prevalence in a sample of a moderate number of individuals (n=253). Based on the study, Coccaro and colleagues estimated the prevalence of IED in 1.4 million individuals in the US and 10 million with lifetime IED.

Some of the fundamental components of kleptomania include recurring intrusive thoughts, impotence to resist the compulsion to engage in stealing, and the release of pressure following the act. These symptoms suggest that kleptomania could be regarded as an obsessive-compulsive type of disorder.

People diagnosed with kleptomania often have other types of disorders involving mood, anxiety, eating, impulse control, and drug use. They also have great levels of stress, guilt, and remorse, and privacy issues accompanying the act of stealing. These signs are considered to either cause or intensify general comorbid disorders. The characteristics of the behaviors associated with stealing could result in other problems as well, which include social segregation and substance abuse. The many types of other disorders frequently occurring along with kleptomania usually make clinical diagnosis uncertain.

There is a difference between ordinary theft and kleptomania: "ordinary theft (whether planned or impulsive) is deliberate and is motivated by the usefulness of the object or its monetary worth," whereas with kleptomania, there "is the recurrent failure to resist impulses to steal items even though the items are not needed for personal use or for their monetary value."

OCD can present with a wide variety of symptoms. Certain groups of symptoms typically occur together. These groups are sometimes viewed as dimensions or clusters that may reflect an underlying process. The standard assessment tool for OCD, the Yale–Brown Obsessive Compulsive Scale (Y-BOCS), has 13 predefined categories of symptoms. These symptoms fit into three to five groupings. A meta analytic review of symptom structures found a four factor structure(grouping) to be most reliable. The observed groups included a "symmetry factor", a "forbidden thoughts factor", a "cleaning factor" and a "hoarding factor". The "symmetry factor" correlated highly with obsessions related to ordering, counting, symmetry as well as repeating compulsions. The "forbidden thoughts factor" correlated highly with intrusive and distressing thoughts of a violent, religious or sexual nature. The "cleaning factor" correlated highly with obsessions about contamination and compulsions related to cleaning. The "hoarding factor" only involved hoarding related obsessions and compulsions, and was identified as being distinct from other symptom groupings.

While OCD has been considered a homogenous disorder from a neuropsychological perspective, many of the putative neuropsychological deficits may be due to comorbid disorders. Furthermore, some subtypes have been associated with improvement in performance on certain tasks such as pattern recognition(washing subtype) and spatial working memory(obsessive thought subtype). Subgroups have also been distinguished by neuroimaging findings and treatment response. Neuroimaging studies on this have been too few, and the subtypes examined have differed too much to draw any conclusions. On the other hand, subtype dependent treatment response has been studied, and the hoarding subtype has consistently responded least to treatment.

Research by governments in Australia led to a universal definition for that country which appears to be the only research-based definition not to use diagnostic criteria: "Problem gambling is characterized by many difficulties in limiting money and/or time spent on gambling which leads to adverse consequences for the gambler, others, or for the community." The University of Maryland Medical Center defines pathological gambling as "being unable to resist impulses to gamble, which can lead to severe personal or social consequences".

Most other definitions of problem gambling can usually be simplified to any gambling that causes harm to the gambler or someone else in any way; however, these definitions are usually coupled with descriptions of the type of harm or the use of diagnostic criteria. The "DSM-V" has since reclassified pathological gambling as "gambling disorder" and has listed the disorder under substance-related and addictive disorders rather than impulse-control disorders. This is due to the symptomatology of the disorder resembling an addiction not dissimilar to that of substance-abuse. There are both environmental and genetic factors that can influence on gambler and cause some type of addiction. In order to be diagnosed, an individual must have at least four of the following symptoms in a 12-month period:

- Needs to gamble with increasing amounts of money in order to achieve the desired excitement

- Is restless or irritable when attempting to cut down or stop gambling

- Has made repeated unsuccessful efforts to control, cut back, or stop gambling

- Is often preoccupied with gambling (e.g., having persistent thoughts of reliving past gambling experiences, handicapping or planning the next venture, thinking of ways to get money with which to gamble)

- Often gambles when feeling distressed (e.g., helpless, guilty, anxious, depressed)

- After losing money gambling, often returns another day to get even ("chasing" one's losses)

- Lies to conceal the extent of involvement with gambling

- Has jeopardized or lost a significant relationship, job, education or career opportunity because of gambling

- Relies on others to provide money to relieve desperate financial situations caused by gambling

Some people with OCD exhibit what is known as "overvalued ideas". In such cases, the person with OCD will truly be uncertain whether the fears that cause them to perform their compulsions are irrational or not. After some discussion, it is possible to convince the individual that their fears may be unfounded. It may be more difficult to do ERP therapy on such people because they may be unwilling to cooperate, at least initially. There are severe cases in which the person has an unshakeable belief in the context of OCD that is difficult to differentiate from psychotic disorders.

Compulsive shopping or buying is characterized by a frequent irresistible urge to shop even if the purchases are not needed or cannot be afforded. The prevalence of compulsive buying in the U.S. has been estimated to be 2–8% of the general adult population, with 80–95% of these cases being females. The onset is believed to occur in late teens or early twenties and the disorder is considered to be generally chronic.

Kleptomania or klopemania is the inability to refrain from the urge for stealing items and is usually done for reasons other than personal use or financial gain. First described in 1816, kleptomania is classified in psychiatry as an impulse control disorder. Some of the main characteristics of the disorder suggest that kleptomania could be an obsessive-compulsive spectrum disorder.

The disorder is frequently under-diagnosed and is regularly associated with other psychiatric disorders, particularly anxiety and eating disorders, and alcohol and substance abuse. Patients with kleptomania are typically treated with therapies in other areas due to the comorbid grievances rather than issues directly related to kleptomania.

Over the last 100 years, a shift from psychotherapeutic to psychopharmacological interventions for kleptomania has occurred. Pharmacological treatments using selective serotonin reuptake inhibitors (SSRIs), mood stabilizers and opioid receptor antagonists, and other antidepressants along with cognitive behavioral therapy, have yielded positive results.

Problem gambling (or ludomania, but usually referred to as "gambling addiction" or "compulsive gambling") is an urge to gamble continuously despite harmful negative consequences or a desire to stop. Problem gambling is often defined by whether harm is experienced by the gambler or others, rather than by the gambler's behaviour. Severe problem gambling may be diagnosed as clinical pathological gambling if the gambler meets certain criteria. Pathological gambling is a common disorder that is associated with both social and family costs.

The "DSM-5" has re-classified the condition as an addictive disorder, with sufferers exhibiting many similarities to those who have substance addictions.

The term "gambling addiction" has long been used in the recovery movement. Pathological gambling was long considered by the American Psychiatric Association to be an impulse control disorder rather than an addiction. However, data suggest a closer relationship between pathological gambling and substance use disorders than exists between PG and obsessive-compulsive disorder, largely because the behaviors in problem gambling and most primary substance use disorders ("i.e.", those not resulting from a desire to "self-medicate" for another condition such as depression) seek to activate the brain's reward mechanisms while the behaviors characterizing obsessive-compulsive disorder are prompted by overactive and misplaced signals from the brain's fear mechanisms.

Problem gambling is an addictive behavior with a high comorbidity with alcohol problems. Comorbidity is the presence of one or more diseases or disorders co-occurring with each other. A common feature shared by people who suffer from gambling addiction is impulsivity.

Obsessive–compulsive personality disorder (OCPD) is a personality disorder characterized by a general pattern of concern with orderliness, perfectionism, excessive attention to details, mental and interpersonal control, and a need for control over one's environment, at the expense of flexibility, openness to experience, and efficiency. Workaholism and miserliness are also seen often in those with this personality disorder. Persons affected with this disorder may find it hard to relax, always feeling that time is running out for their activities, and that more effort is needed to achieve their goals. They may plan their activities down to the minute—a manifestation of the compulsive tendency to keep control over their environment and to dislike unpredictable things as things they cannot control.

The cause of OCPD is unknown. This is a distinct disorder from obsessive–compulsive disorder (OCD), and the relation between the two is contentious. Some (but not all) studies have found high comorbidity rates between the two disorders, and both may share outside similaritiesrigid and ritual-like behaviors, for example. Hoarding, orderliness, and a need for symmetry and organization are often seen in people with either disorder. Attitudes toward these behaviors differ between people affected with either of the disorders: for people with OCD, these behaviors are unwanted and seen as unhealthy, being the product of anxiety-inducing and involuntary thoughts, while for people with OCPD they are egosyntonic (that is, they are perceived by the subject as rational and desirable), being the result of, for example, a strong adherence to routines, a natural inclination towards cautiousness, or a desire to achieve perfection.

OCPD occurs in about 2–8% of the general population and 8–9% of psychiatric outpatients. The disorder occurs more often in men.

Body dysmorphic disorder is defined by an obsession with an imagined defect in physical appearance, and compulsive rituals in an attempt to conceal the perceived defect. Typical complaints include perceived facial flaws, perceived deformities of body parts and body size abnormalities. Some compulsive behaviors observed include mirror checking, ritualized application of makeup to hide the perceived flaw, excessive hair combing or cutting, excessive physician visits and plastic surgery. Body dysmorphic disorder is not gender specific and onset usually occurs in teens and young adults.

In psychology, relationship obsessive–compulsive disorder (ROCD) is a form of obsessive-compulsive disorder focusing on intimate relationships (whether romantic or non-romantic). Such obsessions can become extremely distressing and debilitating, having negative impacts on relationships functioning.

The following conditions have been hypothesized by various researchers as existing on the spectrum.

However, recently there is a growing support for proposals to narrow down this spectrum to only include body dysmorphic disorder, hypochondriasis, tic disorders, and trichotillomania.

Experts describe the spectrum of behaviors designated as addictive in terms of five interrelated concepts: patterns, habits, compulsions, impulse control disorders, and physical addiction.

Compulsive decluttering is a pattern of behavior that is characterized by an excessive desire to discard objects in one's home and living areas. Other terms for such behavior includes obsessive compulsive spartanism. The homes of compulsive declutterers are often empty. It is the antonym of compulsive hoarding.

An addictive personality refers to a particular set of personality traits that make an individual predisposed to developing addictions. This hypothesis states that there may be common personality traits observable in people suffering from addiction. Alan R. Lang of Florida State University, author of an addiction study prepared for the United States National Academy of Sciences, said, "If we can better identify the personality factors, they can help us devise better treatment and can open up new strategies to intervene and break the patterns of addiction."

Obsessive-compulsive disorder comprises thoughts, images or urges that are unwanted, distressing, interfere with a person's life and that are commonly experienced as contradicting a persons' beliefs and values. Such intrusive thoughts are frequently followed by compulsive behaviors aimed at "neutralizing" the feared consequence of the intrusions and temporarily relieve the anxiety caused by the obsessions. Attempts to suppress or "neutralize" obsessions increase rather than decrease the frequency and distress caused by the obsessions.

Common obsessive themes include fear of contamination, fears about being responsible for harming the self or others, doubts, and orderliness. However, people with OCD can also have religious and sexual obsessions. Some people with OCD may experience obsessions relating to the way they feel in an ongoing relationship or the way they felt in past relationships (ROCD). Repetitive thought about a person's feelings in intimate relationships may occur in the natural course of the relationship development; however, in ROCD such preoccupations are unwanted, intrusive, chronic and disabling.

An addictive behavior is a behavior, or a stimulus related to a behavior (e.g., sex or food), that is both rewarding and reinforcing, and is associated with the development of an addiction. Addictions involving addictive behaviors are normally referred to as behavioral addictions.

Whereas vanity involves a quest to aggrandize the appearance, BDD is experienced as a quest to merely normalize the appearance. Although delusional in about one of three cases, the appearance concern is usually nondelusional, an overvalued idea.

The bodily area of focus can be nearly any, yet is commonly face, hair, stomach, thighs, or hips. Some half dozen areas can be a roughly simultaneous focus. Many seek dermatological treatment or cosmetic surgery, which typically do not resolve the distress. On the other hand, attempts at self-treatment, as by skin picking, can create lesions where none previously existed.

BDD shares features with obsessive-compulsive disorder, but involves more depression and social avoidance. BDD often associates with social anxiety disorder. Some experience delusions that others are covertly pointing out their flaws. Cognitive testing and neuroimaging suggest both a bias toward detailed visual analysis and a tendency toward emotional hyperarousal.

Most generally, one experiencing BDD ruminates over the perceived bodily defect up to several hours daily, uses either social avoidance or camouflaging with cosmetics or apparel, repetitively checks the appearance, compares it to that of other persons, and might often seek verbal reassurances. One might sometimes avoid mirrors, repetitively change outfits, groom excessively, or restrict eating.

BDD's severity can wax and wane, and flareups tend to yield absences from school, work, or socializing, sometimes leading to protracted social isolation, with some becoming housebound for extended periods. Social impairment is usually greatest, sometimes approaching avoidance of all social activities. Poor concentration and motivation impair academic and occupational performance. The distress of BDD tends to exceed that of either major depressive disorder or type-2 diabetes, and rates of suicidal ideation and attempts are especially high.