Child development entails the biological, psychological and emotional changes that occur in human beings between birth and the end of adolescence, as the individual progresses from dependency to increasing autonomy. It is a continuous process with a predictable sequence, yet having a unique course for every child.
Child and adolescent psychiatry are relevant to all clinicians who treat either young people or their family members. Emotional, behavioral, and developmental problems are common among children of all ages in Child Development.
A recent UK prevalence study reported 10 per cent of children aged 5 to 15 years reached diagnostic criteria for a psychiatric disorder. To help these children and their families effectively requires knowledge of normal child development and of the behavioral disorders of this time of life, together with the skills needed to interview the child, assess the problem, and use basic forms of management. 
The following account summarizes points that are particularly relevant to the study of childhood emotional and behavioral disorders. It is important to remember that there are wide variations in the speed of development of healthy children.
The child learns about the basic attributes of common objects, spatial relationships.
By 3 months: They have developed a preference for humans over inanimate objects, and
In the next 4 months, start to distinguish between people and form specific attachments.
From about 7 months, most children can sit without support.
By about 8 months, the child shows signs of distress when separated from the mother, and in the presence of strangers.
By about 12–14 months, most can take a few steps unaided.
At a year, the child will cooperate with dressing, wave goodbye, and understand simple commands. They should also have a regular pattern of feeding and sleeping. The child forms a strong, secure emotional bond with their regular cares.
The child begins to walk, explores the environment, and learns that this exploration will be limited at times by the parents (e.g. to avoid danger). The parents demand more of the child as they encourage bowel and bladder training.
From 18 months, the child will show some interest in peers.
By 2 years will play alongside (but not with) them. They will be able to recognize themselves in a mirror, and start to understand symbols and make-believe play.
By the age of 20 months most children have learnt the words ‘dada’, ‘mama’, and three others. As speech and language comprehension increase, it becomes easier for the parents to understand their child’s wishes and feelings and to respond to them appropriately. 
Age of 2-5 Years:
The child can run, and learns to draw circles, crosses, and then triangles. In this period there is rapid development of language and intellectual functions and children ask many questions.
Attention span increases, motor skills are refined, and continence is achieved. Children become less self-centered and more sociable and they learn to share in the life of the family. During this period children are capable of vivid fantasy, expressed in imaginative games. Play helps children to learn how to relate to other children and adults, explore objects, and increase their motor skills. 
By 6 years, the child should be able to skip and hop, draw simple shapes, and know left from right. Speech is usually fluent, and they are able to dress themselves alone. Upon starting school, children learn about social relationships with other children and with adults other than the parents. Skills and knowledge increase. Ideas of right and wrong develop further at this age as the influence of school is added to that of the family. Children develop a feeling of self-worth, while learning that they are less successful in some activities than their peers are. 
Considerable changes—physical, psychosexual, and social—take place in adolescence and they are usually accompanied by some emotional turmoil. The individual has to come to terms with a new physical self, develop a sense of personal identity and a value system, meet school demands, establish vocational skills, adapt to emotional independence from their parents. In most this occurs relatively smoothly, but it can be a difficult time, and is frequently when psychiatric problems develop.
Among older adolescents rebellious behavior is common, especially during the last years of compulsory attendance at school. Other common problems include relationships, sexual difficulties, delinquent behaviour, excessive drinking of alcohol, and abuse of drugs and solvents. 
Child and adolescent Psychiatry Vs. Adult Psychiatry:
- Development is a dynamic process; children’s behaviour and emotions change with age and psychiatrists’ assessment and treatment need to reflect this.
- A child is not an isolated individual; they come in the midst of a family unit and social situation. It may not always be the child who has the greatest need for psychiatric attention.
- It is usually the parents who present with concern that there is a problem with their child, rather than the patient themselves identifying a difficulty.
- Children are smaller than and have different physiology from adults; therefore, appropriate medications must be prescribed.
- Children are dependent on others for all of their needs.
- Young people tend to have less choice about their home environment, school, activities, and friends than adults do.
- Children are highly receptive to changes in their environment. Therefore, many forms of treatment (behavior, art, play therapy) that use this have much greater importance.
- There are some conditions (e.g. enuresis) that the majority of children will ‘grow out of.
- Those less than 18 years of age are minors in the eyes of the law, and therefore others can make decisions for them.