Theories of ADHD
cortical-striatal circuit has been proposed to explain the heterogeneous nature
of ADHD.6 A decrease in the volume of the right anterior frontal
region and loss of normal left to right striatal asymmetries have been shown on
MRI studies. These findings support the involvement of the frontal lobes and
striatal connections in the pathophysiology of ADHD. A temporal lobe arachnoids
cyst-ADHD syndrome has also been described in a patient with coincidental
learning and language disabilities.7
factors account for approximately 80% of the etiology of ADHD.8
twin and adoption studies support the theory that ADHD is a highly heritable
disorder, with the majority of patients having a first or second degree relative
with a history of ADHD or learning disorder.9
Pregnancy and birth related risk factors include maternal smoking, exanthema,
maternal anemia, breech delivery, prematurity, low birth weight,
hypoxic-ischaemic encephalopathy, small head circumference, cocaine/alcohol
exposure and iodine/thyroid deficiency.
the factors implicated during pregnancy, maternal smoking has attracted the
greatest attention in recent literature.
Childhood illnesses associated with occurrence of ADHD include viral infections,
meningitis, encephalitis, otitis media, anaemia, cardiac disease, thyroid
disease, epilepsy, autoimmune and metabolic disorders. Other causative factors
include head injury involving the frontal lobes, toxins/drugs and nutritional
disorders (eg food additives, food allergies, sucrose, gluten sensitivity and
fatty acid/ iron deficiencies).
Brain Insult theory:
hypothesised brain damage may potentially be associated with circulatory, toxic,
metabolic, mechanical or physical injuries to the brain during infancy caused by
infection, inflammation and trauma. Children with ADHD exhibit non focal (soft)
neurological signs at higher rates than those in the general population.
peripheral sympathetic system is of more importance in ADHD. Thus a dysfunction
in the peripheral system which causes norepinephrine to accumulate peripherally
could potentially feedback to the central system and set the locus ceruleus at a
human brain usually undergoes major growth spurts at several ages: 3 to 10
months, 2 to 4 years, 6 to 8 years, 10 to 12 years and 14 to 16 years. Some
children have a maturational delay in the sequence and manifest symptoms of ADHD
that appear to normalize by 5 years of age. A physiological finding is a number
of electroencephalographic correlates which normalize by the age of 5 years in
few cases. For instance, increased beta band percentage or decreased delta band
percentage is associated with increased arousal.
using positron emission tomography have found lower cerebral blood flow and
metabolic rates in the frontal lobe areas of children with ADHD than controls.
PET scans have also shown that adolescent females with the disorder have
globally lower glucose metabolism than both normal control females and males
with the disorder.
Prolonged emotional deprivation may explain the overactivity and poor attention
spans in ADHD such as in children who are placed in institutions. These children
tend to normalize as the deprivational factors are removed.
Stressful psychic events, disruption of family equilibrium and other anxiety
inducing factors contribute to the initiation and perpetuation of ADHD.
Predisposing factors include child’s temperament, genetic familial factors and
the demands of society to adhere to a routinized way of behaving and performing.
Clinical Features of ADHD
Predominantly inattentive types include:
distracted, missing details, forgetting things and frequently switching from one
activity to the other
focusing on one task
with a task after only few minutes
in organising and completing a task or having difficulty in learning something
new and often losing things (eg pencils, toys, assignments)
Not seeming to
listen when spoken to
in processing information as quickly and accurately as others
hyperactive-impulsive type symptoms include:
10. Fidgeting and squirming in their
11. Talking persistently
12. Being constantly in motion, touching
or playing with anything and everything in sight
13. Having difficulty in sitting still
during dinner, school and story time
14. Having difficulty in doing quiet
tasks or activities
15. Manifestations of impulsivity are
16. Being very impatient
17. Blurting out inappropriate comments,
showing their emotions without restraint and to act without regard for
18. Having difficulty waiting for things
they want or waiting for their turns in games
19. A 2009 study found that children with
ADHD move around excessively because it helps them stay alert enough to complete
Differential diagnosis of ADHD
may accompany other disorders such as anxiety or depression. Such combinations
can greatly complicate diagnosis and treatment. Where a mood disorder
complicates ADHD, it would be prudent to treat the mood disorder first but
parents of children who have ADHD often wish to have the ADHD treated first
because the response to treatment is quicker.11
the diagnosis of ADHD, a number of other possible medical and psychological
conditions must be excluded.
Hearing or vision
& Child abuse 12
is substantial empirical evidence from a neuroanatomic standpoint to suggest
that there is considerable overlap in the central nervous system centres that
regulate sleep and those that regulate attention/arousal.13 There are
multilevel and bidirectional relationships among sleep, neurobehavioural
functioning and the clinical syndrome of ADHD.14
Behavioural manifestations of sleepiness in children range from the classic ones
(yawning, rubbing eyes) to externalising behaviours (impulsivity, hyperactivity,
aggressiveness), to mood liability and inattentiveness.14,15
Children with ADHD should be regularly and systematically assessed for sleep
Management of ADHD
Combined medical management and behavioural treatment is the most effective ADHD
management strategy, followed by medication alone, and then behavioural therapy.
most common stimulant medications are methylphenidate (Ritalin),
dextroamphetamine (Dexedrine) and mixed amphetamine salts(Adderall). Atomoxetine
(Strattera) is currently the only non-stimulant drug approved for the treatment
of ADHD. Stimulant medication is an effective treatment for Adult ADHD although
the response rate may be lower for adults than children.17
Stimulants used to treat ADHD raise the extracellular concentrations of the
neurotransmitters dopamine and norepinephrine which causes an increase in
neurotransmission. The therapeutic benefits are due to the noradrenergic effects
at the locus coeruleus and the prefrontal cortex and the dopaminergic effects at
the nucleus accumbens.18
metaanalysis of clinical trials found that about 70% of children improve after
being treated with stimulants in short term but this conclusion may be biased
due to the high number of low quality clinical trials in the literature. There
have been no randomized placebo controlled clinical trials investigating the
long term effectiveness of methylphenidate beyond 4 weeks. Thus, the long term
effectiveness of methylphenidate has not been scientifically demonstrated.
Serious concerns of publication bias regarding the use of methylphenidate for
ADHD has also been noted.18
rates of schizophrenia and bipolar mood disorders as well as increased severity
of these disorders occur in individuals with a past history of stimulant use for
ADHD in childhood.19
Although under medical supervision, stimulant medications are considered safe,
the use of stimulant medications for the treatment of ADHD has generated
controversy because of undesirable side effects, uncertain long term effects and
social and ethical issues regarding their use and dispensation.20 The
United States FDA has added black box warning to some ADHD medications while the
American Heart Association and the American Academy of Paediatrics feel that it
is prudent to carefully assess children for heart conditions before treating
them with stimulant medications.
are a variety of psychotherapeutic approaches employed by psychologists and
psychiatrists: the one used depends on the patient and patient’s symptoms. The
approaches include psychotherapy, CBT, support groups, parent-training,
meditation and social skills training. If psychotherapy fails to bring
improvement, medications can be considered as an add-on or alternative.21
Improving the surrounding home and school environment can improve the behaviour
of children with ADHD.22
different educational interventions for the parents jointly called Parent
Management Training Techniques include operant conditioning: a consistent
application of rewards for meeting goals and good behaviour (positive
reinforcement) and punishments such as time outs or revocation for failing to
meet goals or poor behaviour.22Classroom management is similar to
parent management training. Strategies include increased structuring of
classroom activities, daily feedback and token economy.22
Working memory training
the problems shown by children with ADHD can be traced back to deficits in
working memory (or short term memory). By training and improving this memory,
some of the other symptoms may decrease as well. In a study by Klingberg et al.,
a computerised training program has shown good results in working memory, even
if the generated effect to behavioural symptoms was not as clear.
children and adolescents with ADHD, paediatric massage therapy has been found to
improve mood and increase on task behaviours while reducing anxiety and
psychologists feel that cutting down on the time spent on television, video
games or violent games, or violent media can help some children. One study
indicated a correlation between excessive TV time and a child with higher rates
of ADHD symptoms.25 Some psychologists feel Art therapy may be one of
the most effective therapies to help children to concentrate, slow down and
therapies that have been effective for some have been positive changes in diet,
such as low sugar, low additives and no caffeine. Children, who spend time
outdoors in natural settings (dubbed Green Therapy) such as parks, seem to
display fewer symptoms of ADHD.
supplements (seal,fish or krill oil) may reduce ADHD symptoms for a subgroup of
children and adolescents with ADHD characterised by inattention and associated
neurodevelopmental disorders.26 A meta-analysis has found that
dietary elimination of artificial food colouring and preservatives provides a
statistically significant benefit in children with ADHD.27 Other more
recent studies agree with these conclusions.28
diagnostic criteria need to be established for children, adolescent and adult
regarding the long term effects of the methods of treatment that have been in
use for several decades need to be established, as well as the long term
outcomes of children who have not been treated.
medications which are safer and more effective need to be developed for ADHD
Studies in areas
of prevention/early intervention that target known risk factors need to be
evaluation for rapidly evolving technology of brain imaging techniques as a
possible tool in the diagnosis and subsequent management of ADHD.
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