Attention-deficit/hyperactivity disorder (ADHD) consists of several subtypes:

• Primarily inattentive presentation
• Primarily hyperactive-impulsive presentation.
• Combined presentation.

Children younger than 17 years need six symptoms to receive a diagnosis whereas children older than 17 years only need five symptoms. Intellectual disability (1), communication disorders (2), autism spectrum disorders (3), attention-deficit/hyperactivity disorder (4), specific learning disorder (5) and motor disorders (6) are included in the neurodevelopmental disorder section of the DSM-5.

There are several symptoms for the inattentive presentation:

• Careless attention to details.
• Problems sustaining attention over time.
• The child does not appear to listen.
• There is poor follow-through (e.g. schoolwork; homework; chores).
• The child is poorly organized.
• There is a poor ability to sustain mental attention (e.g. independent work at school).
• The child loses necessary materials (e.g. assignment sheets).
• The child is easily distracted.
• The child is forgetful.

To be diagnosed with this subtype, a child must show six out of nine symptoms (1), the symptoms are pervasive across two or more settings (2), they interfere with performance (3) and they have been evident prior to 12 years of age (4). The disorder is classified as mild, moderate or severe depending on the number of symptoms and the impairment.

Children with the inattentive presentation are often undiagnosed and misunderstood. These children may be characterized by a sluggish information processing style (i.e. slow to process information) and there may be problems with focused or selective attention. They are unable to filter essential from non-essential details. The lack of attention to detail results from information overload and the inability to selectively limit the focus of attention. The inattention is often misinterpreted as a lack of motivation. They have a poor performance on tests because of their poor attention and their poor concept of time and time management.

There are several symptoms for the hyperactive-impulsive presentation:

• The child demonstrated fidgety or squirmy behaviour.
• The child has problems remaining seated.
• The child shows excessive motion.
• The child has problems engaging in quiet play.
• The child is constantly on the go.
• The child shows incessant talking.

There are also several impulsivity symptoms:

• The child blurts out answers or comments.
• The child is impatient and has problems with turn taking.
• The child is intrusive to others.

Children with the hyperactive-impulsive presentation experience academic problems because of their impulsive nature. They emphasize speed over accuracy and approach tasks incorrectly because they do not wait for all the instructions. They are at social risk because their inability to wait for their turn can make them unpopular. Children with ADHD often have poor social skills and have difficulties making and maintaining friendships. They often gravitate towards other rule-breaking children and this can lead to other behavioural problems.

Children with the combined presentation must meet criteria for both the hyperactive-impulsive presentation and the inattentive presentation.

The earliest age of diagnosis is around the age of 3 though symptoms of inattention most likely only manifest themselves later. A difficult temperament (1), poor sleep patterns (2), excessive activity (3), irritability (4) and a difficulty soothing the child when they are upset (5) are precursors (i.e. risk factors) for developing ADHD in infancy.

During toddlerhood, the child may demonstrate higher levels of underregulated behaviours. Lack of self-control may persist during the transition to preschool. Children are more demanding (1), stressful (2) and problematic (3) during preschool, especially during unsupervised activities. The nature of the academic difficulties depend on how ADHD symptoms are manifested (e.g. inattention or impulsivity).

At least half of the children diagnosed with ADHD will continue to meet the criteria throughout adolescence. During this period, the emphasis on independent study skills (e.g. high school) puts these children at risk of significant academic difficulties. ADHD puts these adolescents at risk of internalizing problems as poor academic outcomes and social problems are a risk factor for this. There is more reckless behaviour in adolescence as well (e.g. substance use).

The prevalence of ADHD in school-aged children ranges from 3% to 7%. 90% of the children who receive a diagnosis have the hyperactivity-impulsivity subtype but this may be because of the large portion of children with the inattentive subtype that remain undiagnosed. Females may be more impaired in areas of psychosocial functioning. Females are also more likely to have the inattentive subtype of ADHD.

There is a high comorbidity between ADHD and other disorders with 66% of the elementary school children receiving another diagnosis as well. ADHD may be best understood within the context of the different developmental pathways that may result based on the comorbid features.

There is a comorbidity of 16% to 21% for ADHD and specific learning disorders (SLDs). This comorbidity is 70% for depression and 90% for younger and 30% of adolescents for bipolar disorder. The comorbidity is 35-60% for ODD and 50% for CD.

Irritability is common in ADHD (1), depression (2) and bipolar disorder (3). Irritable behaviours include problems concentrating (1), short attention span (2), restlessness (3), agitation (4) and impulsive responses (5). Symptoms of bipolar disorder and depression may be easily mistaken for ADHD. Children with bipolar disorder demonstrate rapid shifts of mood compared to lengthy moods for adults. This makes a differential diagnosis very difficult.

Children with ADHD and comorbid externalizing problems (e.g. ODD; CD) have worse outcomes compared to children with ADHD alone. There may be a socially disabled subtype for children with ADHD symptoms and a discrepancy between social skills and cognitive ability. This is associated with substance abuse (1), family problems (2), anxiety (3), mood problems (4) and conduct problems (5).

There are four biological features of ADHD:

1. Brain structure
   There is less activity in the frontal brain regions (i.e. executive functioning) and more activity in the cingulate gyrus (i.e. focusing of attention). Working memory (1), sense of time (2) and sustained effort (3) are areas of executive functioning which may be impaired for ADHD.
2. Genetic transmission
   About half of the children with ADHD have a parent with ADHD and 75% of the aetiology may be contributed to genetic factors.
3. Neurotransmitters
   There may be low catecholamines (e.g. dopamine; epinephrine; norepinephrine) in children with ADHD. This is associated with attention and motor activity.
4. Neurocognitive processing
   There may be a dysfunction in executive functioning which contributes to ADHD. Executive functioning include initiation or inhibition (1), flexibility in shifting focus (2), monitoring (3), evaluating (4) and adapting strategies (5). It is also involved in the management and control of other regulatory functions (e.g. behavioural and emotional control; self-regulation; motivation; persistence of effort).

The altered perception of time in ADHD is associated with reductions of dopamine in the basal ganglia. This may be accountable for the poor time management in ADHD. The poor time management may also be the result of dysfunction in the parietal lobe. Medication for ADHD (e.g. Ritalin) increases the number of catecholamines in the brain.

Barkley’s model of ADHD centres around behavioural inhibition. It states that a child’s degree of success in behavioural inhibition is central to determining the outcome of working memory (1), self-regulation (2), internalization of speech (3) and reconstitution (4). These are all four central executive functioning tasks. Working memory permits tasks of sequential ordering and planning. Self-regulation modulates activity to initiate goal-directed behaviours and sustain effort. Internalization of speech slows down reactivity and promotes inner reflection. Reconstitution analyses and synthesises information. According to the model, deficits in behavioural inhibition result in poor problem-solving strategies based on an inability to integrate and coordinate information generated by the four central processes. This may explain the hyperattentive-impulsive presentation.

Selective attention refers to the inability to filter essential from non-essential details. According to this model, children with the hyperactive-impulsive variant have problems with sustained attention and not with selective attention. Barkley states that sustained attention consists of attention for effortful tasks and contingency-based attention (i.e. self-rewarding attention). Children may have less problems with contingency-based attention in novel situations giving the false idea that these children are focused when they want to.

For the assessment of ADHD, a semi-structured interview is useful and it is important to use multiple informants (e.g. parents; teachers). It is also important to obtain information concerning other areas of potential diagnostic concern (e.g. depression). Cognitive assessment may be useful to evaluate processing deficits in areas of cognitive efficiency, processing speed or working memory as this is imperative for academic achievement and poor academic achievement is associated with ADHD.

The ASEBA and CRS-3 behavioural rating scales provide information form both a dimensional and categorical approach to the classification of ADHD. The BASC-2 provides an index of functioning based on a dimensional classification system. There are also scales to evaluate executive functioning. Scales for executive functioning include organization (1), attention (20, sustained effort (3), modulating emotions (4), working memory (5) and monitoring or evaluation (6).

The treatment alternatives for ADHD depend on the comorbid features (1), symptoms (2) and the nature and extent of functional impairment (3). The interventions can be applied at school, at home or in interactions with peers. Stimulant medication is more effective than behavioural therapy in alleviating core symptoms of the disorder. However, there are no long-term differences. Children with the combined ADHD subtype had the worst outcomes in adolescence.

There are three classes of stimulants for ADHD.

• Amphetamines (e.g. Adderall).
• Methylphenidates (e.g. Ritalin)
• Pemoline (e.g. Cylert).

Anxious children with ADHD may benefit equally well from behaviour therapy compared to medication. Stimulant medication may lead to a lack of height gain. Parent training can improve parenting skills, reduce parental stress, reduce core symptoms of ADHD and reduce non-compliance. Interventions often involve non-contingency management programmes base on the information provided from a functional behavioural assessment. It may be useful to combine parent training with teacher consultation to generalize behaviours from the home to school environment.