There is evidence that narcissistic personality disorder is heritable, and individuals are much more likely to develop NPD if they have a family history of the disorder. Studies on the occurrence of personality disorders in twins determined that there is a moderate to high heritability for narcissistic personality disorder.

However the specific genes and gene interactions that contribute to its cause, and how they may influence the developmental and physiological processes underlying this condition, have yet to be determined.

Environmental and social factors are also thought to have a significant influence on the onset of NPD. In some people, pathological narcissism may develop from an impaired attachment to their primary caregivers, usually their parents. This can result in the child's perception of himself/herself as unimportant and unconnected to others. The child typically comes to believe they have some personality defect that makes them unvalued and unwanted. Overindulgent, permissive parenting as well as insensitive, over-controlling parenting, are believed to be contributing factors.

According to Leonard Groopman and Arnold Cooper, the following factors have been identified by various researchers as possible factors that promote the development of NPD:

- An oversensitive temperament (personality traits) at birth.

- Excessive admiration that is never balanced with realistic feedback.

- Excessive praise for good behaviors or excessive criticism for bad behaviors in childhood.

- Overindulgence and overvaluation by parents, other family members, or peers.

- Being praised for perceived exceptional looks or abilities by adults.

- Severe emotional abuse in childhood.

- Unpredictable or unreliable caregiving from parents.

- Learning manipulative behaviors from parents or peers.

- Valued by parents as a means to regulate their own self-esteem.

Cultural elements are believed to influence the prevalence of NPD as well since NPD traits have been found to be more common in modern societies than in traditional ones.

A fixed fantasy — also known as a "dysfunctional schema" — is a belief or system of beliefs held by a single individual to be genuine, but that cannot be verified in reality. The term is typically applied to individuals suffering from some type of psychiatric dysregulation, most often a personality disorder.

The term is also used in the different context of psychoanalysis to distinguish between 'a normal transitory one and a fixed fantasy' with respect to the phantasised 'fulfilment in conscious or unconscious thought of the sexualised wish'.

Otherkin largely identify as mythical creatures, with others identifying as creatures from fantasy or popular culture. Examples include: angels, demons, dragons, goats, elves, fairies, sprites, aliens, and cartoon characters. Many otherkin believe in the existence of a multitude of parallel universes, and their belief in the existence of supernatural or sapient non-human beings is grounded in that idea.

With regards to their online communities, otherkin largely function without formal authority structures, and mostly focus on support and information gathering, often dividing into more specific groups based on kintype. There are occasional offline gatherings, but the otherkin network is mostly an online phenomenon.

Some otherkin (such as elvenkin) state they are allergic to iron (and products of modern technology), while others (such as dragonkin) state that having no allergies is a sign of otherkin condition. Some otherkin also claim to be especially empathic and attuned to nature. Some state to be able to shapeshift mentally or astrally, meaning that they experience the sense of being in their particular form while not actually changing physically.

The therian and vampire subcultures are related to the otherkin community, and are considered part of it by most otherkin, but are culturally and historically distinct movements of their own, despite some overlap in membership.

Otherkin are a subculture who socially and spiritually identify as partially or entirely non-human. Some of them surmise that they are, either spiritually or genetically, not human; however, this claim is unsubstantiated. This is explained by some members of the otherkin community as possible through reincarnation, having a non-human soul, ancestry, or symbolic metaphor. Some scholars categorize this identity claim as "religious", because it is largely based on supernatural beliefs. Adherents more typically deny the religiosity of otherkinism, referring to it instead as simply a congenital condition, or a metaphysical state of being.

Studies of borderline children often uncovered at the base of their self-destructive behaviour patterns ' a "fixed fantasy"...a rigid, nonreflective scenario of self-induced pain'. As part of a psychic defence mechanism, 'the omnipotence betrayed by the "fixed fantasy" underlying self-victimization or other forms of self-defeating behaviour...creates the illusory sense that they are actively producing the abandonment [&] pain', rather than merely suffering it passively - 'arranging deceits..arrang[ing] for blows to fall'. Unfortunately 'in the course of development, these patterns acquire multiple adaptive functions...and serve as a key organizer of their sense of self'.

'In producing movement away from fixed fantasy systems, commonplace statements are often necessary because the more fixed and extensive the fantasy system, the fewer the transitional opportunities offered; there is little conflicting material to ride. Banalities may be the only resource', as anything more complex may be used to feed back into the fantasy system itself.

Money disorders are the maladaptive patterns of financial beliefs and behaviors that lead to clinically significant distress, impairment in social or occupational functioning, due to financial strain or an inability to appropriately enjoy one’s financial resources. With the exception of pathological gambling and compulsive buying, psychology and the mental health fields have largely neglected dysfunctional money disorders. The term is contentious among mental health professionals and as of 2017, money disorder is not a clinical diagnosis in either the DSM or ICD medical classifications of diseases and medical disorders.

Types of behaviors, or “scripts”, related to money disorders include money avoidance, money worship, money status and money vigilance. Some mental health practitioners say that those afflicted with money disorders or who have problematic money beliefs can seek financial therapy. With financial therapy, financial planners and relationship therapists work together to provide comprehensive treatment to clients experiencing financial distress.

Some scholars believe that codependency is not a negative trait, and does not need to be treated, as it is more likely a healthy personality trait taken to excess. Codependency in nonclinical populations has some links with favourable characteristics of family functioning.

Stan Katz states that codependence is over-diagnosed, and that many people who could be helped with shorter-term treatments instead become dependent on long-term self-help programs. The language of, symptoms of, and treatment for codependence derive from the medical model suggesting a disease process underlies the behavior. However, there is no evidence that codependence is caused by a disease process.

In their book, “Attached.”, Dr. Amir Levine and Rachel S. F. Heller, address what they call the “codependency myth” by asserting that attachment theory is a more scientific and helpful model for understanding and dealing with attachment in adults.

Codependency is a type of dysfunctional helping relationship where one person supports or enables another person's drug addiction, alcoholism, gambling addiction, poor mental health, immaturity, irresponsibility, or under-achievement. Among the core characteristics of codependency, the most common theme is an excessive reliance on other people for approval and a sense of identity.

Given its grassroots origin, the precise definition of codependency varies based on the source but can be generally characterized as a subclinical and situational or episodic behavior similar to that of dependent personality disorder. In its broadest definition, a codependent is someone who cannot function from their innate self and whose thinking and behavior is instead organized around another person, or even a process, or substance. In this context, people who are addicted to a substance, like drugs, or a process, like gambling or sex, can also be considered codependent. In its most narrow definition, it requires one person to be physically or psychologically addicted, such as to heroin, and the second person to be psychologically dependent on that behavior. Some users of the codependency concept use the word as an alternative to using the concept of dysfunctional families, without statements that classify it as a disease.

Estimates of the percentage of female sexual dysfunction attributable to physical factors have ranged from 30% to 80%. The disorders most likely to result in sexual dysfunction are those that lead to problems in circulatory or neurological function. These factors have been more extensively explored in men than in women. Physical etiologies such as neurological and cardiovascular illnesses have been directly implicated in both premature and retarded ejaculation as well as in erectile disorder, but the contribution of physiological factors to female sexual dysfunction is not so clear. However, recent literature does suggest that there may be an impairment in the arousal phase among diabetic women. Given that diabetic women show a significant variability in their response to this medical disorder, it is not surprising that the disease’s influence on arousal is also highly variable. In fact, the lack of a clear association between medical disorders and sexual functioning suggests that psychological factors play a significant part in the impact of these disorders on sexual functioning.

Kenneth Maravilla, Professor of Radiology and Neurological Surgery and Director of MRI Research Laboratory at the University of Washington, Seattle, presented research findings based on neuro-imaging of women's sexual function. In a small pilot study of four women with female sexual arousal disorder, Maravilla reported there was less brain activation seen in this group, including very little activation in the amygdala. These women also showed increased activation in the temporal areas, in contrast to women without sexual difficulties, who showed deactivation in similar areas. This may suggest an increased level of inhibition with an arousal stimulus in this small group of women with FSAD.

Several types of medications, including selective serotonin reuptake inhibitors (SSRIs), can cause sexual dysfunction and in the case of SSRI and SNRI, these dysfunctions may become permanent after the end of the treatment.

A number of studies have explored the factors that contribute to female sexual arousal disorder and female orgasmic disorder. These factors include both psychological and physical factors. Psychologically, possible causes of the disorder include the impact of childhood and adolescence experiences and current events – both within the individual and within the current relationship.

Low frustration tolerance (LFT), or "short-term hedonism" is a concept utilized to describe the inability to tolerate unpleasant feelings or stressful situations. It stems from the feeling that reality should be as wished, and that any frustration should be resolved quickly and easily. People with low frustration tolerance experience emotional disturbance when frustrations are not quickly resolved. Behaviors are then directed towards avoiding frustrating events which, paradoxically, leads to increased frustration and even greater mental stress.

In REBT the opposite construct is "high frustration tolerance".

As it has already been mentioned, the organic personality disorder is included in a wide group of personality and behavioural disorders. This mental health disorder can be caused by disease, brain damages or dysfunctions in specific brain areas in frontal lobe. The most common reason for this profound change in personality is the traumatic brain injury (TBI). Children, whose brain areas have injured or damaged, may present Attention Deficit Hyperactivity Disorder (ADHD), oppositional defiant disorder (ODD) and organic personality disorder. Moreover, this disorder is characterised as "frontal lobe syndrome". This characteristic name shows that the organic personality disorder can usually be caused by lesions in three brain areas of frontal lobe. Specifically, the symptoms of organic personality disorder can also be caused by traumatic brain injuries in orbitofrontal cortex, anterior cingulate cortex and dorsolateral prefrontal cortex. It is worth to be mentioned that organic personality disorder may also be caused by lesions in other circumscribed brain areas.

As it has already been mentioned, patients with organic personality disorder show a wide variety of sudden behavioural changes and dysfunctions. There are not a lot of information about the treatment of this mental health disorder. The pharmacological approach is the most common therapy among patients with organic personality disorder. However, the choice of drug therapy relies on the seriousness of patient's situation and what symptoms are shown. The choice and administration of specific drugs contribute to the reduction of symptoms of organic personality disorder. For this reason, it is crucial for patients' treatment to be assessed by clinical psychologists and psychiatrists before the administration of drug.

Additionally, the dysfunctions in expression of behaviour of patients with organic personality disorder and the development of symptom of irritability, which are caused by aggressive and self-injurious behaviours, can be dealt with the administration of carbamazepine. Moreover, the symptoms of this disorder can be decreased by the administration of valproic acid. Also, emotional irritability and signs of depression can be dealt with the use of nortriptyline and low-dose thioridazine. Except from the symptom of irritability, patients express aggressive behaviours. At the onset of drug therapy for effective treatment of anger and aggression, the drug of carbamazepine, phenobarbital, benztropine and haloperidol can be administrated in order to reduce the symptoms of patients with organic personality disorder. In addition, the use of propranolol may decrease the frequent behaviours of rage attacks.

Finally, it is important for patients to take part in psychotherapy sessions during the period of drug therapy. In this way, there is prevention and patients can be protected by negative effects of drugs on their organism and their behaviour. Furthermore, the clinicians can provide useful and helpful support to patients during these psychotherapy sessions. Thus, the combination of drug therapy with psychotherapy can lead to the reduction of symptoms of this disorder and the improvement of patients' situation.

A spoiled child, spoiled brat, or simply a brat is a derogatory term aimed at children who exhibit behavioral problems from being overindulged by their parents. Children and teens who are perceived as spoiled may be described as "overindulged", "grandiose", "narcissistic" or "egocentric-regressed". Perception is important to take into account, because when the child has a neurological condition such as autism, ADHD or intellectual disability, observers may judge them as "spoiled" without understanding the whole picture. There is no accepted scientific definition of what "spoiled" means, and professionals are often unwilling to use the label because it is considered vague and derogatory. Being spoiled is not recognized as a mental disorder in any of the medical manuals, such as the ICD-10 or the DSM-IV, or its successor, the DSM-5.

Richard Weaver, in his work "Ideas Have Consequences", introduced the term “spoiled child psychology” in 1948. In 1989, Bruce McIntosh coined the term the "spoiled child syndrome". The syndrome is characterized by "excessive, self-centered, and immature behavior". It includes lack of consideration for other people, recurrent temper tantrums, an inability to handle the delay of gratification, demands for having one's own way, obstructiveness, and manipulation to get their way. McIntosh attributed the syndrome to "the failure of parents to enforce consistent, age-appropriate limits", but others, such as Aylward, note that temperament is probably a contributory factor. It is important to note that the temper tantrums are "recurrent". McIntosh observes that "many of the problem behaviors that cause parental concern are unrelated to spoiling as properly understood". Children may have occasional temper tantrums without them falling under the umbrella of "spoiled". Extreme cases of spoiled child syndrome, in contrast, will involve "frequent" temper tantrums, physical aggression, defiance, destructive behavior, and refusal to comply with even the simple demands of daily tasks. This can be similar to the profile of children diagnosed with Pathological Demand Avoidance, which is part of the autism spectrum.

Multiple complex developmental disorder is likely to be caused by a number of different various genetic factors. Each individual with MCDD is unique from one another and displays different symptoms. Various neuropsychological disorders can also be found in family members of people with MCDD.

The frustration discomfort scale (FDS), a multidimensional measure for LFT, was developed using REBT theories.

These dimensions were labelled in four categories:

1. Emotional intolerance, involving intolerance of emotional distress.

2. Entitlement, involving intolerance of unfairness and frustrated gratification.

3. Discomfort intolerance, involving intolerance of difficulties and hassles.

4. Achievement, involving intolerance of frustrated achievement goals.

Multiple complex developmental disorder (MCDD) is a research category, proposed to involve several neurological and psychological symptoms where at least some symptoms are first noticed during early childhood and persist throughout life. It was originally suggested to be a subtype of autistic spectrum disorders (PDD) with co-morbid schizophrenia or another psychotic disorder; however, there is some controversy that not everyone with MCDD meets criteria for both PDD and psychosis. The term "multiplex developmental disorder" was coined by Donald J. Cohen in 1986.

Tactile hallucination is the false perception of tactile sensory input that creates a hallucinatory sensation of physical contact with an imaginary object. It is caused by the faulty integration of the tactile sensory neural signals generated in the spinal cord and the thalamus and sent to the primary somatosensory cortex (SI) and secondary somatosensory cortex (SII). Tactile hallucinations are recurrent symptoms of neurological diseases such as schizophrenia, Parkinson's disease, Ekbom's syndrome and delerium tremens. Patients who experience phantom limb pains also experience a type of tactile hallucination. Tactile hallucinations are also caused by drugs such as cocaine and alcohol.

A few possible explanations for anosodiaphoria exist:

1. The patient is aware of the deficit but does not fully comprehend it or its significance for functioning

2. May be related to an affective communication disorder and defective arousal. These emotional disorders cannot account for the verbal explicit denial of illness of anosognosia.

Other explanations include reduced emotional experience, impaired emotional communication, alexithymia, behavioral abnormalities, dysexecutive syndrome, and the frontal lobes.

Indifference to illness may have an adverse impact on a patient's engagement in neurological rehabilitation, cognitive rehabilitation and physical rehabilitation. Patients are not likely to implement rehabilitation for a condition about which they are indifferent. Although anosognosia often resolves in days to weeks after stroke, anosodiaphoria often persists. Therefore, the therapist has to be creative in their rehabilitation approach in order to maintain the interest of the patient.

Ideational apraxia (IA) is a neurological disorder which explains the loss of ability to conceptualize, plan, and execute the complex sequences of motor actions involved in the use of tools or otherwise interacting with objects in everyday life. Ideational apraxia is a condition in which an individual is unable to plan movements related to interaction with objects, because he has lost the perception of the object's purpose. Characteristics of this disorder include a disturbance in the concept of the sequential organization of voluntary actions. The patient appears to have lost the knowledge or thought of what an object represents. This disorder was first seen 100 years ago by Doctor Arnold Pick, who described a patient who appeared to have lost their ability to use objects. The patient would make errors such as combing their hair with the wrong side of the comb or placing a pistol in his mouth. From that point on, several other

researchers and doctors have stumbled upon this unique disorder. IA has been described under several names such as, agnosia of utilization, conceptual apraxia or loss of knowledge about the use of tools, or semantic amnesia of tool usage. The term apraxia was first created by Steinthal in 1871 and was then applied by Gogol, Kusmaul, Star, and Pick to patients who failed to pantomime the use of tools. It was not until the 1900s, when Liepmann refined the definition, that it specifically described disorders that involved motor planning, rather than disturbances in the patient’s visual perception, language, or symbolism.

Due to the subjective nature of autotopagnosia, there are many hypotheses presented as to the underlying causation. Since the condition by definition is an inability to recognize the human body and its parts, the disorder could stem from a language deficit specific to body parts. On the other hand, the patient could suffer from a disrupted body image or a variation of the inability to separate parts from whole. It is also believed that autotopagnosia has multiple underlying causes that cannot be categorized as either language-specific or body-image-specific. The rarity of autotopagnosia, frequently combined with the manifestation of other psychoneurological disorders, makes the prime cause extremely difficult to study. In many cases, one of these accompanying conditions—often aphasia—could be masking the patient’s autotopagnosia altogether.

Autotopagnosia from the Greek "a" and "gnosis," meaning "without knowledge", "topos" meaning "place", and "auto" meaning "oneself", autotopagnosia virtually translates to the "lack of knowledge about one's own space," and is clinically described as such.

Autotopagnosia is a form of agnosia, characterized by an inability to localize and orient different parts of the body. The psychoneurological disorder has also been referred to as "body-image agnosia" or "somatotopagnosia." "Somatotopagnosia" has been argued to be a better suited term to describe the condition. While autotopagnosia emphasizes the deficiencies in localizing only one's own body parts and orientation, "somatotopagnosia" also considers the inability to orient and recognize the body parts of others or representations of the body (e.g., manikins, diagrams).

Typically, the cause of autotopagnosia is a lesion found in the parietal lobe of the left hemisphere of the brain. However, it as also been noted that patients with generalized brain damage present with similar symptoms of autotopagnosia.

As a concept, autotopagnosia has been criticized as nonspecific; some claim that this is a manifestation of a greater symptomatic complex of anomia, marked by an inability to name things in general—not just parts of the human body.