Pediatricians are often the first health professionals to assess and raise suspicions of RAD in children with the disorder. The initial presentation varies according to the child's developmental and chronological age, although it always involves a disturbance in social interaction. Infants up to about 18–24 months "may" present with non-organic failure to thrive and display abnormal responsiveness to stimuli. Laboratory investigations will be unremarkable barring possible findings consistent with malnutrition or dehydration, while serum growth hormone levels will be normal or elevated.

The core feature is severely inappropriate social relating by affected children. This can manifest itself in two ways:

1. Indiscriminate and excessive attempts to receive comfort and affection from any available adult, even relative strangers (older children and adolescents may also aim attempts at peers).

2. Extreme reluctance to initiate or accept comfort and affection, even from familiar adults, especially when distressed.

While RAD is likely to occur in relation to neglectful and abusive treatment, automatic diagnoses on this basis alone cannot be made, as children can form stable attachments and social relationships despite marked abuse and neglect.

The name of the disorder emphasizes problems with attachment but the criteria includes symptoms such as failure to thrive, a lack of developmentally appropriate social responsiveness, apathy, and onset before 8 months.

According to Adam und Breithaupt-Peters personality development disorders are defined as complex disorders

- which show similarity to a certain type of personality disorder in adulthood

- which persist over a long period of time (more than a year) and show a tendency towards being chronic

- which have a severe negative impact on more than one important area of functioning or social life

- which show resistance to traditional educational and therapeutic treatment methods

- which result in a reduced insight into or ignorance of the own problem behavior. The family usually suffers more than the child or adolescent and has a hard time dealing with the diminished introspection.

- which make positive interactions between the children/adolescents and other people merely impossible. Instead social collisions are part of everyday life.

- which threaten the social integration of the young person into a social life and might result in an emotional disability.

Typical deficiencies may include problems identifying, processing, describing, and working with one's own feelings, often marked by a lack of understanding of the feelings of others; difficulty distinguishing between feelings and the bodily sensations of emotional arousal; confusion of physical sensations often associated with emotions; few dreams or fantasies due to restricted imagination; and concrete, realistic, logical thinking, often to the exclusion of emotional responses to problems. Those who have alexithymia also report very logical and realistic dreams, such as going to the store or eating a meal. Clinical experience suggests it is the structural features of dreams more than the ability to recall them that best characterizes alexithymia.

Some alexithymic individuals may appear to contradict the above-mentioned characteristics because they can experience chronic dysphoria or manifest outbursts of crying or rage. However, questioning usually reveals that they are quite incapable of describing their feelings or appear confused by questions inquiring about specifics of feelings.

According to Henry Krystal, individuals suffering from alexithymia think in an operative way and may appear to be superadjusted to reality. In psychotherapy, however, a cognitive disturbance becomes apparent as patients tend to recount trivial, chronologically ordered actions, reactions, and events of daily life with monotonous detail. In general, these individuals lack imagination, intuition, empathy, and drive-fulfillment fantasy, especially in relation to objects. Instead, they seem oriented toward things and even treat themselves as robots. These problems seriously limit their responsiveness to psychoanalytic psychotherapy; psychosomatic illness or substance abuse is frequently exacerbated should these individuals enter psychotherapy.

A common misconception about alexithymia is that affected individuals are totally unable to express emotions verbally and that they may even fail to acknowledge that they experience emotions. Even before coining the term, Sifneos (1967) noted patients often mentioned things like anxiety or depression. The distinguishing factor was their inability to elaborate beyond a few limited adjectives such as "happy" or "unhappy" when describing these feelings. The core issue is that people with alexithymia have poorly differentiated emotions limiting their ability to distinguish and describe them to others. This contributes to the sense of emotional detachment from themselves and difficulty connecting with others, making alexithymia negatively associated with life satisfaction even when depression and other confounding factors are controlled for.

A personality development disorder is an inflexible and pervasive pattern of inner experience and behavior in children and adolescents, that markedly deviates from the expectations of the individual's culture. Personality development disorder is not recognized as a mental disorder in any of the medical manuals, such as the ICD-10 or the DSM-IV, neither is it part of the proposed revision of this manual, the DSM-5. DSM-IV allows the diagnosis of personality disorders in children and adolescents only as an exception.

This diagnosis is currently proposed by a few authors in Germany. The term personality "development" disorder is used to emphasize the changes in personality development which might still take place and the open outcome during development. Personality development disorder is considered to be a childhood risk factor or early stage of a later personality disorder in adulthood.

Adults usually show personality patterns over a long duration of time. Children and adolescents however still show marked changes in personality development. Some of these children and adolescents have a hard time developing their personalities in an ordinary way. DSM-IV states, for example, that children and adolescents are at higher risk to develop an antisocial personality disorder if they showed signs of conduct disorder and attention deficit disorder before the age of 10. This led Adam & Breithaupt-Peters (2010) to the idea that these children and adolescents need to be looked at more carefully. The therapy which these children and adolescents need might be more intense and maybe even different from looking at the disorders traditionally. The concept of personality development disorders also focuses on the severity of the disorder and the poor prognosis. An early diagnosis might help to get the right treatment at an early stage and thus might help to prevent a personality disorder outcome in adulthood.

The diagnosis of PTSD was originally developed for adults who had suffered from a single event trauma, such as rape, or a traumatic experience during a war. However, the situation for many children is quite different. Children can suffer chronic trauma such as maltreatment, family violence, and a disruption in attachment to their primary caregiver. In many cases, it is the child's caregiver who caused the trauma. The diagnosis of PTSD does not take into account how the developmental stages of children may affect their symptoms and how trauma can affect a child’s development.

The term developmental trauma disorder (DTD) has also been suggested. This developmental form of trauma places children at risk for developing psychiatric and medical disorders. Bessel van der Kolk explains DTD as numerous encounters with interpersonal trauma such as physical assault, sexual assault, violence or death. It can also be characterized by subjective events like betrayal, defeat or shame.

Repeated traumatization during childhood leads to symptoms that differ from those described for PTSD. Cook and others describe symptoms and behavioural characteristics in seven domains:

- "Attachment" – "problems with relationship boundaries, lack of trust, social isolation, difficulty perceiving and responding to others' emotional states"

- "Biology" – "sensory-motor developmental dysfunction, sensory-integration difficulties, somatization, and increased medical problems"

- "Affect or emotional regulation" – "poor affect regulation, difficulty identifying and expressing emotions and internal states, and difficulties communicating needs, wants, and wishes"

- "Dissociation" – "amnesia, depersonalization, discrete states of consciousness with discrete memories, affect, and functioning, and impaired memory for state-based events"

- "Behavioural control" – "problems with impulse control, aggression, pathological self-soothing, and sleep problems"

- "Cognition" – "difficulty regulating attention, problems with a variety of 'executive functions' such as planning, judgement, initiation, use of materials, and self-monitoring, difficulty processing new information, difficulty focusing and completing tasks, poor object constancy, problems with 'cause-effect' thinking, and language developmental problems such as a gap between receptive and expressive communication abilities."

- "Self-concept" – "fragmented and disconnected autobiographical narrative, disturbed body image, low self-esteem, excessive shame, and negative internal working models of self".

According to Michael First of the DSM-5 working committee the focus of a relational disorder, in contrast to other DSM-IV disorders, "is on the relationship rather than on any one individual in the relationship".

Relational disorders involve two or more individuals and a disordered "juncture", whereas typical Axis I psychopathology describes a disorder at the individual level. An additional criterion for a relational disorder is that the disorder cannot be due solely to a problem in one member of the relationship, but requires pathological interaction from each of the individuals involved in the relationship.

For example, if a parent is withdrawn from one child but not another, the could be attributed to a relational disorder. In contrast, if a parent is withdrawn from both children, the dysfunction may be more appropriately attributable to a disorder at the individual level.

First states that "relational disorders share many elements in common with other disorders: there are distinctive features for classification; they can cause clinically significant impairment; there are recognizable clinical courses and patterns of comorbidity; they respond to specific treatments; and they can be prevented with early interventions. Specific tasks in a proposed research agenda: develop assessment modules; determine the clinical utility of relational disorders; determine the role of relational disorders in the etiology and maintenance of individual disorders; and consider aspects of relational disorders that might be modulated by individual disorders."

The proposed new diagnosis defines a relational disorder as "persistent and painful patterns of feelings, behaviors, and perceptions" among two or more people in an important personal relationship, such a husband and wife, or a parent and children.

According to psychiatrist Darrel Regier, MD, some psychiatrists and other therapists involved in couples and marital counseling have recommended that the new diagnosis be considered for possible incorporation into the Diagnostic and Statistical Manual of Mental Disorders (DSM IV).

Reactive attachment disorder (RAD) is described in clinical literature as a severe and relatively uncommon disorder that can affect children. RAD is characterized by markedly disturbed and developmentally inappropriate ways of relating socially in most contexts. It can take the form of a persistent failure to initiate or respond to most social interactions in a developmentally appropriate way—known as the "inhibited form". Due to recent revision in the DSM-5 the "disinhibited form" is now considered a separate diagnosis named "Disinhibited attachment disorder".

RAD arises from a failure to form normal attachments to primary caregivers in early childhood. Such a failure could result from severe early experiences of neglect, abuse, abrupt separation from caregivers between the ages of six months and three years, frequent change of caregivers, or a lack of caregiver responsiveness to a child's communicative efforts. Not all, or even a majority of such experiences, result in the disorder. It is differentiated from pervasive developmental disorder or developmental delay and from possibly comorbid conditions such as intellectual disability, all of which can affect attachment behavior. The criteria for a diagnosis of a reactive attachment "disorder" are very different from the criteria used in assessment or categorization of attachment "styles" such as insecure or disorganized attachment.

Children with RAD are presumed to have grossly disturbed internal working models of relationships that may lead to interpersonal and behavioral difficulties in later life. There are few studies of long-term effects, and there is a lack of clarity about the presentation of the disorder beyond the age of five years. However, the opening of orphanages in Eastern Europe following the end of the Cold War in the early-1990s provided opportunities for research on infants and toddlers brought up in very deprived conditions. Such research broadened the understanding of the prevalence, causes, mechanism and assessment of disorders of attachment and led to efforts from the late-1990s onwards to develop treatment and prevention programs and better methods of assessment. Mainstream theorists in the field have proposed that a broader range of conditions arising from problems with attachment should be defined beyond current classifications.

Mainstream treatment and prevention programs that target RAD and other problematic early attachment behaviors are based on attachment theory and concentrate on increasing the responsiveness and sensitivity of the caregiver, or if that is not possible, placing the child with a different caregiver. Most such strategies are in the process of being evaluated. Mainstream practitioners and theorists have presented significant criticism of the diagnosis and treatment of alleged reactive attachment disorder or the theoretically baseless "attachment disorder" within the controversial form of psychotherapy commonly known as attachment therapy. Attachment therapy has a scientifically unsupported theoretical base and uses diagnostic criteria or symptom lists markedly different to criteria under ICD-10 or DSM-IV-TR, or to attachment behaviors. A range of treatment approaches are used in attachment "therapy", some of which are physically and psychologically coercive, and considered to be to attachment "theory". Many constitute abuse.

Alexithymia is considered to be a personality trait that places affected individuals at risk for other medical and psychiatric disorders while reducing the likelihood that these individuals will respond to conventional treatments for the other conditions. Alexithymia is not classified as a mental disorder in the fourth edition of the "Diagnostic and Statistical Manual of Mental Disorders". It is a dimensional personality trait that varies in severity from person to person. A person's alexithymia score can be measured with questionnaires such as the Toronto Alexithymia Scale (TAS-20), the Bermond-Vorst Alexithymia Questionnaire (BVAQ), the Online Alexithymia Questionnaire (OAQ-G2) or the Observer Alexithymia Scale (OAS). It is distinct from the psychiatric personality disorders, such as antisocial personality disorder or borderline personality disorder, with which it shares some characteristics, and is likewise distinct from the abnormal conditions of sociopathy or psychopathy.

Alexithymia is defined by:

1. difficulty identifying feelings and distinguishing between feelings and the bodily sensations of emotional arousal

2. difficulty describing feelings to other people

3. constricted imaginal processes, as evidenced by a scarcity of fantasies

4. a stimulus-bound, externally oriented cognitive style.

In studies of the general population the degree of alexithymia was found to be influenced by age, but not by gender; the rates of alexithymia in healthy controls have been found at: 8.3%; 4.7%; 8.9%; and 7%. Thus, several studies have reported that the prevalence rate of alexithymia is less than 10%. A less common finding suggests that there may be a higher prevalence of alexithymia amongst males than females, which may be accounted for by difficulties some males have with "describing feelings", but not by difficulties in "identifying feelings" in which males and females show similar abilities.

Psychologist R. Michael Bagby and psychiatrist Graeme J. Taylor have argued that the alexithymia construct is strongly related (negatively) to the concepts of psychological mindedness and emotional intelligence and there is "strong empirical support for alexithymia being a stable personality trait rather than just a consequence of psychological distress". Other opinions differ and can show evidence that it may be state-dependent.

Bagby and Taylor also suggest that there may be two kinds of alexithymia, "primary alexithymia" which is an enduring psychological trait that does not alter over time, and "secondary alexithymia" which is state-dependent and disappears after the evoking stressful situation has changed. These two manifestations of alexithymia are otherwise called "trait" or "state" alexithymia.

Adults with C-PTSD have sometimes experienced prolonged interpersonal traumatization as children as well as prolonged trauma as adults. This early injury interrupts the development of a robust sense of self and of others. Because physical and emotional pain or neglect was often inflicted by attachment figures such as caregivers or older siblings, these individuals may develop a sense that they are fundamentally flawed and that others cannot be relied upon.

This can become a pervasive way of relating to others in adult life described as insecure attachment. The diagnosis of dissociative disorder and PTSD in the current DSM-5 (2013) do not include insecure attachment as a symptom. Individuals with Complex PTSD also demonstrate lasting personality disturbances with a significant risk of revictimization.

Six clusters of symptoms have been suggested for diagnosis of C-PTSD:

- alterations in regulation of affect and impulses;

- alterations in attention or consciousness;

- alterations in self-perception;

- alterations in relations with others;

- somatization;

- alterations in systems of meaning.

Experiences in these areas may include:

- Difficulties regulating emotions, including symptoms such as persistent dysphoria, chronic suicidal preoccupation, self injury, explosive or extremely inhibited anger (may alternate), or compulsive or extremely inhibited sexuality (may alternate).

- Variations in consciousness, including forgetting traumatic events (i.e., psychogenic amnesia), reliving experiences (either in the form of intrusive PTSD symptoms or in ruminative preoccupation), or having episodes of dissociation.

- Changes in self-perception, such as a chronic and pervasive sense of helplessness, paralysis of initiative, shame, guilt, self-blame, a sense of defilement or stigma, and a sense of being completely different from other human beings.

- Varied changes in the perception of the perpetrator, such as attributing total power to the perpetrator, becoming preoccupied with the relationship to the perpetrator, including a preoccupation with revenge, idealization or paradoxical gratitude, seeking approval from the perpetrator, a sense of a special relationship with the perpetrator or acceptance of the perpetrator's belief system or rationalizations.

- Alterations in relations with others, including isolation and withdrawal, persistent distrust, anger and hostility, a repeated search for a rescuer, disruption in intimate relationships and repeated failures of self-protection.

- Loss of, or changes in, one's system of meanings, which may include a loss of sustaining faith or a sense of hopelessness and despair.

- Disconnection from surroundings accompanied by feelings of terror and confusion.

One of the symptoms of conduct disorder is a lower level of fear. Research performed on the impact of toddlers exposed to fear and distress shows that negative emotionality (fear) predicts toddlers' empathy-related response to distress. The findings support that if a caregiver is able to respond to infant cues, the toddler has a better ability to respond to fear and distress. If a child does not learn how to handle fear or distress the child will be more likely to lash out at other children. If the caregiver is able to provide therapeutic intervention teaching children at risk better empathy skills, the child will have a lower incident level of conduct disorder.

Avoidant individuals often choose jobs of isolation so that they do not have to interact with the public regularly, due to their anxiety and fear of embarrassing themselves in front of others. Some with this disorder may fantasize about idealized, accepting, and affectionate relationships, due to their desire to belong. Individuals with the disorder tend to describe themselves as uneasy, anxious, lonely, unwanted and isolated from others. They often feel themselves unworthy of the relationships they desire, so they shame themselves from ever attempting to begin them.

People with avoidant personality disorder are preoccupied with their own shortcomings and form relationships with others only if they believe they will not be rejected. Loss and social rejection are so painful that these individuals will choose to be alone rather than risk trying to connect with others (see rejection sensitivity). They often view themselves with contempt, while showing an increased inability to identify traits within themselves that are generally considered as positive within their societies.

- Hypersensitivity to rejection and criticism

- Self-imposed social isolation

- Extreme shyness or anxiety in social situations, though the person feels a strong desire for close relationships

- Avoids physical contact because it has been associated with an unpleasant or painful stimulus

- Feelings of inadequacy

- Drastically reduced or absent self-esteem

- Self-loathing, autophobia or self-harm

- Mistrust of others or oneself; exhibits heightened self-doubt

- Emotional distancing related to intimacy

- Highly self-conscious

- Self-critical about their problems relating to others

- Heightened attachment-related anxiety, which may include a fear of abandonment

- Problems in occupational functioning

- Lonely self-perception, although others may find the relationship with them meaningful

- Feeling inferior to others

- Substance abuse and/or dependence

- In some extreme cases, agoraphobia

- Uses fantasy as a form of escapism to interrupt painful thoughts

The likely course and outcome of mental disorders varies and is dependent on numerous factors related to the disorder itself, the individual as a whole, and the social environment. Some disorders are transient, while others may be more chronic in nature.

Even those disorders often considered the most serious and intractable have varied courses i.e. schizophrenia, psychotic disorders, and personality disorders. Long-term international studies of schizophrenia have found that over a half of individuals recover in terms of symptoms, and around a fifth to a third in terms of symptoms and functioning, with some requiring no medication. At the same time, many have serious difficulties and support needs for many years, although "late" recovery is still possible. The World Health Organization concluded that the long-term studies' findings converged with others in "relieving patients, carers and clinicians of the chronicity paradigm which dominated thinking throughout much of the 20th century."

Around half of people initially diagnosed with bipolar disorder achieve syndromal recovery (no longer meeting criteria for the diagnosis) within six weeks, and nearly all achieve it within two years, with nearly half regaining their prior occupational and residential status in that period. However, nearly half go on to experience a new episode of mania or major depression within the next two years. Functioning has been found to vary, being poor during periods of major depression or mania but otherwise fair to good, and possibly superior during periods of hypomania in Bipolar II.

Mental retardation is coded on Axis II of the DSM-IV-TR. The diagnostic criteria necessary in order to diagnose intellectual disability consists of:

There are varying degrees of intellectual disability, which are identified by an IQ test.

Mental retardation, Severity Unspecified: This unspecified diagnosis is given when there is a strong assumption that the child is mentally retarded, but cannot be tested because the individual is too impaired, not willing to take the IQ test or is an infant.

People with HPD are usually high-functioning, both socially and professionally. They usually have good social skills, despite tending to use them to manipulate others into making them the center of attention. HPD may also affect a person's social and/or romantic relationships, as well as their ability to cope with losses or failures. They may seek treatment for clinical depression when romantic (or other close personal) relationships end.

Individuals with HPD often fail to see their own personal situation realistically, instead dramatizing and exaggerating their difficulties. They may go through frequent job changes, as they become easily bored and may prefer withdrawing from frustration (instead of facing it). Because they tend to crave novelty and excitement, they may place themselves in risky situations. All of these factors may lead to greater risk of developing clinical depression.

Additional characteristics may include:

- Exhibitionist behavior

- Constant seeking of reassurance or approval

- Excessive sensitivity to criticism or disapproval

- Pride of own personality and unwillingness to change, viewing any change as a threat

- Inappropriately seductive appearance or behavior of a sexual nature

- Using somatic symptoms (of physical illness) to garner attention

- A need to be the center of attention

- Low tolerance for frustration or delayed gratification

- Rapidly shifting emotional states that may appear superficial or exaggerated to others

- Tendency to believe that relationships are more intimate than they actually are

- Making rash decisions

- Blaming personal failures or disappointments on others

- Being easily influenced by others, especially those who treat them approvingly

- Being overly dramatic and emotional

Some people with histrionic traits or personality disorder change their seduction technique into a more maternal or paternal style as they age.

Ganser syndrome was once considered a separate factitious disorder. It is a disorder of extreme stress or an organic condition. The patient suffers from approximation or giving absurd answers to simple questions. The syndrome is sometimes diagnosed as merely malingering—however, it is more often defined as a factitious disorder. This has been seen in prisoners following solitary confinement, and the symptoms are consistent in different prisons, though the patients do not know one another.

Symptoms include a clouding of consciousness, somatic conversion symptoms, confusion, stress, loss of personal identity, echolalia, and echopraxia. Individuals also give approximate answers to simple questions such as, "How many legs on a cat?" "Three"; "What's the day after Wednesday?" "Friday"; and so on. The disorder is extraordinarily rare with fewer than 100 recorded cases. While individuals of all backgrounds have been reported with the disorder, there is a higher inclination towards males (75% or more). The average age of those with Ganser syndrome is 32, though it stretches from ages 15–62 years old.

A mnemonic that can be used to remember the characteristics of histrionic personality disorder is shortened as "PRAISE ME":

- Provocative (or seductive) behavior

- Relationships are considered more intimate than they actually are

- Attention-seeking

- Influenced easily by others or circumstances

- Speech (style) wants to impress; lacks detail

- Emotional lability; shallowness

- Make-up; physical appearance is used to draw attention to self

- Exaggerated emotions; theatrical

Conversion disorder is now contained under the umbrella term functional neurological symptom disorder. In cases of conversion disorder, there is a psychological stressor.

The diagnostic criteria for functional neurological symptom disorder, as set out in DSM-V, are:

Specify type of symptom or deficit as:

- With weakness or paralysis

- With abnormal movement (e.g. tremor, dystonic movement, myoclonus, gait disorder)

- With swallowing symptoms

- With speech symptoms (e.g. dysphonia, slurred speech)

- With attacks or seizures

- With amnesia or memory loss

- With special sensory symptom (e.g. visual, olfactory, or hearing disturbance)

- With mixed symptoms.

Specify if:

- Acute episode: symptoms present for less than six months

- Persistent: symptoms present for six months or more.

Specify if:

- Psychological stressor (conversion disorder)

- No psychological stressor (functional neurological symptom disorder)

Emotional and behavioral disorders (EBD; sometimes called emotional disturbance or serious emotional disturbance) refer to a disability classification used in educational settings that allows educational institutions to provide special education and related services to students that have poor social or academic adjustment that cannot be better explained by biological abnormalities or a developmental disability.

The classification is often given to students that need individualized behavior supports to receive a free and appropriate public education, but would not be eligible for an individualized education program under another disability category of the Individuals with Disabilities Education Act (IDEA).

Factitious disorder should be distinguished from somatic symptom disorder (formerly called somatization disorder), in which the patient is truly experiencing the symptoms and has no intention to deceive.

In conversion disorder (previously called hysteria), a neurological deficit appears with no organic cause. The patient, again, is truly experiencing the symptoms and signs and has no intention to deceive.

The differential also includes body dysmorphic disorder and pain disorder.

Conduct disorder (CD) is a mental disorder diagnosed in childhood or adolescence that presents itself through a repetitive and persistent pattern of behavior in which the basic rights of others or major age-appropriate norms are violated. These behaviors are often referred to as "antisocial behaviors." It is often seen as the precursor to antisocial personality disorder, which is per definition not diagnosed until the individual is 18 years old.

Conduct disorder is estimated to affect 51.1 million people globally as of 2013.

Conversion disorder begins with some stressor, trauma, or psychological distress. Usually the physical symptoms of the syndrome affect the senses or movement. Common symptoms include blindness, partial or total paralysis, inability to speak, deafness, numbness, difficulty swallowing, incontinence, balance problems, seizures, tremors, and difficulty walking. These symptoms are attributed to conversion disorder when a medical explanation for the afflictions cannot be found. Symptoms of conversion disorder usually occur suddenly. Conversion disorder is typically seen in individuals aged 10 to 35, and affects between 0.011% and 0.5% of the general population.

Conversion disorder can present with motor or sensory symptoms including any of the following:

Motor symptoms or deficits:

- Impaired coordination or balance

- Weakness/paralysis of a limb or the entire body (hysterical paralysis or motor conversion disorders)

- Impairment or loss of speech (hysterical aphonia)

- Difficulty swallowing (dysphagia) or a sensation of a lump in the throat

- Urinary retention

- Psychogenic non-epileptic seizures or convulsions

- Persistent dystonia

- Tremor, myoclonus or other movement disorders

- Gait problems (astasia-abasia)

- Loss of consciousness (fainting)

Sensory symptoms or deficits:

- Impaired vision (hysterical blindness), double vision

- Impaired hearing (deafness)

- Loss or disturbance of touch or pain sensation

Conversion symptoms typically do not conform to known anatomical pathways and physiological mechanisms. It has sometimes been stated that the presenting symptoms tend to reflect the patient's own understanding of anatomy and that the less medical knowledge a person has, the more implausible are the presenting symptoms. However, no systematic studies have yet been performed to substantiate this statement.

A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitting, or occur as a single episode. Many disorders have been described, with signs and symptoms that vary widely between specific disorders. Such disorders may be diagnosed by a mental health professional.

The causes of mental disorders are often unclear. Theories may incorporate findings from a range of fields. Mental disorders are usually defined by a combination of how a person behaves, feels, perceives, or thinks. This may be associated with particular regions or functions of the brain, often in a social context. A mental disorder is one aspect of mental health. Cultural and religious beliefs, as well as social norms, should be taken into account when making a diagnosis.

Services are based in psychiatric hospitals or in the community, and assessments are carried out by psychiatrists, psychologists, and clinical social workers, using various methods but often relying on observation and questioning. Treatments are provided by various mental health professionals. Psychotherapy and psychiatric medication are two major treatment options. Other treatments include social interventions, peer support, and self-help. In a minority of cases there might be involuntary detention or treatment. Prevention programs have been shown to reduce depression.

Common mental disorders include depression, which affects about 400 million, dementia which affects about 35 million, and schizophrenia, which affects about 21 million people globally. Stigma and discrimination can add to the suffering and disability associated with mental disorders, leading to various social movements attempting to increase understanding and challenge social exclusion.

People with hypersexual disorder experience multiple, unsuccessful attempts to control or diminish the amount of time spent engaging in sexual fantasies, urges, and behaviors in response to dysphoric mood states or stressful life events.

For a valid diagnosis of hypersexual disorder to be established, symptoms must persist for a period of at least 6 months and occur independently of a use mania or a medical condition.

As it has already been mentioned, the organic personality disorder is included in a wide group of personality and behavioural disorders. This mental health disorder can be caused by disease, brain damages or dysfunctions in specific brain areas in frontal lobe. The most common reason for this profound change in personality is the traumatic brain injury (TBI). Children, whose brain areas have injured or damaged, may present Attention Deficit Hyperactivity Disorder (ADHD), oppositional defiant disorder (ODD) and organic personality disorder. Moreover, this disorder is characterised as "frontal lobe syndrome". This characteristic name shows that the organic personality disorder can usually be caused by lesions in three brain areas of frontal lobe. Specifically, the symptoms of organic personality disorder can also be caused by traumatic brain injuries in orbitofrontal cortex, anterior cingulate cortex and dorsolateral prefrontal cortex. It is worth to be mentioned that organic personality disorder may also be caused by lesions in other circumscribed brain areas.

Personality disorders (PD) are a class of mental disorders characterized by enduring maladaptive patterns of behavior, cognition, and inner experience, exhibited across many contexts and deviating markedly from those accepted by the individual's culture. These patterns develop early, are inflexible, and are associated with significant distress or disability. The definitions may vary somewhat, according to source. Official criteria for diagnosing personality disorders are listed in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) and the of the "International Classification of Diseases" (ICD). The DSM-5 lists personality disorders in the same way as other mental disorders, rather than on a separate 'axis', as previously.

Personality, defined psychologically, is the set of enduring behavioral and mental traits that distinguish between individual humans. Hence, personality disorders are defined by experiences and behaviors that differ from societal norms and expectations. Those diagnosed with a personality disorder may experience difficulties in cognition, emotiveness, interpersonal functioning, or impulse control. In general, personality disorders are diagnosed in 40–60% of psychiatric patients, making them the most frequent of psychiatric diagnoses.

Personality disorders are characterized by an enduring collection of behavioral patterns often associated with considerable personal, social, and occupational disruption. Personality disorders are also inflexible and pervasive across many situations, largely due to the fact that such behavior may be ego-syntonic (i.e. the patterns are consistent with the ego integrity of the individual) and are therefore perceived to be appropriate by that individual. This behavior can result in maladaptive coping skills and may lead to personal problems that induce extreme anxiety, distress, or depression. These behaviour patterns are typically recognized in adolescence, the beginning of adulthood or sometimes even childhood and often have a pervasive negative impact on the quality of life.

Many issues occur with classifying a personality disorder. Because the theory and diagnosis of personality disorders occur within prevailing cultural expectations, their validity is contested by some experts on the basis of inevitable subjectivity. They argue that the theory and diagnosis of personality disorders are based strictly on social, or even sociopolitical and economic considerations.