Many people experience the type of bad or unwanted thoughts that people with more troubling intrusive thoughts have, but most people can dismiss these thoughts. For most people, intrusive thoughts are a "fleeting annoyance". Psychologist Stanley Rachman presented a questionnaire to healthy college students and found that virtually all said they had these thoughts from time to time, including thoughts of sexual violence, sexual punishment, "unnatural" sex acts, painful sexual practices, blasphemous or obscene images, thoughts of harming elderly people or someone close to them, violence against animals or towards children, and impulsive or abusive outbursts or utterances. Such bad thoughts are universal among humans, and have "almost certainly always been a part of the human condition".

When intrusive thoughts occur with obsessive-compulsive disorder (OCD), patients are less able to ignore the unpleasant thoughts and may pay undue attention to them, causing the thoughts to become more frequent and distressing. The thoughts may become obsessions which are paralyzing, severe, and constantly present, and can range from thoughts of violence or sex to religious blasphemy. Distinguishing them from normal intrusive thoughts experienced by many people, the intrusive thoughts associated with OCD may be anxiety provoking, irrepressible, and persistent.

How people react to intrusive thoughts may determine whether these thoughts will become severe, turn into obsessions, or require treatment. Intrusive thoughts can occur with or without compulsions. Carrying out the compulsion reduces the anxiety, but makes the urge to perform the compulsion stronger each time it recurs, reinforcing the intrusive thoughts. According to Lee Baer, suppressing the thoughts only makes them stronger, and recognizing that bad thoughts do not signify that one is truly evil is one of the steps to overcoming them. There is evidence of the benefit of acceptance as an alternative to suppression of intrusive thoughts. A study showed that those instructed to suppress intrusive thoughts experienced more distress after suppression, while patients instructed to accept the bad thoughts experienced decreased discomfort. These results may be related to underlying cognitive processes involved in OCD. However, accepting the thoughts can be more difficult for persons with OCD. In the 19th century, OCD was known as "the doubting sickness"; the "pathological doubt" that accompanies OCD can make it harder for a person with OCD to distinguish "normal" intrusive thoughts as experienced by most people, causing them to "suffer in silence, feeling too embarrassed or worried that they will be thought crazy".

The possibility that most patients suffering from intrusive thoughts will ever act on those thoughts is low. Patients who are experiencing intense guilt, anxiety, shame, and upset over these thoughts are different from those who actually act on them. The history of violent crime is dominated by those who feel no guilt or remorse; the very fact that someone is tormented by intrusive thoughts and has never acted on them before is an excellent predictor that they will not act upon the thoughts. Patients who are not troubled or shamed by their thoughts, do not find them distasteful, or who have actually taken action, might need to have more serious conditions such as psychosis or potentially criminal behaviors ruled out. According to Lee Baer, a patient should be concerned that intrusive thoughts are dangerous if the person does not feel upset by the thoughts, or rather finds them pleasurable; has ever acted on violent or sexual thoughts or urges; hears voices or sees things that others do not see; or feels uncontrollable irresistible anger.

Intrusive thoughts may involve violent obsessions about hurting others or themselves. They can be related to primarily obsessional obsessive compulsive disorder. These thoughts can include harming a child; jumping from a bridge, mountain, or the top of a tall building; urges to jump in front of a train or automobile; and urges to push another in front of a train or automobile. Rachman's survey of healthy college students found that virtually all of them had intrusive thoughts from time to time, including:

- causing harm to elderly people

- imagining or wishing harm upon someone close to oneself

- impulses to violently attack, hit, harm or kill a person, small child, or animal

- impulses to shout at or abuse someone, or attack and violently punish someone, or say something rude, inappropriate, nasty, or violent to someone.

These thoughts are part of being human, and need not ruin quality of life. Treatment is available when the thoughts are associated with OCD and become persistent, severe, or distressing.

A variant of aggressive intrusive thoughts is L'appel du vide, or the call of the void. Sufferers of "L'appel du vide" generally describe the condition as manifesting in certain situations, normally as a wish or brief desire to jump from a high location.

The DSM-5 diagnostic criteria for hoarding disorder are:

Understanding the age of onset of hoarding behavior can help develop methods of treatment for this “substantial functional impairment”. Hoarders pose danger to not only themselves, but others as well. The prevalence of compulsive hoarding in the community has been estimated at between 2% and 5%, significantly higher than the rates of OCD, panic disorder, schizophrenia, and other disorders.

751 people were chosen for a study in which people self-reported their hoarding behavior. Of these individuals, most reported the onset of their hoarding symptoms between the ages of 11 and 20 years old, with 70% reporting the behaviors before the age of 21. Fewer than 4% of people reported the onset of their symptoms after the age of 40. The data shows that compulsive hoarding usually begins early, but often does not become more prominent until after age 40. Different reasons have been given for this, such as the prominence of family presence early in life and the extent of limits and facilitates they have on removing clutter. The understanding of early onset hoarding behavior may help in the future to better distinguish hoarding behavior from “normal” childhood collecting behaviors.

A second key part of this study was to determine if stressful life events are linked to the onset of hoarding symptoms. Similar to self-harming, traumatized persons may create "a problem" for themselves in order to avoid their real anxiety or trauma. Facing their real issues may be too difficult for them, so they "create" a kind of "artificial" problem (in their case, hoarding) and prefer to battle with it rather than determine, face, or do something about their real anxieties. Hoarders may suppress their psychological pain by "hoarding." The study shows that adults who hoard report a greater lifetime incidence of having possessions taken by force, forced sexual activity as either an adult or a child, including forced intercourse, and being physically handled roughly during childhood, thus proving traumatic events are positively correlated with the severity of hoarding. For each five years of life the participant would rate from 1 to 4, 4 being the most severe, the severity of their hoarding symptoms. Of the participants, 548 reported a chronic course, 159 an increasing course and 39 people, a decreasing course of illness. The incidents of increased hoarding behavior were usually correlated to five categories of stressful life events.

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

Primarily cognitive obsessive-compulsive disorder (also commonly called "primarily obsessional OCD", purely obsessional OCD, Pure-O, OCD without overt compulsions or with covert compulsions) is a lesser-known form or manifestation of OCD. For people with primarily obsessional OCD, there are fewer observable compulsions, compared to those commonly seen with the typical form of OCD (checking, counting, hand-washing, etc.). While ritualizing and neutralizing behaviors do take place, they are mostly cognitive in nature, involving mental avoidance and excessiverumination. Primarily obsessional OCD often takes the form of intrusive thoughts of a distressing or violent nature.

The core symptom of depersonalization-derealization disorder is the subjective experience of "unreality in one's self", or detachment from one's surroundings. People who are diagnosed with depersonalization also experience an urge to question and think critically about the nature of reality and existence.

Individuals who experience depersonalization can feel divorced from their own personal physicality by sensing their body sensations, feelings, emotions and behaviors as not belonging to themselves. As such, a recognition of one's self breaks down. Depersonalization can result in very high anxiety levels, which can intensify these perceptions even further.

Individuals with depersonalization describe feeling disconnected from their physicality; feeling as if they are not completely occupying their own body; feeling as if their speech or physical movements are out of their control; feeling detached from their own thoughts or emotions; and experiencing themselves and their lives from a distance. While depersonalization involves detachment from one's "self", individuals with derealization feel detached from their "surroundings", as if the world around them is foggy, dreamlike, or visually distorted. Some people with depersonalization disorder also have visual alterations such as rapid fluctuations in light. While the exact cause of these perceptual changes has not been determined, it is thought that they may be due to previous drug use. These perceptual changes differ from true hallucinatory phenomena, as they are closer to being optical distortions or illusions rather than psychotic breaks from reality. Individuals with the disorder commonly describe a feeling as though time is "passing" them by and they are not in the notion of the present. These experiences which strike at the core of a person's identity and consciousness may cause a person to feel uneasy or anxious.

Factors that tend to diminish symptoms are comforting personal interactions, intense physical or emotional stimulation, and relaxation. Distracting oneself (by engaging in conversation or watching a movie, for example) may also provide temporary relief. Some other factors that are identified as relieving symptom severity are diet and/or exercise, while alcohol and fatigue are listed by some as worsening their symptoms.

First experiences with depersonalization may be frightening, with patients fearing loss of control, dissociation from the rest of society and functional impairment. The majority of people with depersonalization-derealization disorder misinterpret the symptoms, thinking that they are signs of serious psychosis or brain dysfunction. This commonly leads to an increase of anxiety experienced by the patient, and obsession, which contributes to the worsening of symptoms.

Occasional, brief moments of mild depersonalization can be experienced by many members of the general population; however, depersonalization-derealization disorder occurs when these feelings are strong, severe, persistent, or recurrent and when these feelings interfere with daily functioning.

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.

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.

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.

Depersonalization disorder (DPD), also known as depersonalization/derealization disorder, is a mental disorder in which the person has persistent or recurrent feelings of depersonalization or derealization. Symptoms can be classified as either depersonalization or derealization. Depersonalization is described as feeling disconnected or estranged from one's self. Individuals experiencing depersonalization may report feeling as if they are an outside observer of their own thoughts or body, and often report feeling a loss of control over their thoughts or actions. In some cases, individuals may be unable to accept their reflection as their own, or they may have out-of-body experiences. While depersonalization is a sense of detachment from one's self, derealization is described as detachment from one's surroundings. Individuals experiencing derealization may report perceiving the world around them as foggy, dreamlike/surreal, or visually distorted. In addition to these depersonalization-derealization disorder symptoms, the inner turmoil created by the disorder can result in depression, self-harm, low self-esteem, panic attacks, phobias, etc. It can also cause a variety of physical symptoms, including chest pain, blurry vision, visual snow, nausea, and the sensation of pins and needles in one's arms or legs.

Depersonalization-derealization disorder is thought to be caused largely by severe traumatic lifetime events, including childhood abuse, accidents, natural disasters, war, torture, and bad drug experiences. It is unclear whether genetics plays a role; however, there are many neurochemical and hormonal changes in individuals with depersonalization disorder. The disorder is typically associated with cognitive disruptions in early perceptual and attentional processes.

Diagnostic criteria for depersonalization-derealization disorder include, among other symptoms, persistent or recurrent feelings of detachment from one's mental or bodily processes or from one's surroundings. A diagnosis is made when the dissociation is persistent and interferes with the social and/or occupational functions of daily life. However, accurate descriptions of the symptoms are hard to provide due to the subjective nature of depersonalization/derealization and persons' ambiguous use of language when describing these episodes. In the DSM-5, it was combined with Derealization Disorder and renamed Depersonalization/Derealization Disorder (DDPD). In the DSM-5, it remains classified as a dissociative disorder, while the ICD-10 calls it depersonalization-derealization syndrome and classifies it as a neurotic disorder. Although the disorder is an alteration in the subjective experience of reality, it is not a form of psychosis, as the person is able to distinguish between their own internal experiences and the objective reality of the outside world. During episodic and continuous depersonalization, the person can distinguish between reality and fantasy. In other words, the grasp on reality remains stable at all times.

While depersonalization-derealization disorder was once considered rare, lifetime experiences with it occur in about 1–2% of the general population. The chronic form of the disorder has a reported prevalence of 0.8 to 1.9%. While these numbers may seem small, depersonalization/derealization experiences have been reported by a majority of the general population, with varying degrees of intensity. While brief episodes of depersonalization or derealization can be common in the general population, the disorder is only diagnosed when these symptoms cause substantial distress or impair social, occupational, or other important areas of functioning.

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."

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.

Quality of life is reduced across all domains in OCD. While psychological or pharmacological treatment can lead to a reduction of OCD symptoms and an increase in QoL, symptoms may persist at moderate levels even following adequate treatment courses, and completely symptom-free periods are uncommon. In pediatric OCD, around 40% still have the disorder in adulthood, and around 40% qualify for remission.

In scrupulosity, a person's obsessions focus on moral or religious fears, such as the fear of being an evil person or the fear of divine retribution for sin. Although it can affect nonreligious people, it is usually related to religious beliefs. In the strict sense, not all obsessive–compulsive behaviors related to religion are instances of scrupulosity: strictly speaking, for example, scrupulosity is not present in people who repeat religious requirements merely to be sure that they were done properly.

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.

Sexual obsessions are obsessions with sexual activity. In the context of obsessive-compulsive disorder (OCD), these are extremely common, and can become extremely debilitating, making the person ashamed of the symptoms and reluctant to seek help. As preoccupation with sexual matters, however, does not only occur as a symptom of OCD, they may be enjoyable in other contexts (i.e. sexual fantasy).

Scrupulosity is characterized by pathological guilt about moral or religious issues. It is personally distressing, objectively dysfunctional, and often accompanied by significant impairment in social functioning. It is typically conceptualized as a moral or religious form of obsessive–compulsive disorder (OCD), although this categorization is empirically disputable.

The term is derived from the Latin "scrupulum", a sharp stone, implying a stabbing pain on the conscience. Scrupulosity was formerly called "scruples" in religious contexts, but the word "scruples" now commonly refers to a troubling of the conscience rather than to the disorder.

As a personality trait, scrupulosity is a recognized diagnostic criterion for obsessive–compulsive personality disorder. It is sometimes called "scrupulousness", but that word properly applies to the positive trait of having scruples.

Many different types of medication can create/induce pure OCD in patients that have never had symptoms before. A new chapter about OCD in the DSM-5 (2013) now specifically includes drug-induced OCD.

Second generation atypical anti-psychotics, such as Olanzapine (Zyprexa), have been proven to induce de-novo OCD in patients.

Perfectionism, in psychology, is a personality trait characterized by a person's striving for flawlessness and setting high performance standards, accompanied by critical self-evaluations and concerns regarding others' evaluations. It is best conceptualized as a multidimensional characteristic, as psychologists agree that there are many positive and negative aspects. In its maladaptive form, perfectionism drives people to attempt to achieve an unattainable ideal, while their adaptive perfectionism can sometimes motivate them to reach their goals. In the end, they derive pleasure from doing so. When perfectionists do not reach their goals, they often fall into depression.

The single largest category of anxiety disorders is that of specific phobias which includes all cases in which fear and anxiety are triggered by a specific stimulus or situation. Between 5% and 12% of the population worldwide suffer from specific phobias. Sufferers typically anticipate terrifying consequences from encountering the object of their fear, which can be anything from an animal to a location to a bodily fluid to a particular situation. Common phobias are flying, blood, water, highway driving, and tunnels. When people are exposed to their phobia, they may experience trembling, shortness of breath, or rapid heartbeat. People understand that their fear is not proportional to the actual potential danger but still are overwhelmed by it.

Generalized anxiety disorder (GAD) is a common disorder, characterized by long-lasting anxiety that is not focused on any one object or situation. Those suffering from generalized anxiety disorder experience non-specific persistent fear and worry, and become overly concerned with everyday matters. Generalized anxiety disorder is "characterized by chronic excessive worry accompanied by three or more of the following symptoms: restlessness, fatigue, concentration problems, irritability, muscle tension, and sleep disturbance". Generalized anxiety disorder is the most common anxiety disorder to affect older adults. Anxiety can be a symptom of a medical or substance abuse problem, and medical professionals must be aware of this. A diagnosis of GAD is made when a person has been excessively worried about an everyday problem for six months or more. A person may find that they have problems making daily decisions and remembering commitments as a result of lack of concentration/preoccupation with worry. Appearance looks strained, with increased sweating from the hands, feet, and axillae, and they may be tearful, which can suggest depression. Before a diagnosis of anxiety disorder is made, physicians must rule out drug-induced anxiety and other medical causes.

In children GAD may be associated with headaches, restlessness, abdominal pain, and heart palpitations. Typically it begins around 8 to 9 years of age.

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.

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.

Those suffering from primarily obsessional OCD might appear normal and high-functioning, yet spend a great deal of time ruminating, trying to solve or answer any of the questions that cause them distress. Very often, Pure O sufferers are dealing with considerable guilt and anxiety. Ruminations may include trying to think about something 'in the right way' in an attempt to relieve this distress.

For example, an intrusive thought "I could just kill Bill with this steak knife" is followed by a catastrophic misinterpretation of the thought, i.e. "How could I have such a thought? Deep down, I must be a psychopath." This might lead a person to continually surf the Internet, reading numerous articles on defining psychopathy. This reassurance-seeking ritual will, ironically, provide no further clarification and could exacerbate the intensity of the search for the answer. There are numerous corresponding cognitive biases present, including thought-action fusion, over-importance of thoughts, and need for control over thoughts.

Despite how real and imposing the intrusive thoughts may be to an individual, the sufferer will probably never carry out actions related to these thoughts, even if one believes themselves capable of doing so. One of the reasons for this is because the person in question will go to extreme lengths to avoid circumstances which could trigger their intrusive thoughts.

The disorder is particularly easy to miss by many well-trained clinicians, as it closely resembles markers of generalized anxiety disorder and does not include observable, compulsive behaviors. Clinical "success" is reached when the sufferer becomes indifferent to the need to answer the question. While many clinicians will mistakenly offer reassurance and try to help their patient achieve a definitive answer (an unfortunate consequence of therapists treating primarily obsessional OCD as generalized anxiety disorder), this method only contributes to the intensity or length of the patient's rumination, as the neuropathways of the OCD brain will predictably come up with creative ways to "trick" the person out of reassurance, negating any temporary relief and perpetuating the cycle of obsessing.

The most effective treatment for primarily obsessional OCD appears to be cognitive-behavioral therapy. (more specifically exposure and response prevention (ERP)) as well as cognitive therapy (CT) which may or may not be combined with the use of medication, such as SSRIs. People suffering from OCD without overt compulsions are considered by some researchers more refractory towards ERP compared to other OCD sufferers and therefore ERP can prove less successful than CT.

ERP of Pure-O is theoretically based on the principles of classical conditioning and extinction. The spike often presents itself as a paramount question or disastrous scenario. A response that answers the spike in a way that leaves ambiguity is sometimes warranted. "If I don't remember what I had for breakfast yesterday my mother will die of cancer!" Using the antidote procedure, a cognitive response would be one in which the subject accepts this possibility and is willing to take the risk of his mother dying of cancer or the question recurring for eternity. No effort is expended in directly answering the question in an effort to find resolution. In another example, the spike would be, "Maybe I said something offensive to my boss yesterday." A recommended response would be, "Maybe I did. I'll live with the possibility and take the risk he'll fire me tomorrow." Using this procedure, it is imperative that the distinction be made between the therapeutic response and rumination. The therapeutic response does not seek to answer the question but to accept the uncertainty of the unsolved dilemma.

Acceptance and commitment therapy (ACT) is a newer approach that also is used to treat purely obsessional OCD, as well as other mental disorders such as anxiety and clinical depression. Mindfulness-based stress reduction (MBSR) may also be helpful for breaking out of the ruminative thinking process.