Achenbach has identified two factors in behavioural disorders:

1. Externalizing Factors
2. Internalizing Factors

These disorders must manifest before the age of 18. On the basis of these two factors he classified children's disorders into two categories:

• The externalizing disorders or undercontrolled emotions: Behaviours that are disruptive and often aggressive and aversive to others in the child's environment.

• The Internalizing disorders or over-controlled emotions: Those conditions where the child experiences depression, anxiety, and discomfort that may not be evident to others.

1. Externalising Disorders:

(a) Attention-deficit Hyperactivity Disorder (ADHD).

(b) Oppositional Defiant Disorder (ODD).

(c) Conduct Disorder.

(a) Attention-deficit Hyperactivity Disorder (ADHD):

The two main features of ADHD are:

(i) Inattention

(ii) Hyperactivity-impulsivity.

Inattention:

• Children who are inattentive find it difficult to sustain mental effort during work or play.

• They have a hard time keeping their minds on any one thing or in following instructions.

Common complaints are that

• The child does not listen, cannot concentrate, does not follow instructions, is disorganized, easily distracted forgetful, does not finish as signments, and is quick to lose interest in boring activities.

• Children who are impulsive, unable to control their immediate reactions or to think before they act.

• They find it difficult to wait or take turns, have difficulty resisting immediate temptations or delaying gratification.

• Minor mishaps such as knocking things are common whereas more serious accidents and injuries can also occur.

• Hyperactivity also takes many forms. Children with ADHD are in constant notion. Sitting still for some time through a lesson is impossible for them. The child may fidget, squirm, climb and run around the room aimlessly.

• Parents and teachers describe them as 'driven by a motor', always on the go, and talk a lot.

• Boys are four times more prone for this diagnosis than girls.

(b) Children with Oppositional Defiant Disorder (ODD):

• Age-inappropriate amounts of stubbornness,

• Irritable,

• Defiant, disobedient, and

• Behave in a hostile manner.

Unlike ADHD, the rates of ODD in boys and girls are not very different.

(c) Conduct Disorder and Antisocial Behaviour refer to age-inappropriate actions and attitudes that violate family expectation, societal norms, and the personal or property rights of other.

The behaviours typical of conduct disorder include:

• Aggressive actions that cause or threaten harm to people or animals,

• Non-aggressive conduct that causes property damage,

• Major dishonesty,

• Theft and

• Serious rule violations.

Children show many different types of aggressive behaviour, as—1

• Verbal aggression (i.e., name-calling, swearing),

• Physical aggression (i.e., hitting, fighting),

• Hostile aggression (i.e., directed at inflicting injury to others),

• Proactive aggression (i.e., dominating and bullying others without provocation).

2. Internalizing disorders

(a) Separation Anxiety Disorder (SAD) (b) Depression

(a) Separation anxiety disorder is an internalizing disorder unique to children.

Its most prominent symptom is—

• Excessive anxiety or even panic experienced by children at being separated from their parents.

• Have difficulty being in a room by themselves, going to school alone, are fearful of entering new situations, and cling to and shadow their parents' every move.

• To avoid separation, children with SAD may fuss, scream, throw severe tantrums, or make suicidal gestures.

(b) Depression:

• An infant may show sadness by being passive and unresponsive; a preschooler may appear withdrawn and inhibited; a school-age child may be argumentative and combative; and a teenager may express feelings of guilt and hopelessness.