Dietary modifications may be of benefit to a small proportion of children with ADHD. A 2013 meta-analysis found less than a third of children with ADHD see some improvement in symptoms with free fatty acid supplementation or decreased eating of artificial food coloring. These benefits may be limited to children with food sensitivities or those who are simultaneously being treated with ADHD medications. This review also found that evidence does not support removing other foods from the diet to treat ADHD. A 2014 review found that an elimination diet results in a small overall benefit. A 2016 review stated that the use of a gluten-free diet as standard ADHD treatment is discouraged. Iron, magnesium and iodine may also have an effect on ADHD symptoms. There is a small amount of evidence that lower tissue zinc levels may be associated with ADHD. In the absence of a demonstrated zinc deficiency (which is rare outside of developing countries), zinc supplementation is not recommended as treatment for ADHD. However, zinc supplementation may reduce the minimum effective dose of amphetamine when it is used with amphetamine for the treatment of ADHD. There is evidence of a modest benefit of omega 3 fatty acid supplementation, but it is not recommended in place of traditional medication.

Once the patient and family have been educated about the nature, management and treatment of the disorder and a decision has been made to treat, the European ADHD Guidelines group recommends medication rather than behavioral training as the first treatment approach; and the UK's National Institute for Health and Clinical Excellence recommends medication as first line treatment for those with hyperkinesis/severe ADHD, and the provision of group parent-training in all cases of ADHD.

Stimulant medications are the pharmaceutical treatment of choice. They have at least some effect on symptoms in the short term in about 80% of people. Methylphenidate appears to improve symptoms as reported by teachers and parents. Stimulants may also reduce the risk of unintentional injuries in children with ADHD.

There are a number of non-stimulant medications, such as atomoxetine, bupropion, guanfacine, and clonidine that may be used as alternatives, or added to stimulant therapy. There are no good studies comparing the various medications; however, they appear more or less equal with respect to side effects. Stimulants appear to improve academic performance while atomoxetine does not. Atomoxetine, due to its lack of addiction liability, may be preferred in those who are at risk of recreational or compulsive stimulant use. There is little evidence on the effects of medication on social behaviors. , the long-term effects of ADHD medication have yet to be fully determined. Magnetic resonance imaging studies suggest that long-term treatment with amphetamine or methylphenidate decreases abnormalities in brain structure and function found in subjects with ADHD.

Guidelines on when to use medications vary by country, with the United Kingdom's National Institute for Health and Care Excellence recommending use for children only in severe cases, though for adults medication is a first-line treatment, while most United States guidelines recommend medications in most age groups. Medications are not recommended for preschool children. Underdosing of stimulants may occur and result in a lack of response or later loss of effectiveness. This is particularly common in adolescents and adults as approved dosing is based on school-aged children, causing some practitioners to use weight based or benefit based off-label dosing instead.

While stimulants and atomoxetine are usually safe, there are side-effects and contraindications to their use. A large overdose on ADHD stimulants is commonly associated with symptoms such as stimulant psychosis and mania; although very rare, at therapeutic doses these events appear to occur in approximately 0.1% of individuals within the first several weeks after starting amphetamine or methylphenidate therapy. Administration of an antipsychotic medication has been found to effectively resolve the symptoms of acute amphetamine psychosis. Regular monitoring has been recommended in those on long-term treatment. Stimulant therapy should be stopped periodically to assess continuing need for medication, decrease possible growth delay, and reduce tolerance. Long-term misuse of stimulant medications at doses above the therapeutic range for ADHD treatment is associated with addiction and dependence. Untreated ADHD, however, is also associated with elevated risk of substance use disorders and conduct disorders. The use of stimulants appears to either reduce this risk or have no effect on it. The safety of these medications in pregnancy is unclear.

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.

Approaches to the treatment of ODD include parent management training, individual psychotherapy, family therapy, cognitive behavioral therapy, and social skills training. According to the American Academy of Child and Adolescent Psychiatry, treatments for ODD are tailored specifically to the individual child, and different treatment techniques are applied for pre-schoolers and adolescents. Several preventative programs have had a positive effect on those at high risk for ODD. Both home visitation and programs such as Head Start have shown some effectiveness in preschool children. Social skills training, parent management training, and anger management programs have been used as prevention programs for school-age children at risk for ODD. For adolescents at risk for ODD, cognitive interventions, vocational training and academic tutoring have shown preventative effectiveness. There is also limited evidence that the atypical antipsychotic medication risperidone decreases aggression and conduct problems in youth with disruptive behavioral disorders, such as ODD.

Treatment is attempted through both cognitive behavioral therapy and psychotropic medication regimens, though the pharmaceutical options have shown limited success. Therapy aids in helping the patient recognize the impulses in hopes of achieving a level of awareness and control of the outbursts, along with treating the emotional stress that accompanies these episodes. Multiple drug regimens are frequently indicated for IED patients. Cognitive Relaxation and Coping Skills Therapy (CRCST) has shown preliminary success in both group and individual settings compared to waitlist control groups. This therapy consists of 12 sessions, the first three focusing on relaxation training, then cognitive restructuring, then exposure therapy. The final sessions focus on resisting aggressive impulses and other preventative measures.

Tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, fluvoxamine, and sertraline appear to alleviate some pathopsychological symptoms. GABAergic mood stabilizers and anticonvulsive drugs such as gabapentin, lithium, carbamazepine, and divalproex seem to aid in controlling the incidence of outbursts. Anxiolytics help alleviate tension and may help reduce explosive outbursts by increasing the provocative stimulus tolerance threshold, and are especially indicated in patients with comorbid obsessive-compulsive or other anxiety disorders. However, certain anxiolytics are known to "increase" anger and irritability in some individuals, especially benzodiazepines.

Impulsive behavior, and especially impulsive violence predisposition has been correlated to a low brain serotonin turnover rate, indicated by a low concentration of 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). This substrate appears to act on the suprachiasmatic nucleus in the hypothalamus, which is the target for serotonergic output from the dorsal and median raphe nuclei playing a role in maintaining the circadian rhythm and regulation of blood sugar. A tendency towards low 5-HIAA may be hereditary. A putative hereditary component to low CSF 5-HIAA and concordantly possibly to impulsive violence has been proposed. Other traits that correlate with IED are low vagal tone and increased insulin secretion. A suggested explanation for IED is a polymorphism of the gene for tryptophan hydroxylase, which produces a serotonin precursor; this genotype is found more commonly in individuals with impulsive behavior.

IED may also be associated with lesions in the prefrontal cortex, with damage to these areas, including the amygdala, increasing the incidence of impulsive and aggressive behavior and the inability to predict the outcomes of an individual's own actions. Lesions in these areas are also associated with improper blood sugar control, leading to decreased brain function in these areas, which are associated with planning and decision making. A national sample in the United States estimated that 16 million Americans may fit the criteria for IED.

Some treatments for internalizing disorders include antidepressants, electroconvulsive therapy, and psychotherapy.

ODD has an estimated lifetime prevalence of 10.2% (11.2% for males, 9.2% for females).

Externalizing disorders are frequently comorbid or co-occurring with other disorders. Individuals who have the co-occurrence of more than one externalizing disorder have homotypic comorbidity, whereas individuals who have co-occurring externalizing and Internalizing disorders have heterotypic comorbidity. It is not uncommon for children with early externalizing problems to develop both internalizing and further externalizing problems across the lifespan.

Research on treating BDD is limited. Yet anti-depressant medication, such as selective serotonin reuptake inhibitors (SSRIs), and cognitive-behavioral therapy (CBT) are considered effective. SSRIs can help relieve obsessive-compulsive and delusional traits, while cognitive-behavioral therapy can help patients recognize faulty thought patterns. Before treatment, it can help to provide psychoeducation, as with self-help books and support websites.

The rate in school age children is thought to be about 1.5%, compared with an estimated 5.3% for ADHD.

Impulse-control disorders have two treatment options: psychosocial and pharmacological. Treatment methodology is informed by the presence of comorbid conditions.

In the case of pathological gambling, along with fluvoxamine, clomipramine has been shown effective in the treatment, with reducing the problems of pathological gambling in a subject by up to 90%. Whereas in trichotillomania, the use of clomipramine has again been found to be effective, fluoxetine has not produced consistent positive results. Fluoxetine, however, has produced positive results in the treatment of pathological skin picking disorder, although more research is needed to conclude this information. Fluoxetine has also been evaluated in treating IED and demonstrated significant improvement in reducing frequency and severity of impulsive aggression and irritability in a sample of 100 subjects who were randomized into a 14-week, double-blind study. Despite a large decrease in impulsive aggression behavior from baseline, only 44% of fluoxetine responders and 29% of all fluoxetine subjects were considered to be in full remission at the end of the study. Paroxetine has shown to be somewhat effective although the results are inconsistent. Another medication, escitalopram, has shown to improve the condition of the subjects of pathological gambling with anxiety symptoms. The results suggest that although SSRIs have shown positive results in the treatment of pathological gambling, inconsistent results with the use of SSRIs have been obtained which might suggest a neurological heterogeneity in the impulse-control disorder spectrum.

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 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).

There is no known "cure" for PDD-NOS, but there are interventions that can have a positive influence. Early and intensive implementation of evidence-based practices and interventions are generally believed to improve outcomes. Most of these are individualized special education strategies rather than medical or pharmaceutical treatment; the best outcomes are achieved when a team approach among supporting individuals is utilized.

Some of the more common therapies and services include:

- Visual and environmental supports, visual schedules

- Applied behavior analysis

- Discrete trial instruction (part of applied behavior analysis)

- Social stories and comic strip conversations

- Physical and occupational therapy

Psychotherapy, more specifically, cognitive behavioral therapy (CBT), is the most widely used form of treatment for Somatic symptom disorder. In 2016, a randomized 12-week study suggested steady and significant improvement in health anxiety measures with cognitive behavioral therapy compared to the control group.

CBT can help in some of the following ways:

- Learn to reduce stress

- Learn to cope with physical symptoms

- Learn to deal with depression and other psychological issues

- Improve quality of life

- Reduce preoccupation with symptom

Moreover, brief psychodynamic interpersonal psychotherapy (PIT) for patients with multisomatoform disorder has shown its long-term efficacy for improving the physical quality of life in patients with multiple, difficult-to-treat, medically unexplained symptoms.

Antidepressant medication has also been used to treat some of the symptoms of depression and anxiety that are common among people who have somatic symptom disorder. Medications will not cure somatic symptom disorder, but can help the treatment process when combined with CBT.

An internalizing disorder is one type of emotional and behavioral disorder, along with externalizing disorders, and low incidence disorders. One who suffers from an internalizing disorder will keep their problems to themselves, or internalize the problems.

As with most mental disorders, BDD's causation is likely intricate, altogether biopsychosocial, through an interaction of multiple factors, including genetic, developmental, psychological, social, and cultural. BDD usually develops during early adolescence, although many patients note earlier trauma, abuse, neglect, teasing, or bullying. Though twin studies on BDD are few, one estimated its heritability at 43%. Yet BDD's causation may also involve introversion, negative body image, perfectionism, heightened aesthetic sensitivity, and childhood abuse and neglect. Media influence has also been identified as a factor causing poor body image.

Separation anxiety disorder

- Cognitive behavioral therapy is often used to treat separation anxiety disorder. Family therapy may also be helpful to get to the core of the issue. Systemic desensitization techniques are usually used to help the child get used to being comfortable away from home.

Selective mutism

- It is important not to "enable" the child with selective mutism by allowing them to remain silent in the social settings that they are uncomfortable in. Both parents and teachers need to be involved in the treatment of selective mutism. The most important factor to remember is that the child does not have a speech disorder; it is an anxiety disorder.

Reactive attachment disorder of infancy or early childhood

- Treatment almost always involves the child and his or her parents or caregivers. Parents may need to take parenting skills classes and attend family therapy with the child. Individual therapy with the child and therapist is effective. Another technique is keeping close physical contact between the child and his or her parents.

Stereotypic movement disorder

- Behavioral techniques and psychotherapy are the most effective treatment for children with this disorder. It is important to change the child's environment so that they are unable to harm themselves. Medication is also effective.

Medications are used to address certain behavioral problems; therapy for children with PDD should be specialized according to the child's specific needs.

Some children with PDD benefit from specialized classrooms in which the class size is small and instruction is given on a one-to-one basis. Others function well in standard special education classes or regular classes with support. Early intervention, including appropriate and specialized educational programs and support services, play a critical role in improving the outcome of individuals with PDD.

There are people such as Thomas Szasz and Peter Breggin who say child psychiatry should be made illegal because behaviours are not diseases. They believe psychiatric drugging is a form of child abuse.

The recommended treatment for adjustment disorder is psychotherapy. The goal of psychotherapy is symptom relief and behavior change. Anxiety may be presented as "a signal from the body" that something in the patient's life needs to change. Treatment allows the patient to put his or her distress or rage into words rather than into destructive actions. Individual therapy can help a person gain the support they need, identify abnormal responses and maximize the use of the individual's strengths. Counseling, psychotherapy, crisis intervention, family therapy, behavioral therapy and self-help group treatment are often used to encourage the verbalization of fears, anxiety, rage, helplessness, and hopelessness. Sometimes small doses of antidepressants and anxiolytics are used in addition to other forms of treatment. In patients with severe life stresses and a significant anxious component, benzodiazepines are used, although non-addictive alternatives have been recommended for patients with current or past heavy alcohol use, because of the greater risk of dependence. Tianeptine, alprazolam, and mianserin were found to be equally effective in patients with AD with anxiety. Additionally, antidepressants, antipsychotics (rarely) and stimulants (for individuals who became extremely withdrawn) have been used in treatment plans.

There has been little systematic research regarding the best way to manage individuals with an adjustment disorder. Because natural recovery is the norm, it has been argued that there is no need to intervene unless levels of risk or distress are high. However, for some individuals treatment may be beneficial. AD sufferers with depressive and/or anxiety symptoms may benefit from treatments usually used for depressive and/or anxiety disorders. One study found that AD sufferers received similar interventions to those with other psychiatric diagnoses, including psychological therapy and medication. Another study found that AD responded better than major depression to antidepressants. Given the absence of a meaningful evidence base for the treatment of AD "per se", watchful waiting should be considered initially; if symptoms are not improving or causing the sufferer marked distress then treatment should be directed at the predominating symptoms.

In addition to professional help, parents and caregivers can help their children with their difficulty adjusting by:

- offering encouragement to talk about his/her emotions

- offering support and understanding

- reassuring the child that their reactions are normal

- involving the child's teachers to check on their progress in school

- letting the child make simple decisions at home, such as what to eat for dinner or what show to watch on TV

- having the child engage in a hobby or activity they enjoy

There are several different classes of pharmacological treatment agents that have some support for treating excoriation disorder: (1) SSRIs; (2) opioid antagonists; and (3) glutamatergic agents. In addition to these classes of drugs, some other pharmacological products have been tested in small trials as well.

SSRIs have shown to be effective in the treatment of OCD and this has provided an argument in favor of treating excoriation disorder with the same therapy. Unfortunately, the clinical studies have not provided clear support for this, because there have not been large double-blind placebo-controlled trials of SSRI therapy for excoriation disorder.

Review of treatment of excoriation disorder have shown that the following medications may be effective in reducing picking behavior: doxepin, clomipramine, naltrexone, pimozide, and olanzapine. Small studies of fluoxetine, an SSRI, in treating excoriation disorder showed that the drug reduced certain aspects of skin picking, as compared to placebo, but full remission was not observed. One small study of patients with excoriation disorder treated with citalopram, another SSRI, showed that those that took the drug significantly reduced their scores on the Yale-Brown Obsessive Compulsive Scale compared to placebo, but that there was no significant decrease on the visual-analog scale of picking behavior.

While there have been no human studies of opioid antagonists for the treatment of excoriation disorder, there have been studies showing that these products can reduce self-chewing in dogs with acral lick, which some have proposed is a good animal model for the body-focused repetitive behavior. Furthermore, there have been case reports that support the use of these opioid antagonists to treat excoriation disorder. Opioid antagonists work by affecting dopamine circuitry, thereby decreasing the pleasurable effects of picking.

Another class of possible pharmacological treatments are glutamatergic agents such as n-acetyl cysteine (NAC). These products have shown some ability to reduce other problematic behaviors such as cocaine addiction and trichotillomania. Some case studies and some small studies of NAC have shown a decrease in picking by treatment with NAC, as compared to placebo.

Excoriation disorder, and trichotillomania have been treated with inositol.

Topiramate, an anti-epileptic drug, has been used to treat excoriation disorder; in a small study of individuals with Prader–Willi syndrome, it was found to reduce skin picking.