Mental Disorders in Infancy, Childhood, Adolescence


Statistics on mental disorders show that they tend to prevail in infants, children, and adolescents. More than 2.5 million children in the USA suffer from different kinds of mental disorders and more than 13% are in the risk group (Paul, 2007). Disorders in children and adults are not clearly differentiated as those appearing at a mature age usually have their roots in childhood experiences. Besides, a lot of mental disorders are not curable and the symptoms continue into adulthood. Despite such an unclear distinction, the Diagnostic and Statistical Manual of Mental Disorders–IV (DSM-IV) identified a specific diagnostic category of disorders that are mostly discovered in infancy, childhood, and adolescence. Despite the fact that DSM-IV no longer uses this classification, the disorders that have been previously included in it, continue to be analyzed in a lot of studies on the topic (Mash & Barkley, 2014). The paper at hand is going to provide an overview of some of the most commonly encountered mental disorders diagnosed in infants, children, and adolescents. Since the research is scanning, it is not meant to be used in diagnostics.

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Mental disorders of any kind are typically diagnosed at an early age and continue to present a problem to the patient unless they are not treated in due time. Since there are many types of disorders, their symptoms vary drastically but generally include learning disabilities and slow development. DSM IV identifies ten major categories of disorders (Paus, Keshavan, & Giedd, 2008).

Intellectual disabilities

Intellectual disabilities signify poor mental activity that manifests itself in low IQ test scores. According to DSM-IV, there are five types of intellectual disabilities (Zahn-Waxler, Shirtcliff, & Marceau, 2008):

  1. Mild intellectual disability. This type is characterized by rather slow intellectual development, which does not eliminate the possibility to learn in normal settings. It usually appears in preschool years, The level of IQ is app. 50-70.
  2. Moderate intellectual disability. The second type refers to low test scores and a lower level of IQ (app.35-55).
  3. Severe intellectual disability. This level is given to the patients that have serious learning problems. The level of IQ is 20-40.
  4. Profound intellectual disability. This is the most severe level of retardation presupposing that the individual is not self-sufficient. The level of IQ is under 20.
  5. Unspecified Intellectual disability. This diagnosis is given when the patient cannot be tested because of being seriously impaired.

The diagnostic criteria include (Kieling et al., 2011):

  • the level of IQ below 70;
  • inability to meet various standards identified for the patient’s age;
  • inability to take care of oneself;
  • lack of social, communicative, and academic skills;
  • the emergence of symptoms before 18.

All the types of intellectual disabilities can appear due to the inborn malfunction of the brain (which can be caused by a pre-natal trauma) as well as due to environmental influence.

The following pre-natal causes can be singled out (Kieling et al., 2011):

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  • congenital infections;
  • maternal fever at an early stage of pregnancy;
  • alcohol abuse;
  • maternal phenylketonuria;
  • health complications at early stages of development;
  • single-gene disorders (neurofibromatosis, tuberous sclerosis, etc.).

A patient suffering from any kind of intellectual disability usually develops slower than other children of the same age. He/she has trouble learning to walk, feed himself/herself, memorize things, and talk. Besides, such children are usually apathetic, unable to concentrate, do not show any interest in learning, cannot meet the educational standards, and cope with intellectually challenging tasks. In the most severe cases of mental retardation, children may have problems with eye-sight or hearing and be limited in their ability to move (Beesdo, Knappe, & Pine, 2009).

Mostly, intellectual disability is incurable, however, there exist many different therapies that help patients lead a normal life and be self-sufficient. Besides, there are special educational opportunities for mentally retarded students that allow them to have an individual learning program (Beesdo et al., 2009).

Learning Disabilities

Learning disabilities are disorders that complicate the process of learning. In DSM-IV classification, there are six types of such disabilities (Zahn-Waxler et al., 2008):

  1. Reading disorder. This disorder hinders reading comprehension and speed. In most cases, patients are unable to study successfully as they cannot understand written tasks correctly.
  2. Dyslexia. It can be referred to as reading disorders but is often placed in a separate group as people affected by dyslexia have a particular problem of switching letters in words, which makes it difficult for them to memorize correct sequences of letters.
  3. Spelling disorder. This is sometimes connected to writing disorder or dysgraphia but is characterized only by the inability to spell with normal ability to express one’s thoughts in writing.
  4. Mathematics disorder. As it is evident from the name, this disability is connected with operations with numbers.
  5. Disorder of written expression. Dysgraphia complicates the process of writing and in the most severe cases makes it impossible to express one’s thoughts in writing.
  6. Unspecified learning disorder. In some cases, children may have a mixture of symptoms related to different disorders. In general, these symptoms do not meet the criteria of any of the cases enumerated above. The disorder is marked as unspecified.

Learning disorders are usually connected with certain disruptions of the work of the nervous system. The structure of the brain may be impaired genetically or because of a trauma or exposure to toxins. Also, the functioning of its chemicals may be distorted. As a result of such physiological problems, the patient cannot receive and process information.

Learning disabilities usually manifest themselves in (Zahn-Waxler et al., 2008):

  • poor reading or total inability to perceive written texts;
  • inability to learn the letters and memorize spelling rules;
  • the trouble with memorizing and following given directions;
  • inability to build logical sequences (whether a numerical, letter or word chains);
  • inability to understand the meanings of written words;
  • inability to express one’s thoughts logically;
  • misinterpretation of symbolical expressions;
  • inability to predict the continuation of a text, numerical sequence, or the next step of a task.

Like intellectual disabilities, learning disorders cannot be cured completely despite the fact that there exist a lot of services and programs helping children to integrate into a normal learning environment so that these disorders do not impede the learning process. Speech and language therapy is especially helpful to teach children the ways to receive and process the incoming data (Zahn-Waxler et al., 2008).

Motor Skills Disorder

This disability is also known under the commonly accepted name of dyspraxia. It impairs children’s capacity to move and perform certain tasks of different complexity (depending on the stage of the disorder). Sometimes, motor skills disorder may go together with hypotonia or hypertonia. DSM-IV identifies only one type of disability – developmental coordination disorder. It is characterized by children’s inability to develop normal coordination. The symptoms may appear right after birth or later in infancy (Mash & Barkley, 2014).

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The etiology of motor skills disorder is rather vague. It is believed to be caused by both genetic and environmental factors and is often linked to distortions of physiological development. At an early age, babies with motor skills disorder may suffer from either hypertonia or hypotonia. Later, they may be unable to feed themselves and have trouble with standing, sitting, or walking. Such children are usually clumsy in their movements and cannot perform complex activities like dancing or drawing. Motor skills may be improved with the help of occupational and physical therapies (sensory therapy, kinesthetic training, etc.) (Mash & Barkley, 2014).

Communication Disorders

These disorders affect oral motor skills or may refer to other problems connected with entering the communicative process. According to DSM-IV, there are five types of communication disorders (Paul, 2007):

  1. Expressive language disorder. The specific feature of this condition is that children suffering from it usually have a normal understanding of what they are told but have difficulties to express their own thoughts.
  2. Mixed receptive-expressive language disorder. This type is characterized by both problems with understanding and expression.
  3. Phonological disorder. Children having this disorder cannot produce sounds and connect them in words.
  4. Acquired aphasia with epilepsy (Landau-Keffner syndrome). The syndrome not only impairs communication but also provokes seizures.
  5. Stuttering. Children who stutter cannot pronounce words correctly and smoothly and have to repeat sounds.
  6. Unspecified communication disorder. When features of several disorders are present, the patient is diagnosed with an unspecified communication disorder.

Communication disorders fall into biological, developmental, and environmental. Children affected by them usually have a very poor vocabulary, which does not allow them to name even simple objects. They can neither utter nor perceive full sentences. When they grow up, they have trouble expressing and comprehending abstract notions. Communication skills can be developed in the course of language therapy that encourages children to establish connections and initiate communication (Paul, 2007).

Pervasive Developmental Disorders

Pervasive Developmental Disorders can hinder the development of many skills including socialization, communication, etc. Children having developmental disorders have trouble to understand how certain things function and what purpose they serve. These disorders fall into five subcategories (Kieling et al., 2011):

  1. Autistic disorder or autism. This type usually appears within first years of life and is characterized by social detachment and communication problems.
  2. Rett’s Disorder. The disorder affects the structure of the brain. As a result, children have small hands, feet, and head.
  3. Childhood disintegrative disorder. Children affected by this disorder develop normally for 3-5 years and then show symptoms of various disabilities.
  4. Asperger’s Disorder. This is a type of autism, which has the same symptoms but in milder form.
  5. Unspecified pervasive developmental disorder. The diagnosis is made when the patient has several disabilities that can be attributed to different types.

Pervasive developmental disorders appear for an unidentified reason. A lot of studies have been carried out to link these conditions to brain structure. The major symptoms are (Kieling et al., 2011):

  • failures connected with socialization;
  • difficulties with understanding both verbal and non-verbal information;
  • anger outbursts;
  • aggression;
  • peculiar games and interaction with toys and inanimate objects;
  • anxiety caused by the necessity to meet new people or go to new places.

Since the symptoms may vary significantly in each case, the treatment is individualized. It is generally aimed at developing social skills and eliminating erratic behaviors. Sometimes, medication and physical therapy are also required (Kieling et al., 2011).

Attention-Deficit and Disruptive Behaviour Disorders

Attention-Deficit and Disruptive Behaviour Disorders make a person unable to focus attention. The types are (Mash & Barkley, 2014):

  1. Attention-deficit hyperactivity disorder (ADHD). This condition may vary considerably but is generally connected with concentration problems.
  2. Conduct disorder. This type is connected with uncontrolled bad behavior.
  3. Oppositional defiant disorder. The condition is characterized by anger outbursts that signalize protest.
  4. Unspecified disruptive behavior disorder. The diagnosis is made when the symptoms cannot be attributed to any of the above-mentioned conditions.

Many studies connect these disorders with genetic factors claiming that affected children have thinner brain tissue responsible for concentration. When the tissue thickens, the symptoms disappear. However, other researchers have proven that such environmental factors as smoking or alcohol abuse during pregnancy can cause ADHD. The following symptoms can be identified (Mash & Barkley, 2014):

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  • trouble with socialization;
  • aggression and anger outbursts;
  • inability to concentrate for a long time;
  • difficultly with understanding and following instructions;
  • frustration;
  • poor performance at school.

Children suffering from attention-deficit and disruptive behavior disorders are treated with medications. Various programs may help them socialize and improve their marks at school. In some cases, the condition may disappear but in others, it continues into the adult life (Mash & Barkley, 2014).

Feeding and Eating Disorders of Infancy or Early Childhood

Such disorders are connected with eating inedible items and other eating problems. DSM-IV identifies 3 variations (Mash & Barkley, 2014):

  1. Pica. The condition is characterized by the tendency to eat inedible things even if they are harmful for health.
  2. Rumination Disorder. The disorder is chronic and is connected with regurgitation after meals.
  3. Feeding disorder of infancy or early childhood. The diagnosis is made when the disorder appears as a result of a medical problem.

Feeding disorders generally imply inability to eat normally (without any gastrointestinal reasons) that may result in weight loss or obesity. They may be caused by physiological (chemical disruption), developmental (lack of motor skills), environmental (unscheduled meals), relational (emotional trauma connected with relations with parents) or psychological (character peculiarities) factors. The disorders are easy to diagnose because of weight changes and aggression. The problem is treated through application of behavioral therapy (Mash & Barkley, 2014).

Tic Disorders

Tic disorders are manifested in abrupt movements and uncontrolled sounds. The types are (Beesdo et al., 2009):

  1. Tourette’s disorder. This disorder is characterized by both motor and vocalic tics.
  2. Chronic motor or vocal tic disorder. The condition is diagnosed when there is only one tic present.
  3. Transient tic disorder. The disorder is connected with uncontrolled repetitive movements.
  4. Unspecified tic disorder. Individuals with mixed symptoms are referred to this type.

The causes are unknown. Tic disorders may appear due to generic, chemical or environmental factors. Two thirds of such disorders have a genetic component. They are characterized by (Beesdo et al., 2009):

  • fists clenching;
  • fast eye blinking;
  • excessive movements;
  • uncontrolled noises;
  • kicking.

Tics may disappear when they are neglected by others. In some cases, medications may be used.

Elimination Disorders

These disorders are connected with the elimination of feces or urine (Mash & Barkley, 2014):

  1. Encopresis. The condition is found in children who are toilet trained but continue involuntary passage of stools.
  2. Enuresis. This refers to involuntary urination.

The first condition is caused by an unhealthy diet, stress or sedentary life style whereas the second one may appear due to genetic, physiological, and psychological factors. No other symptoms are found. However, sometimes there may appear abdominal pains and skin irritation. The problem may disappear when children grow up. Sometimes, behavioral therapy and medications are required (Mash & Barkley, 2014).

Other Disorders of Infancy, Childhood or Adolescence

There are some other disorders that may be diagnosed as an early age (Mash & Barkley, 2014):

  1. Separation anxiety disorder. The condition causes severe stress in children who miss places or people too much.
  2. Sibling rivalry disorder. The disorder is connected with unhealthy relationships with siblings.
  3. Selective mutism. Children with this disorder cannot communicate in unfamiliar situations.
  4. Reactive attachment disorder. The condition is connected with social interaction problems.
  5. Stereotypic movement disorder. Children suffering from it show non-functional motor behavior.


There are a lot of factors that may trigger the appearance of disorders in infancy, childhood, and adolescence. Most of these disabilities are genetic. However, some conditions may be aggravated by environmental factors. Some of them are connected with the inability of parents to provide proper care to their children. Most of the disorders involve problems with socialization, aggression, stress, behavior problems, and learning difficulties. Treatment usually involves not only the child but also his/her parents and teachers. Parents must stay in close contact with the affected child to help him/her overcome anxiety and accept therapies without resistance. It is usually impossible to cure these conditions completely but physical, behavioral, language, and other therapies coupled with medications may improve the situation significantly.


Beesdo, K., Knappe, S., & Pine, D. S. (2009). Anxiety and anxiety disorders in children and adolescents: developmental issues and implications for DSM-V. Psychiatric Clinics of North America, 32(3), 483-524.

Kieling, C., Baker-Henningham, H., Belfer, M., Conti, G., Ertem, I., Omigbodun, O.,… & Rahman, A. (2011). Child and adolescent mental health worldwide: evidence for action. The Lancet, 378(9801), 1515-1525.

Mash, E. J., & Barkley, R. A. (Eds.). (2014). Child psychopathology. New York, NY: Guilford Publications.

Paul, R. (2007). Language disorders from infancy through adolescence: Assessment & intervention. New York, NY: Elsevier Health Sciences.

Paus, T., Keshavan, M., & Giedd, J. N. (2008). Why do many psychiatric disorders emerge during adolescence?. Nature Reviews Neuroscience, 9(12), 947-957.

Zahn-Waxler, C., Shirtcliff, E. A., & Marceau, K. (2008). Disorders of childhood and adolescence: Gender and psychopathology. Annual Review of Clinical Psychology, 4, 275-303.

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