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.

PPD occurs in about 0.5%–2.5% of the general population. It is seen in 2%–10% of psychiatric outpatients. It is more common in males.

This diagnostic rubric is not recommended for general use because it is not clearly demarcated either from simple schizophrenia or from schizoid or paranoid personality disorders, or possibly autism and Asperger syndrome as currently diagnosed. If the term is used, three or four of the typical features listed above should have been present, continuously or episodically, for at least 2 years. The individual must never have met criteria for schizophrenia itself. A history of schizophrenia in a first-degree relative gives additional weight to the diagnosis but is not a prerequisite.

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.

The diagnosis of pseudoneurotic schizophrenia can only be made with clinical observation by a mental health professional and by the patient's explanation of his or her experiences. A patient must identify with at least two of these symptoms in order to be distinguished as a pseudoneurotic schizophrenic. The intensity of a symptom may vary with the individual patient's severity of the disorder. The symptoms are organized into disorders of thinking and association, disorders of emotional regulation, disorders of sensorimotor and autonomic functioning, pan-anxiety, pan-neurosis, and pansexuality. The two symptoms can fall under any of these categories.

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).

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.

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."

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.

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.

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.

These are the current criteria:

The ICD is currently in revision and ICD-11 is expected to come out in 2018. In the preliminary Beta Draft version, there is no longer a diagnostic category of simple schizophrenia and all subtypes have been eliminated.

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.

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.

For a child or adolescent to qualify for a diagnosis of ODD, behaviours must cause considerable distress for the family or interfere significantly with academic or social functioning. Interference might take the form of preventing the child or adolescent from learning at school or making friends, or placing him or her in harmful situations. These behaviours must also persist for at least six months. Effects of ODD can be greatly amplified by other disorders in comorbidity such as ADHD. Other common comorbid disorders include depression and substance use disorders.

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.

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.

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).

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.

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).

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."

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.

To date, cognitive behavioral therapy (CBT) is the best established treatment for a variety of somatoform disorders including somatization disorder. CBT aims to help patients realize their ailments are not catastrophic and to enable them to gradually return to activities they previously engaged in, without fear of "worsening their symptoms". Consultation and collaboration with the primary care physician also demonstrated some effectiveness. The use of antidepressants is preliminary but does not yet show conclusive evidence. Electroconvulsive shock therapy (ECT) has been used in treating somatization disorder among the elderly; however, the results were still debatable with some concerns around the side effects of using ECT. Overall, psychologists recommend addressing a common difficulty in patients with somatization disorder in the reading of their own emotions. This may be a central feature of treatment; as well as developing a close collaboration between the GP, the patient and the mental health practitioner.