Attention Deficit Hyperactivity Disorder (ADHD)

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Introduction

Hyperactivity, impulsivity, and inattention generally constitute a specific spectrum of the disorder known as Attention Deficit Hyperactivity Disorder (ADHD).

Epidemiology 

  • School-age children are prone to develop ADHD with a prevalence of 3- 9 %. 
  • The male to female ratio is 3: 1.

Risk factors 

Certain factors are seemed to be associated with this disorder. 

They are – 

  • Premature birth or low birth weight
  • Maternal alcohol  intake or smoking during pregnancy
  • Close family history of ADHD
  • History of traumatic brain injury
  • Lead exposure
  • Psychosocial adversity
  • Family conflict
  • Neurofibromatosis type 1

Pathophysiology

  • Studies failed to find any certain gene locus for the disorder but could postulate the differences of the brain both at the structural and molecular levels with normal children.

  • Imaging studies revealed frontal and parietal cortex, basal ganglia, corpus callosum, and cerebellum are the responsible regions contributing to this particular disease. Children with ADHD tend to have a reduction in brain volume(marked in the prefrontal cortex)  along with abnormal pathways noted between the prefrontal cortex and corpus striatum.

  • Dopaminergic pathways seem to be less active in the ADHD group (Stimulant medications are used to increase dopamine level)
ADHD Symptoms

Diagnostic criteria

According to DSM 5 at least 6 of the following symptoms should  be present for at least 6 months to a level that is maladaptive and irrelevant with developmental level:

  1. Rapidly moving or tapping fingers or feet, squirming in the seat.
  2. Leaving sit when sitting is expected for example in a classroom.
  3. Running about or climbing excessively (in adolescents it may be manifested by a subjective feeling of restlessness).
  4. Difficulty engaging in leisure activities quietly.
  5. Uncomfortable being still for extended periods of time.
  6. Excessive talking.
  7. Blurting out answers before the questions have been completed.
  8. Difficulty waiting in lines or awaiting turn in games in group situations.
  9. Interrupting or intruding on others

Clinical presentation

No specific physical findings are strongly associated with ADHD.

Mental status examination depicts the following-

  • Appearance – Fidgety and cannot sit or standstill.
  • Mood – Usually appropriate but may be elevated. Mood disorder is not an outcome but a frequent association.
  • Speech and thought process – Speech is of normal rate but usually is louder due to impulsivity. Thought processes are short term goal-oriented and reflect difficulty staying on a particular topic or task.
  • Hallucinations and delusions – Absent.
  • Thought content – Normal with no evidence of suicidal/homicidal or psychotic symptoms
  • Cognition – Patients face difficulty in mathematical calculation. Short term or recent memory may be affected but orientation, remote memory, and abstraction are not affected.

Differential diagnosis

  1. Conduct disorder
  2. Oppositional defiant disorder

Both are very often overlapping with ADHD

  1. Mood disorder

Associated conditions

A number of disorders are linked to ADHD – 

  • Oppositional defiant disorder (50%)
  • Conduct disorder (20%)
  • Learning disabilities 
  • Tourette’s syndrome
  • Mood disorder
  • Anxiety disorder
  • Obsessive-compulsive disorder
  • Substance misuse
  • Sleep disorders

Treatment

1. Behavioral interventions are at first recommended which is mediated by parent training or education program. Cognitive behavior therapy or social skills training is also advised.

2. If there is a severe impairment to hamper daily activities and learning, medication can be commenced. 4 main drugs of choice are –

  1. Methylphenidate –  A dopamine reuptake inhibitor. Acts by blocking both dopamine transporter and norepinephrine transporter centrally. The end result is increased concentration of dopamine and norepinephrine in the synaptic cleft. It is generally well tolerated. But it may affect sleep and appetite. There is also a risk of raised Blood pressure and increased weight. So patients on Methylphenidate regimen should be reviewed specifically on each appointment.
  2. Atomoxetine – Second-line drug. Patients who are being hypertensive, having sleep or appetite difficulties, having comorbid tic disorder are switched over to Atomexitine. It primarily acts over the norepinephrine pathway. However, it has been associated with liver problems and suicidal thoughts.
  3. Amphetamines – when above mentioned 2 drugs were not tolerated amphetamine is prescribed which influences the release and the reuptake of noradrenaline and dopamine from central neurons.
  4. Clonidine – If all of them were poorly tolerated or the patient having associated tic disorder Clonidine, a centrally acting alpha 2 adrenergic agonist may be used.

Prevention

  • Avoid any activity that may cause poor pregnancy outcomes.
  • Protect your child from toxic chemicals or pollutants.
  • Limit the electronic device uses by your child. 

Long term outcome of ADHD

  • Some children (35% to 65%) continue to have symptoms throughout adulthood.
  • The rates of persistence of symptoms between males and females were similar.
  • Around one-third of the child with ADHD drop out of school.
  • A person with ADHD is eleven times more likely to be unemployed compared to the general population.
  • The earning potential of ADHD patients is significantly less than general population.
  • ADHD patients have 13% less life expectancy than the general population. 
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