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.

There is a significant difference between the number of those who would benefit from treatment and the number of those who are treated. The so-called "treatment gap" is a function of the disinclination of the afflicted to submit for treatment, an underdiagnosing of the disorder by healthcare providers, and the limited availability and access to state-of-the-art treatments. Nonetheless, individuals with BPD accounted for about 20 percent of psychiatric hospitalizations in one survey. The majority of individuals with BPD who are in treatment continue to use outpatient treatment in a sustained manner for several years, but the number using the more restrictive and costly forms of treatment, such as inpatient admission, declines with time.

Experience of services varies. Assessing suicide risk can be a challenge for clinicians, and patients themselves tend to underestimate the lethality of self-injurious behaviors. People with BPD typically have a chronically elevated risk of suicide much above that of the general population and a history of multiple attempts when in crisis. Approximately half the individuals who commit suicide meet criteria for a personality disorder. Borderline personality disorder remains the most commonly associated personality disorder with suicide.

After the death of a patient in 2014 NHS England was criticised by a coroner for the lack of commissioned services to support such patients. Evidence was given that 45% of mentally disordered females had BPD and there was no provision or priority for therapeutic psychological services. There were only 60 specialised inpatient beds in England – all in the North East or London.

A 2010 review by the Cochrane collaboration found that no medications show promise for "the core BPD symptoms of chronic feelings of emptiness, identity disturbance and abandonment". However, the authors found that some medications may impact isolated symptoms associated with BPD or the symptoms of comorbid conditions. A 2017 review examined evidence published since the 2010 Cochrane review and found that "evidence of effectiveness of medication for BPD remains very mixed and is still highly compromised by suboptimal study design".

Of the typical antipsychotics studied in relation to BPD, haloperidol may reduce anger and flupenthixol may reduce the likelihood of suicidal behavior. Among the atypical antipsychotics, one trial found that aripiprazole may reduce interpersonal problems and impulsivity. Olanzapine may decrease affective instability, anger, psychotic paranoid symptoms, and anxiety, but a placebo had a greater ameliorative impact on suicidal ideation than olanzapine did. The effect of ziprasidone was not significant.

Of the mood stabilizers studied, valproate semisodium may ameliorate depression, interpersonal problems, and anger. Lamotrigine may reduce impulsivity and anger; topiramate may ameliorate interpersonal problems, impulsivity, anxiety, anger, and general psychiatric pathology. The effect of carbamazepine was not significant. Of the antidepressants, amitriptyline may reduce depression, but mianserin, fluoxetine, fluvoxamine, and phenelzine sulfate showed no effect. Omega-3 fatty acid may ameliorate suicidality and improve depression. As of 2017, trials with these medications had not been replicated and the effect of long-term use had not been assessed.

Because of weak evidence and the potential for serious side effects from some of these medications, the UK National Institute for Health and Clinical Excellence (NICE) 2009 clinical guideline for the treatment and management of BPD recommends, "Drug treatment should not be used specifically for borderline personality disorder or for the individual symptoms or behavior associated with the disorder." However, "drug treatment may be considered in the overall treatment of comorbid conditions". They suggest a "review of the treatment of people with borderline personality disorder who do not have a diagnosed comorbid mental or physical illness and who are currently being prescribed drugs, with the aim of reducing and stopping unnecessary drug treatment".

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.

No medications are indicated for directly treating schizoid personality disorder, but certain medications may reduce the symptoms of SPD as well as treat co-occurring mental disorders. The symptoms of SPD mirror the negative symptoms of schizophrenia, such as anhedonia, blunted affect and low energy, and SPD is thought to be part of the "schizophrenic spectrum" of disorders, which also includes the schizotypal and paranoid personality disorders, and may benefit from the medications indicated for schizophrenia. Originally, low doses of atypical antipsychotics like risperidone or olanzapine were used to alleviate social deficits and blunted affect. However, a recent review concluded that atypical antipsychotics were ineffective for treating personality disorders. In contrast, the substituted amphetamine Bupropion may be used to treat anhedonia. Likewise, Modafinil may be effective in treating some of the negative symptoms of schizophrenia, which are reflected in the symptomatology of SPD and therefore may help as well. Lamotrigine, SSRIs, TCAs, MAOIs and Hydroxyzine may help counter social anxiety in people with SPD if present, though social anxiety may not be a main concern for the people who have SPD. However, it is not general practice to treat SPD with medications, other than for the short term treatment of acute co-occurring Axis I conditions (e.g. depression).

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.

People with schizoid personality disorder rarely seek treatment for their condition. This is an issue found in many personality disorders, which prevents many people who are afflicted with these conditions from coming forward for treatment: They tend to view their condition as not conflicting with their self-image and their abnormal perceptions and behaviors as rational and appropriate. There is little data on the effectiveness of various treatments on this personality disorder because it is seldom seen in clinical settings. However, those in treatment have the option of medication and therapy.

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.

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.

Treatment is often prompted by depression associated with dissolved romantic relationships. Medication does little to affect the personality disorder, but may be helpful with symptoms such as depression. Treatment for HPD itself involves psychotherapy, including cognitive therapy.

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.

Another example of treatment besides coding is Functional Ideographic Assessment Template. The functional ideographic assessment template, also known as FIAT, was used as a way to generalize the clinical processes of functional analytic psychotherapy. The template was made by a combined effort of therapists and can be used to represent the behaviors that are a focus for this treatment. Using the FIAT therapists can create a common language to get stable and accurate communication results through functional analytic psychotherapy at the ease of the client; as well as the therapist.

There is a general lack of consensus in the diagnosis and treatment of DID and research on treatment effectiveness focuses mainly on clinical approaches described in case studies. General treatment guidelines exist that suggest a phased, eclectic approach with more concrete guidance and agreement on early stages but no systematic, empirically-supported approach exists and later stages of treatment are not well described and have no consensus. Even highly experienced therapists have few patients that achieve a unified identity. Common treatment methods include an eclectic mix of psychotherapy techniques, including cognitive behavioral therapy (CBT), insight-oriented therapies, dialectical behavioral therapy (DBT), hypnotherapy and eye movement desensitization and reprocessing (EMDR). Medications can be used for comorbid disorders or targeted symptom relief. Some behavior therapists initially use behavioral treatments such as only responding to a single identity, and then use more traditional therapy once a consistent response is established. Brief treatment due to managed care may be difficult, as individuals diagnosed with DID may have unusual difficulties in trusting a therapist and take a prolonged period to form a comfortable therapeutic alliance. Regular contact (weekly or biweekly) is more common, and treatment generally lasts years—not weeks or months. Sleep hygiene has been suggested as a treatment option, but has not been tested. In general there are very few clinical trials on the treatment of DID, none of which were randomized controlled trials.

Therapy for DID is generally phase oriented. Different alters may appear based on their greater ability to deal with specific situational stresses or threats. While some patients may initially present with a large number of alters, this number may reduce during treatment—though it is considered important for the therapist to become familiar with at least the more prominent personality states as the "host" personality may not be the "true" identity of the patient. Specific alters may react negatively to therapy, fearing the therapist's goal is to eliminate the alter (particularly those associated with illegal or violent activities). A more realistic and appropriate goal of treatment is to integrate adaptive responses to abuse, injury or other threats into the overall personality structure. There is debate over issues such as whether exposure therapy (reliving traumatic memories, also known as abreaction), engagement with alters and physical contact during therapy are appropriate and there are clinical opinions both for and against each option with little high-quality evidence for any position.

Brandt et al., noting the lack of empirical studies of treatment effectiveness, conducted a survey of 36 clinicians expert in treating dissociative disorder (DD) who recommended a three-stage treatment. They agreed that skill building in the first stage is important so the patient can learn to handle high risk, potentially dangerous behavior, as well as emotional regulation, interpersonal effectiveness and other practical behaviors. In addition, they recommended "trauma-based cognitive therapy" to reduce cognitive distortions related to trauma; they also recommended that the therapist deal with the dissociated identities early in treatment. In the middle stage, they recommended graded exposure techniques, along with appropriate interventions as needed. The treatment in the last stage was more individualized; few with DD became integrated into one identity.

The International Society for the Study of Trauma and Dissociation has published guidelines to phase-oriented treatment in adults as well as children and adolescents that are widely used in the field of DID treatment. The first phase of therapy focuses on symptoms and relieving the distressing aspects of the condition, ensuring the safety of the individual, improving the patient's capacity to form and maintain healthy relationships, and improving general daily life functioning. Comorbid disorders such as substance abuse and eating disorders are addressed in this phase of treatment. The second phase focuses on stepwise exposure to traumatic memories and prevention of re-dissociation. The final phase focuses on reconnecting the identities of disparate alters into a single functioning identity with all its memories and experiences intact.

A study was conducted with the goal of developing an "expertise-based prognostic model for the treatment of complex posttraumatic stress disorder (PTSD) and dissociative identity disorder (DID)". Researchers constructed a two-stage survey and factor analyses performed on the survey elements found 51 factors common to complex PTSD and DID. The authors concluded from their findings: "The model is supportive of the current phase-oriented treatment model, emphasizing the strengthening of the therapeutic relationship and the patient's resources in the initial stabilization phase. Further research is needed to test the model's statistical and clinical validity."

Treatment of avoidant personality disorder can employ various techniques, such as social skills training, cognitive therapy, and exposure treatment to gradually increase social contacts, group therapy for practicing social skills, and sometimes drug therapy.

A key issue in treatment is gaining and keeping the patient's trust, since people with avoidant personality disorder will often start to avoid treatment sessions if they distrust the therapist or fear rejection. The primary purpose of both individual therapy and social skills group training is for individuals with avoidant personality disorder to begin challenging their exaggerated negative beliefs about themselves.

Significant improvement in the symptoms of personality disorders is possible, with the help of treatment and individual effort.

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.

Despite recent initiatives to study psychopathology along dimensions of behavior and neurobiological indices, which would help refine a clearer picture of the development and treatment of externalizing disorders, the majority of research has examined specific mental disorders. Thus, best practices for many externalizing disorders are disorder-specific. For example, substance use disorders themselves are very heterogeneous and their best-evidenced treatment typically includes cognitive behavioral therapy, motivational interviewing, and a substance disorder-specific detoxification or psychotropic medication treatment component. The best-evidenced treatment for childhood conduct and externalizing problems more broadly, including youth with ADHD, ODD, and CD, is parent management training, a form of cognitive behavioral therapy. Additionally, individuals with ADHD, both youth and adults, are frequently treated with stimulant medications (or alternative psychotropic medications), especially if psychotherapy alone has not been effective in managing symptoms and impairment. Psychotherapy and medication interventions for individuals with severe, adult forms of antisocial behavior, such as antisocial personality disorder, have been mostly ineffective. An individual's comorbid psychopathology may also influences the course of treatment for an individual.

Being a personality disorder, which are usually chronic and long-lasting mental conditions, avoidant personality disorder is not expected to improve with time without treatment. It is a poorly studied personality disorder and in light of prevalence rates, societal costs, and the current state of research, AvPD qualifies as a neglected disorder.

Dependent personality disorder occurs in about 0.6% of the general population. The disorder is diagnosed more often in females than males; however, research suggests that this is largely due to behavioural differences in interviews and self-reporting rather than a difference in prevalence between the sexes. A 2004 twin study suggests a heritability of 0.81 for developing dependent personality disorder. Because of this, there is significant evidence that this disorder runs in families. Children and adolescents with a history of anxiety disorders and physical illnesses are more susceptible to acquiring this disorder.

Little is known about prognosis of untreated DID. It rarely, if ever, goes away without treatment, but symptoms may resolve from time to time or wax and wane spontaneously. Patients with mainly dissociative and posttraumatic symptoms face a better prognosis than those with comorbid disorders or those still in contact with abusers, and the latter groups often face lengthier and more difficult treatment. Suicidal ideation, failed suicide attempts, and self-harm also occur. Duration of treatment can vary depending on patient goals, which can extend from elimination of all alters to merely reducing inter-alter amnesia, but generally takes years.

The most effective treatment for an individual with conduct disorder is one that seeks to integrate individual, school, and family settings. Additionally, treatment should also seek to address familial conflict such as marital discord or maternal depression.

Treatment for OCPD includes psychotherapy, cognitive behavioral therapy, behavior therapy or self-help. Medication may be prescribed. In behavior therapy, a person with OCPD discusses with a psychotherapist ways of changing compulsions into healthier, productive behaviors. Cognitive analytic therapy is an effective form of behavior therapy.

Treatment is complicated if the person does not accept that they have OCPD, or believes that their thoughts or behaviors are in some sense correct and therefore should not be changed. Medication alone is generally not indicated for this personality disorder. Selective serotonin reuptake inhibitors (SSRIs) may be useful in addition to psychotherapy by helping the person with OCPD be less bogged down by minor details, and to lessen how rigid they are.

People with OCPD are three times more likely to receive individual psychotherapy than people with major depressive disorder. There are higher rates of primary care utilization. There are no known properly controlled studies of treatment options for OCPD. More research is needed to explore better treatment options.

The World Health Organization's ICD-10 lists dependent personality disorder as " Dependent personality disorder":

It is characterized by at least 4 of the following:

1. Encouraging or allowing others to make most of one's important life decisions;

2. Subordination of one's own needs to those of others on whom one is dependent, and undue compliance with their wishes;

3. Unwillingness to make even reasonable demands on the people one depends on;

4. Feeling uncomfortable or helpless when alone, because of exaggerated fears of inability to care for oneself;

5. Preoccupation with fears of being abandoned by a person with whom one has a close relationship, and of being left to care for oneself;

6. Limited capacity to make everyday decisions without an excessive amount of advice and reassurance from others.

Associated features may include perceiving oneself as helpless, incompetent, and lacking stamina.

Includes:

- Asthenic, inadequate, passive, and self-defeating personality (disorder)

It is a requirement of ICD-10 that a diagnosis of any specific personality disorder also satisfies a set of general personality disorder criteria.

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.