Because of reduced levels of trust, there can be challenges in treating PPD. However, psychotherapy, antidepressants, antipsychotics and anti-anxiety medications can play a role when an individual is receptive to intervention.

A genetic contribution to paranoid traits and a possible genetic link between this personality disorder and schizophrenia exist. A large long-term Norwegian twin study found paranoid personality disorder to be modestly heritable and to share a portion of its genetic and environmental risk factors with the other cluster A personality disorders, schizoid and schizotypal.

Psychosocial theories implicate projection of negative internal feelings and parental modeling. Cognitive theorists believe the disorder to be a result of an underlying belief that other people are unfriendly in combination with a lack in self-awareness.

Neurosis is a class of functional mental disorders involving chronic distress but neither delusions nor hallucinations. The term is no longer used by the professional psychiatric community in the United States, having been eliminated from the "Diagnostic and Statistical Manual of Mental Disorders" in 1980 with the publication of DSM III. It is still used in the .

Neurosis should not be mistaken for psychosis, which refers to a loss of touch with reality. Neither should it be mistaken for neuroticism, a fundamental personality trait proposed in the big Five personality traits theory.

STPD is rarely seen as the primary reason for treatment in a clinical setting, but it often occurs as a comorbid finding with other mental disorders. When patients with STPD are prescribed pharmaceuticals, they are most often prescribed the same drugs used to treat patients suffering from schizophrenia including traditional neuroleptics such as haloperidol and thiothixene. In order to decide which type of medication should be used, Paul Markovitz distinguishes two basic groups of schizotypal patients:

- Schizotypal patients who appear to be almost schizophrenic in their beliefs and behaviors (aberrant perceptions and cognitions) are usually treated with low doses of antipsychotic medications, e.g. thiothixene. However, it must be mentioned that long-term efficacy of neuroleptics is doubtful.

- For schizotypal patients who are more obsessive-compulsive in their beliefs and behaviors, SSRIs like Sertraline appear to be more effective.

Lamotrigine, an anti-convulsant, appears to be helpful in dealing with social isolation.

The use of antipsychotic medication is commonly the first line of treatment; however, the effectiveness after treatment is in question.

L-DOPA is effective against reduced affect display and emotional withdrawal, aloofness from society, apathy.

There are many different neuroses: obsessive–compulsive disorder, obsessive–compulsive personality disorder, impulse control disorder, anxiety disorder, hysteria, and a great variety of phobias.

According to C. George Boeree, professor emeritus at Shippensburg University, the symptoms of neurosis may involve:

Neurosis may be defined simply as a "poor ability to adapt to one's environment, an inability to change one's life patterns, and the inability to develop a richer, more complex, more satisfying personality."

Psychiatrist Kantor suggests a treatment approach using psychodynamic, supportive, cognitive, behavioral and interpersonal therapeutic methods. These methods apply to both the Passive–aggressive person and their target victim.

According to Theodore Millon, the schizotypal is one of the easiest personality disorders to identify but one of the most difficult to treat with psychotherapy. Persons with STPD usually consider themselves to be simply eccentric, productive, or nonconformist. As a rule, they underestimate maladaptiveness of their social isolation and perceptual distortions. It is not so easy to gain rapport with people who suffer from STPD due to the fact that increasing familiarity and intimacy usually increase their level of anxiety and discomfort. In most cases they do not respond to informality and humor.

Group therapy is recommended for persons with STPD only if the group is well structured and supportive. Otherwise, it could lead to loose and tangential ideation. Support is especially important for schizotypal patients with predominant paranoid symptoms, because they will have a lot of difficulties even in highly structured groups.

Pseudoneurotic schizophrenia is a postulated mental disorder categorized by the presence of two or more symptoms of mental illness such as anxiety, hysteria, and phobic or obsessive-compulsive neuroses. It is often acknowledged as a personality disorder. Patients generally display salient anxiety symptoms that disguise an underlying psychotic disorder.

In the 1940s, psychiatrists Paul Hoch and Philip Polatin created the term pseudoneurotic schizophrenia. This mental illness, however, is no longer acknowledged as a clinical entity. In 1972 it went on to be called borderline personality disorder, a term coined by Otto Friedmann Kernberg, which referred to an expansive range of issues.

Pseudoneurotic schizophrenia is in the Russian adapted version of the ICD-10 (code F21.3).

When pseudoneurotic schizophrenia was still being utilized as a diagnostic term, doctors were expected to be able to magically cure patients. Patients usually had very little understanding of themselves and the complexity of their illness. They were willing to employ any process in order to maintain mental stability. Their perception of mental stability, however, was also impaired, which made it much more difficult to make proper, helpful medication prescriptions.

Patients would often misuse medication in order to receive attention from their families. They would describe the dosage and effects of the medicine in some strange demeanor to demonstrate that their illness was physical rather than psychological. In like manner, taking medication also kept doctors concerned about the possibility of the patient developing substance dependence and/or drug addiction. Patients used this to get attention and sympathy from others.

Ideas of reference and delusions of reference describe the phenomenon of an individual's experiencing innocuous events or mere coincidences and believing they have strong personal significance. It is "the notion that everything one perceives in the world relates to one's own destiny".

In psychiatry, delusions of reference form part of the diagnostic criteria for psychotic illnesses such as schizophrenia, delusional disorder, bipolar disorder (during the elevated stages of mania), as well as schizotypal personality disorder. To a lesser extent, it can be a hallmark of paranoid personality disorder. Such symptoms can also be caused by intoxication, especially with hallucinogens or stimulants like methamphetamine.

Some debates have pervaded the field of psychology since its genesis. Perhaps one of the most salient ones deals with the nature of personality. Personality psychology studies one's distinctive style of cognition, behavior, and affect. However, this concept elicits discord among psychologists as some have insisted that it does not exist, while others struggle with issues of measurement.

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.

A self-disorder, also called ipseity disturbance, is a psychological phenomenon of disruption or diminishing of a person's sense of minimal (or basic) self. The sense of minimal self refers to the very basic sense of having experiences that are one's own; it has no properties, unlike the more extended sense of self, the narrative self, which is characterized by the person's reflections on themselves as a person, things they like, their identity, and other aspects that are the result of reflection on one's self. Disturbances in the sense of minimal self, as measured by the Examination of Anomalous Self-Experience (EASE), aggregate in the schizophrenia spectrum disorders, to include schizotypal personality disorder, and distinguish them from other conditions such as psychotic bipolar disorder and borderline personality disorder.

A monothematic delusion is a delusional state that concerns only one particular topic. This is contrasted by what is sometimes called "multi-thematic" or "polythematic" delusions where the person has a range of delusions (typically the case of schizophrenia). These disorders can occur within the context of schizophrenia or dementia or they can occur without any other signs of mental illness. When these disorders are found outside the context of mental illness, they are often caused by organic dysfunction as a result of traumatic brain injury, stroke, or neurological illness.

People who experience these delusions as a result of organic dysfunction often do not have any obvious intellectual deficiency nor do they have any other symptoms. Additionally, a few of these people even have some awareness that their beliefs are bizarre, yet they cannot be persuaded that their beliefs are false.

Treatment for perfectionism can be approached from many therapeutic directions. Some examples of psychotherapy include: cognitive-behavioral therapy (the challenging of irrational thoughts and formation of alternative ways of coping and thinking), psychoanalytic therapy (an analysis of underlying motives and issues), group therapy (where two or more clients work with one or more therapists about a specific issue, this is beneficial for those who feel as if they are the only one experiencing a certain problem), humanistic therapy (person-centered therapy where the positive aspects are highlighted), and self-therapy (personal time for the person where journaling, self-discipline, self-monitoring, and honesty with self are essential). Cognitive-behavioral therapy has been shown to successfully help perfectionists in reducing social anxiety, public self-consciousness, and perfectionism. By using this approach, a person can begin to recognize his or her irrational thinking and find an alternative way to approach situations. Cognitive-behavioral therapy is intended to help the person understand that it is okay to make mistakes sometimes and that those mistakes can become lessons learned.

Cluster B personality disorders are a categorization of personality disorders as defined in the DSM-IV and DSM-5.

Cluster B personality disorders are characterized by dramatic, overly emotional or unpredictable thinking or behavior and manipulative, exploitative interactions with others. They include antisocial personality disorder, borderline personality disorder, histrionic personality disorder and narcissistic personality disorder.

The British National Health Service has described those with this disorder as someone who, "struggles to relate to others. As a result, they show patterns of behaviour most would regard as dramatic, erratic and threatening or disturbing."

There are four recognized Cluster B personality disorders:

- Antisocial personality disorder (DSM-IV code 301.7): a pervasive disregard for the law and the rights of others.

- Borderline personality disorder (DSM-IV code 301.83): extreme "black and white" thinking, instability in relationships, self-image, identity and behavior often leading to self-harm and impulsivity.

- Histrionic personality disorder (DSM-IV code 301.50): pervasive attention-seeking behavior including inappropriately seductive behavior and shallow or exaggerated emotions.

- Narcissistic personality disorder (DSM-IV code 301.81): a pervasive pattern of grandiosity, need for admiration, and a lack of empathy.

Persons with ideas of reference may experience:

- Believing that 'somehow everyone on a passing city bus is talking about them, yet they may be able to acknowledge this is unlikely'.

- A feeling that people on television or radio are talking about or talking directly to them

- Believing that headlines or stories in newspapers are written especially for them

- Believing that events (even world events) have been deliberately contrived for them, or have special personal significance for them

- Believing that the lyrics of a song are specifically about them

- Believing that the normal function of cell phones, computers, and other electronic devices are sending secret and significant messages that only they can understand or believe.

- Seeing objects or events as being set up deliberately to convey a special or particular meaning to themselves

- Thinking 'that the slightest careless movement on the part of another person had great personal meaning...increased significance'.

- Thinking that posts on social network websites or Internet blogs have hidden meanings pertaining to them.

- Believing that the behavior of others is in reference to an abnormal, offensive body odor, which in reality is non-existent and cannot be detected by others (see: olfactory reference syndrome).

Current cognitive neuropsychology research points toward a two-factor approach to the cause of monothematic delusions. The first factor being the anomalous experience—often a neurological defect—which leads to the delusion, and the second factor being an impairment of the belief formation cognitive process.

As an example of one of these first factors, several studies point toward Capgras delusion being the result of a disorder of the affect component of face perception. As a result, while the person can recognize their spouse (or other close relation) they do not feel the typical emotional reaction, and thus the spouse does not seem like the person they once knew.

As studies have shown, these neurological defects are not enough on their own to cause delusional thinking. An additional second factor—a bias or impairment of the belief formation cognitive process—is required to solidify and maintain the delusion. Since we do not currently have a solid cognitive model of the belief formation process, this second factor is still somewhat of an unknown.

Some research has shown that delusional people are more prone to jumping to conclusions, and thus they would be more likely to take their anomalous experience as veridical and make snap judgments based on these experiences. Additionally, studies have shown that they are more prone to making errors due to matching bias—indicative of a tendency to try and confirm the rule. These two judgment biases help explain how delusion-prone people could grasp onto extreme delusions and be very resistant to change.

Researchers claim this is enough to explain the delusional thinking. However, other researchers still argue that these biases are not enough to explain why they remain completely impervious to evidence over time. They believe that there must be some additional unknown neurological defect in the patient's belief system (probably in the right hemisphere).

Many people with sexual obsessions are alarmed that they seem to lose their sex drive. People with OCD may see this as evidence that they no longer have normal sexual attractions and are in fact deviant in some way. Some may wonder if medication is the answer to the problem. Medication is a double-edged sword. Drugs specifically for erectile dysfunction (i.e. Viagra, Cialis) are not the answer for people with untreated OCD. The sexual organs are working properly, but it is the anxiety disorder that interferes with normal libido.

Medications specifically for OCD (typically SSRI medications) will help alleviate the anxiety but will also cause some sexual dysfunction in about a third of patients. For many the relief from the anxiety is enough to overcome the sexual problems caused by the medication. For others, the medication itself makes sex truly impossible. This may be a temporary problem, but if it persists a competent psychiatrist can often adjust the medications to overcome this side-effect.

The Diagnostic and Statistical Manual of Mental Disorders revision IV (DSM-IV) describes passive–aggressive personality disorder as a "pervasive pattern of negativistic attitudes and passive resistance to demands for adequate performance in social and occupational situations."

Passive-aggressive behavior is the obligatory symptom of the passive–aggressive personality disorder. Persons with passive–aggressive personality disorder are characterized by procrastination, covert obstructionism, inefficiency and stubbornness.

People with sexual obsessions can devote an excessive amount of time and energy attempting to understand the obsessions. They usually decide they are having these problems because they are defective in some way, and they are often too ashamed to seek help. Because sexual obsessions are not as well-described in the research literature, many therapists may fail to properly diagnose OCD in a client with primary sexual obsessions. Mental health professionals unfamiliar with OCD may even attribute the symptoms to an unconscious wish (typically in the case of psychoanalysts or psychodynamic therapists), sexual identity crisis, or hidden paraphilia. Such a misdiagnosis only panics an already distressed individual. Fortunately, sexual obsessions respond to the same type of effective treatments available for other forms of OCD: cognitive-behavioral therapy and serotonergic antidepressant medications (SSRIs). People with sexual obsessions may, however, need a longer and more aggressive course of treatment.

The minimal self has been likened to a "flame that enlightens its surroundings and thereby itself." Unlike the extended self, which is composed of properties such as the person's identity, the person's narrative, and other aspects that can be gleaned from reflection, the minimal self has no properties, but refers to the "mine-ness" "given-ness" of experience, that the experiences are that of the person having them in that person's stream of consciousness. These experiences that are part of the minimal self are normally "tacit" and implied, requiring no reflection on the part of the person experiencing to know that the experience is theirs. The minimal self cannot be further elaborated and normally one cannot grasp it upon reflection. The minimal self goes hand-in-hand with immersion in the shared social world, such that "[t]he world is always pregiven, ie, tacitly grasped as a self-evident background of all experiencing and meaning." This is the self-world structure.

De Warren gives an example of the minimal self combined with immersion in the shared social world: "When looking at this tree in my backyard, my consciousness is directed toward the tree and not toward my own act of perception. I am, however, aware of myself as perceiving this tree, yet this self-awareness (or self-consciousness) is not itself thematic." The focus is normally on the tree itself, not on the person's own act of seeing the tree: to know that one is seeing the tree does not require an act of reflection.

Thought insertion is defined by the ICD-10 as feeling as if one's thoughts are not one's own, but rather belong to someone else and have been inserted into one's mind. The person experiencing thought insertion will not necessarily know where the thought is coming from, but is able to distinguish between their own thoughts and those inserted into their minds. However, patients do not experience all thoughts as inserted, only certain ones, normally following a similar content or pattern. This phenomenon is classified as a delusion. A person with this delusional belief is convinced of the veracity of their beliefs and is unwilling to accept such diagnosis.

Thought insertion is a common symptom of psychosis and occurs in many mental disorders and other medical conditions. However, thought insertion is most commonly associated with schizophrenia. Thought insertion, along with thought broadcasting, thought withdrawal, thought blocking and other first rank symptoms, is a primary symptom and should not be confused with the delusional explanation given by the respondent. Although normally associated with some form of psychopathology, thought insertion can also be experienced in those considered nonpathological, usually in spiritual contexts, but also in culturally influenced practices such as mediumship and automatic writing.

Examples of thought insertion:

"She said that sometimes it seemed to be her own thought 'but I don't get the feeling that it is'. She said her 'own thoughts might say the same thing', 'but the feeling isn't the same', 'the feeling is that it is somebody else's'"

"I look out the window and I think that the garden looks nice and the grass looks cool, but the thoughts of Eamonn Andrews come into my mind. There are no other thoughts there, only his. He treats my mind like a screen and flashes thoughts onto it like you flash a picture"

"The subject has thoughts that she thinks are the thoughts of other people, somehow occurring in her own mind. It is not that the subject thinks that other people are making her think certain thoughts as if by hypnosis or psychokinesis, but that other people think the thoughts using the subject's mind as a psychological medium."

Most of the treatments for thought insertion are not specific to the symptom, but rather the symptom is treated through treatment of the psychopathology that causes it. However, one case report considers a way to manage thought insertion through performing thoughts as motor actions of speech. In other words, the patient would speak his thoughts out loud in order to re-give himself the feeling of agency as he could hear himself speaking and then contributing the thought to himself.