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.

Narcissistic personality disorder is rarely the primary reason for people seeking mental health treatment. When people with NPD enter treatment, it is typically prompted by life difficulties or to seek relief from another disorder, such as major depressive disorder, substance use disorders, bipolar disorder, or eating disorders, or at the insistence of relatives and friends. This is partly because individuals with NPD generally have poor insight and fail to recognize their perception and behavior as inappropriate and problematic due to their very positive self-image.

Treatment for NPD is centered around psychotherapy. In the 1960s, Heinz Kohut and Otto Kernberg challenged the conventional wisdom of the time by outlining clinical strategies for using psychoanalytic psychotherapy with clients with NPD that they claimed were effective in treating the disorder. Contemporary treatment modalities commonly involve transference-focused, metacognitive, and schema-focused therapies. Some improvement might be observed through the treatment of symptoms related to comorbid disorders with psychopharmaceuticals, but , according to Elsa Ronningstam, psychologist at Harvard Medical School, "Alliance building and engaging the patient's sense of agency and reflective ability are essential for change in pathological narcissism."

Pattern change strategies performed over a long period of time are used to increase the ability of those with NPD to become more empathic in everyday relationships. To help modify their sense of entitlement and self-centeredness schema, the strategy is to help them identify how to utilize their unique talents and to help others for reasons other than their own personal gain. This is not so much to change their self-perception of their "entitlement" feeling but more to help them empathize with others. Another type of treatment would be temperament change. Psychoanalytic psychotherapy may be effective in treating NPD, but therapists must recognize the patient's traits and use caution in tearing down narcissistic defenses too quickly. Anger, rage, impulsivity, and impatience can be worked on with skill training. Therapy may not be effective because patients may receive feedback poorly and defensively. Anxiety disorders and somatoform dysfunctions are prevalent but the most common would be depression.

Group treatment has its benefits as the effectiveness of receiving peer feedback rather than the clinician's may be more accepted, but group therapy can also contradict itself as the patient may show "demandingness, egocentrism, social isolation and withdrawal, and socially deviant behavior". Researchers originally thought group therapy among patients with NPD would fail because it was believed that group therapy required empathy that NPD patients lack. However, studies show group therapy does hold value for patients with NPD because it lets them explore boundaries, develop trust, increase self-awareness, and accept feedback. Relationship therapy stresses the importance of learning and applying four basic interpersonal skills: "...effective expression, empathy, discussion and problem solving/conflict resolution". Marital/relationship therapy is most beneficial when both partners participate.

No medications are indicated for treating NPD, but may be used to treat co-occurring mental conditions or symptoms that may be associated with it such as depression, anxiety, and impulsiveness if present.

Paranoia is an instinct or thought process believed to be heavily influenced by anxiety or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory, or beliefs of concerning a perceived threat towards oneself (e.g. ""Everyone is out to get me"", which is an American parochial phrase). Paranoia is distinct from phobias, which also involve irrational fear, but usually no blame. Making false accusations and the general distrust of others also frequently accompany paranoia. For example, an incident most people would view as an accident or coincidence, a paranoid person might believe was intentional. Paranoia is a central symptom of psychosis. It is also a matter of personal tolerance for the individual that might be in conflict with psychiatric diagnoses.

Social circumstances appear to be highly influential on paranoid beliefs. Based on data collected by means of a mental health survey distributed to residents of Ciudad Juárez, Chihuahua (in Mexico) and El Paso, Texas (in the United States), paranoid beliefs seem to be associated with feelings of powerlessness and victimization, enhanced by social situations. Potential causes of these effects included a sense of believing in external control, and mistrust which can be strengthened by lower socioeconomic status. Those living in a lower socioeconomic status may feel less in control of their own lives. In addition, this study explains that females have the tendency to believe in external control at a higher rate than males, potentially making females more susceptible to mistrust and the effects of socioeconomic status on paranoia.

Emanuel Messinger reports that surveys have revealed that those exhibiting paranoia can evolve from parental relationships and dis-trustworthy environments. These environments could include being very disciplinary, stringent, and unstable. It was even noted that, "indulging and pampering (thereby impressing the child that he is something special and warrants special privileges)," can be contributing backgrounds. Experiences likely to enhance or manifest the symptoms of paranoia include increased rates of disappointment, stress, and a hopeless state of mind.

Discrimination has also been reported as a potential predictor of paranoid delusions. Such reports that paranoia seemed to appear more in older patients who had experienced higher levels of discrimination throughout their lives. In addition to this it has been noted that immigrants are quite susceptible to forms of psychosis. This could be due to the aforementioned effects of discriminatory events and humiliation.

Grandiosity refers to an unrealistic sense of superiority—a sustained view of oneself as better than others that causes the narcissist to view others with disdain or as inferior—as well as to a sense of uniqueness: the belief that few others have anything in common with oneself and that one can only be understood by a few or very special people. It also occurs in reactive attachment disorder.

Grandiosity is chiefly associated with narcissistic personality disorder, but also commonly features in manic or hypomanic episodes of bipolar disorder.

The effectiveness of psychotherapeutic and pharmacological interventions in the treatment of narcissistic personality disorder has yet to be systematically and empirically investigated. Clinical practice guidelines for the disorder have not yet been created, and current treatment recommendations are largely based on theoretical psychodynamic models of NPD and the experiences of clinicians with afflicted individuals in clinical settings.

The presence of NPD in patients undergoing psychotherapy for the treatment of other mental disorders is associated with slower treatment progress and higher dropout rates.

Currently, genetic research for the understanding of the development of personality disorders is severely lacking. However, there are a few possible risk factors currently in discovery. Researchers are currently looking into genetic mechanisms for traits such as aggression, fear and anxiety, which are associated with diagnosed individuals. More research is being conducted into disorder specific mechanisms.

According to Professor Emily Simonoff of the Institute of Psychiatry, Psychology and Neuroscience, "childhood hyperactivity and conduct disorder showed equally strong prediction of antisocial personality disorder (ASPD) and criminality in early and mid-adult life. Lower IQ and reading problems were most prominent in their relationships with childhood and adolescent antisocial behaviour."

There are many different forms (modalities) of treatment used for personality disorders:

- Individual psychotherapy has been a mainstay of treatment. There are long-term and short-term (brief) forms.

- Family therapy, including couples therapy.

- Group therapy for personality dysfunction is probably the second most used.

- Psychological-education may be used as an addition.

- Self-help groups may provide resources for personality disorders.

- Psychiatric medications for treating symptoms of personality dysfunction or co-occurring conditions.

- Milieu therapy, a kind of group-based residential approach, has a history of use in treating personality disorders, including therapeutic communities.

- The practice of mindfulness that includes developing the ability to be nonjudgmentally aware of unpleasant emotions appears to be a promising clinical tool for managing different types of personality disorders.

There are different specific theories or schools of therapy within many of these modalities. They may, for example, emphasize psychodynamic techniques, or cognitive or behavioral techniques. In clinical practice, many therapists use an 'eclectic' approach, taking elements of different schools as and when they seem to fit to an individual client. There is also often a focus on common themes that seem to be beneficial regardless of techniques, including attributes of the therapist (e.g. trustworthiness, competence, caring), processes afforded to the client (e.g. ability to express and confide difficulties and emotions), and the match between the two (e.g. aiming for mutual respect, trust and boundaries).

ASPD is considered to be among the most difficult personality disorders to treat. Because of their very low or absent capacity for remorse, individuals with ASPD often lack sufficient motivation and fail to see the costs associated with antisocial acts. They may only simulate remorse rather than truly commit to change: they can be seductively charming and dishonest, and may manipulate staff and fellow patients during treatment. Studies have shown that outpatient therapy is not likely to be successful, but the extent to which persons with ASPD are entirely unresponsive to treatment may have been exaggerated.

Those with ASPD may stay in treatment only as required by an external source, such as parole conditions. Residential programs that provide a carefully controlled environment of structure and supervision along with peer confrontation have been recommended. There has been some research on the treatment of ASPD that indicated positive results for therapeutic interventions.

Psychotherapy also known as talk therapy is found to help treat patients with ASPD.Schema therapy is also being investigated as a treatment for ASPD. A review by Charles M. Borduin features the strong influence of Multisystemic therapy (MST) that could potentially improve this imperative issue. However, this treatment requires complete cooperation and participation of all family members. Some studies have found that the presence of ASPD does not significantly interfere with treatment for other disorders, such as substance abuse, although others have reported contradictory findings.

Therapists working with individuals with ASPD may have considerable negative feelings toward patients with extensive histories of aggressive, exploitative, and abusive behaviors. Rather than attempt to develop a sense of conscience in these individuals, which is extremely difficult considering the nature of the disorder, therapeutic techniques are focused on rational and utilitarian arguments against repeating past mistakes. These approaches would focus on the tangible, material value of prosocial behavior and abstaining from antisocial behavior. However, the impulsive and aggressive nature of those with this disorder may limit the effectiveness of even this form of therapy.

The use of medications in treating antisocial personality disorder is still poorly explored, and no medications have been approved by the FDA to specifically treat ASPD. A 2010 Cochrane review of studies that explored the use of pharmaceuticals in ASPD patients, of which 8 studies met the selection criteria for review, concluded that the current body of evidence was inconclusive for recommendations concerning the use of pharmaceuticals in treating the various issues of ASPD. Nonetheless psychiatric medications such as antipsychotics, antidepressants, and mood stabilizers can be used to control symptoms such as aggression and impulsivity, as well as treat disorders that may co-occur with ASPD for which medications are indicated.

According to the Mayo Clinic, it is best to start receiving treatment for paranoid schizophrenia as early as possible and to maintain the treatment throughout life. Continuing treatment will help keep the serious symptoms under control and allow the person to lead a more fulfilling life. This illness is typically unpreventable.

It has a strong hereditary component with a first degree parent or sibling. There is some possibility that there are environmental influences including "prenatal exposure to a viral infection, low oxygen levels during birth (from prolonged labor or premature birth), exposure to a virus during infancy, early parental loss or separation, and verbal, physical or sexual abuse in childhood". Eliminating any of these factors could help reduce an individual's future risk of developing paranoid schizophrenia.

Research suggests that the severity of the delusions of grandeur is directly related to a higher self-esteem in individuals and inversely related to any individual’s severity of depression and negative self-evaluations. Lucas "et al." found that there is no significant gender difference in the establishment of grandiose delusion. However, there is a claim that ‘the particular component of Grandiose delusion’ may be variable across both genders. Also, it had been noted that the presence of GDs in people with at least grammar or high school education was greater than lesser educated persons. Similarly, the presence of grandiose delusions in individuals who are the eldest is greater than in individuals who are the youngest of their siblings.

Grandiose delusions (GD), delusions of grandeur, expansive delusions also known as megalomania are a subtype of delusion that occur in patients suffering from a wide range of psychiatric diseases, including two-thirds of patients in manic state of bipolar disorder, half of those with schizophrenia, patients with the grandiose subtype of delusional disorder, and a substantial portion of those with substance abuse disorders. GDs are characterized by fantastical beliefs that one is famous, omnipotent, wealthy, or otherwise very powerful. The delusions are generally fantastic and typically have a religious, science fictional, or supernatural theme. There is a relative lack of research into GD, in contrast to persecutory delusions and auditory hallucinations. About 10% of healthy people experience grandiose thoughts but do not meet full criteria for a diagnosis of GD.

Paranoid schizophrenia is an illness that typically requires lifelong treatment with neuroleptics to allow someone to have a relatively stable and normal lifestyle. In order to be successfully treated, a person with schizophrenia should seek help from family or primary care doctors, psychiatrists, psychotherapists, pharmacists, family members, case workers, psychiatric nurses, or social workers, provided he or she is not unable to do so, due to many people with schizophrenia having the inability to accept their condition. Non-compliance with neuroleptics may also occur if the patient considers the side effects (such as extrapyramidal symptoms) to be more debilitating than the condition itself. The main options that are offered for the treatment of paranoid schizophrenia are the following: neuroleptics, psychotherapy, hospitalization, electroconvulsive therapy, and vocational skills training.

There are many different types of disorders that have similar symptoms to paranoid schizophrenia. There are tests that psychiatrists perform to achieve a correct diagnosis. They include "psychiatric evaluation, in which the doctor or psychiatrist will ask a series of questions about the patient's symptoms, psychiatric history, and family history of mental health problems; medical history and exam, in which the doctor will ask about one's personal and family health history and will also perform a complete physical examination to check for medical issues that could be causing or contributing to the problem; laboratory tests in which the doctor will order simple blood and urine tests can rule out other medical causes of symptoms".

There are side effects associated with antipsychotic medication. Neuroleptics can cause high blood pressure and high cholesterol. Many people who take them exhibit weight gain and have a higher risk of developing diabetes.

Malignant narcissism is a psychological syndrome comprising an extreme mix of narcissism, antisocial behavior, aggression, and sadism. Often grandiose, and always ready to raise hostility levels, the malignant narcissist undermines organizations in which they are involved, and dehumanizes the people with whom they associate.

Malignant narcissism is a hypothetical, experimental diagnostic category. Narcissistic personality disorder is found in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-IV-TR), while malignant narcissism is not. As a hypothetical syndrome, malignant narcissism could include aspects of narcissistic personality disorder as well as paranoia. The importance of malignant narcissism and of projection as a defense mechanism has been confirmed in paranoia, as well as "the patient's vulnerability to malignant narcissistic regression".

The evidence for the effectiveness of early interventions to prevent psychosis appeared inconclusive. Whilst early intervention in those with a psychotic episode might improve short term outcomes, little benefit was seen from these measures after five years. However, there is evidence that cognitive behavioral therapy (CBT) may reduce the risk of becoming psychotic in those at high risk, and in 2014 the UK National Institute for Health and Care Excellence (NICE) recommended preventive CBT for people at risk of psychosis.

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.

The treatment of psychosis depends on the specific diagnosis (such as schizophrenia, bipolar disorder or substance intoxication). The first-line psychiatric treatment for many psychotic disorders is antipsychotic medication, which can reduce the positive symptoms of psychosis in about 7 to 14 days.

The choice of which antipsychotic to use is based on benefits, risks, and costs. It is debatable whether, as a class, typical or atypical antipsychotics are better. Tentative evidence supports that amisulpride, olanzapine, risperidone and clozapine may be more effective for positive symptoms but result in more side effects. Typical antipsychotics have equal drop-out and symptom relapse rates to atypicals when used at low to moderate dosages. There is a good response in 40–50%, a partial response in 30–40%, and treatment resistance (failure of symptoms to respond satisfactorily after six weeks to two or three different antipsychotics) in 20% of people. Clozapine is an effective treatment for those who respond poorly to other drugs ("treatment-resistant" or "refractory" schizophrenia), but it has the potentially serious side effect of agranulocytosis (lowered white blood cell count) in less than 4% of people.

Most people on antipsychotics get side effects. People on typical antipsychotics tend to have a higher rate of extrapyramidal side effects while some atypicals are associated with considerable weight gain, diabetes and risk of metabolic syndrome; this is most pronounced with olanzapine, while risperidone and quetiapine are also associated with weight gain. Risperidone has a similar rate of extrapyramidal symptoms to haloperidol.

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.

Few medications are approved specifically for schizoaffective disorder. In general, medications are chosen to reduce symptoms of psychosis and mood disorder.

Antipsychotic medication is usually required both for acute treatment and the prevention of relapse. There is no single antipsychotic of choice in treating schizoaffective disorder, but atypical antipsychotics should be considered because they have mood-stabilizing activity. Paliperidone is an antipsychotic with FDA approval for the treatment of schizoaffective disorder. Antipsychotics should be used at the minimum dose necessary to control symptoms. Potential side effects include extrapyramidal symptoms, including tremor, muscle stiffness, and restlessness or akathisia. Atypical antipsychotics carry a risk of metabolic syndrome, including weight gain, increased blood sugar, and increased blood cholesterol, so regular monitoring of weight and bloodwork should be carried out. Some atypical antipsychotics, such as ziprasidone and aripiprazole, are associated with less risk than others, such as olanzapine. Medication choice is based on how effectively it reduces symptoms, how few side effects it causes, and cost.

In people with treatment-refractory psychosis, a clozapine trial should be considered. Clozapine is an atypical antipsychotic that is recognized as being particularly effective when other antipsychotic agents have failed. Clozapine should also be considered in people with chronic and persistent suicidal thinking and behaviour, as it has been shown to reduce the risk of suicide in patients with schizoaffective disorder and a history of suicidality. Between 0.5 and 2% of patients taking clozapine may develop a life-threatening complication called agranulocytosis, which is a significant drop in a type of white blood cell. Because of this risk, people taking clozapine must have regular monitoring of blood cell counts.

The management of the bipolar type of schizoaffective disorder is similar to the treatment of bipolar disorder, with the goal of preventing mood episodes and cycling. Lithium or anticonvulsant mood stabilizers such as valproic acid, carbamazepine, and lamotrigine are prescribed in combination with an antipsychotic.

For depression, if an antidepressant is prescribed, "extra attentiveness must be given" by the prescribing clinician due its risk for long-term mood cycle acceleration (that is, inducing more frequent episodes of depression per unit of time) and medication-induced psychosis or mania. For individuals who show emerging psychosis, mania, mixed episode symptoms, or mood cycle acceleration, switching to an antipsychotic plus lithium or lamotrigine is preferable to antidepressants.

For individuals who experience anxiety, anti-anxiety medications can be used, usually on a short-term basis. Benzodiazepines, including lorazepam, clonazepam and diazepam, are types of anti-anxiety medications. Care must be taken when prescribing benzodiazepines due to the risk of the patient developing tolerance and dependence.

Before beginning treatment for mania, careful differential diagnosis must be performed to rule out secondary causes.

The acute treatment of a manic episode of bipolar disorder involves the utilization of either a mood stabilizer (valproate, lithium, or carbamazepine) or an atypical antipsychotic (olanzapine, quetiapine, risperidone, or aripiprazole). Although hypomanic episodes may respond to a mood stabilizer alone, full-blown episodes are treated with an atypical antipsychotic (often in conjunction with a mood stabilizer, as these tend to produce the most rapid improvement).

When the manic behaviours have gone, long-term treatment then focuses on prophylactic treatment to try to stabilize the patient's mood, typically through a combination of pharmacotherapy and psychotherapy. The likelihood of having a relapse is very high for those who have experienced two or more episodes of mania or depression. While medication for bipolar disorder is important to manage symptoms of mania and depression, studies show relying on medications alone is not the most effective method of treatment. Medication is most effective when used in combination with other bipolar disorder treatments, including psychotherapy, self-help coping strategies, and healthy lifestyle choices.

Lithium is the classic mood stabilizer to prevent further manic and depressive episodes. A systematic review found that long term lithium treatment substantially reduces the risk of bipolar manic relapse, by 42%. Anticonvulsants such as valproate, oxcarbazepine and carbamazepine are also used for prophylaxis. More recent drug solutions include lamotrigine, which is another anticonvulsant. Clonazepam (Klonopin) is also used. Sometimes atypical antipsychotics are used in combination with the previous mentioned medications as well, including olanzapine (Zyprexa) which helps treat hallucinations or delusions, Asenapine (Saphris, Sycrest), aripiprazole (Abilify), risperidone, ziprasidone, and clozapine which is often used for people who do not respond to lithium or anticonvulsants.

Verapamil, a calcium-channel blocker, is useful in the treatment of hypomania and in those cases where lithium and mood stabilizers are contraindicated or ineffective. Verapamil is effective for both short-term and long-term treatment.

Antidepressant monotherapy is not recommended for the treatment of depression in patients with bipolar disorders I or II, and no benefit has been demonstrated by combining antidepressants with mood stabilizers in these patients.

Electroconvulsive therapy, or ECT, may be considered for patients with schizoaffective disorder experiencing severe depression or severe psychotic symptoms that have not responded to treatment with antipsychotics.

Treatment consists of supportive care during the acute intoxication phase: maintaining hydration, body temperature, blood pressure, and heart rate at acceptable levels until the drug is sufficiently metabolized to allow vital signs to return to baseline. Typical and atypical antipsychotics have been shown to be helpful in the early stages of treatment. This is followed by abstinence from psychostimulants supported with counseling or medication designed to assist the individual preventing a relapse and the resumption of a psychotic state.

Often in those who have experienced their first episode of hypomania – generally without psychotic features – there may be a long or recent history of depression or a mix of hypomania combined with depression (known as mixed-state) prior to the emergence of manic symptoms. This commonly surfaces in the mid to late teens. Because the teenage years are typically an emotionally charged time of life, it is not unusual for mood swings to be passed off as normal hormonal teen behavior and for a diagnosis of bipolar disorder to be missed until there is evidence of an obvious manic or hypomanic phase.

Hypomania may also occur as a side effect of pharmaceuticals prescribed for conditions or diseases other than psychological states or mood disorders. In those instances, as in cases of drug-induced hypomanic episodes in unipolar depressives, the hypomania can almost invariably be eliminated by lowering medication dosage, withdrawing the drug entirely, or changing to a different medication if discontinuation of treatment is not possible.

Hypomania may also be triggered by the occurrence of a highly exciting event in the patient's situation, such as a substantial financial gain or recognition.

Hypomania can be associated with narcissistic personality disorder.