Attention-deficit/hyperactivity disorder (ADHD) is defined as a behavioral disorder of childhood onset (by the age of 7 years) characterized by symptoms of inattentiveness and impulsivity/hyperactivity. Based on the type of symptoms that predominate, ADHD is classified as following:
Combined type: both inattention and hyperactivity/impulsivity symptoms are present
Predominantly inattentive subtype
Predominantly hyperactive/impulsive subtype
Not otherwise specified (NOS): individuals presenting with atypical features
• ADHD is a developmental disorder that requires an onset of symptoms before age 7 years. After childhood, symptoms may persist into adolescence and adulthood, or they may ameliorate or disappear.
• The percentages in each group are not well established, but at least an estimated 15-20% of children with ADHD maintain the full diagnosis into adulthood. As many as 65% of these children will have ADHD or some residual symptoms of ADHD as adults.
• The prevalence rate in adults has been estimated at 2-7%. The prevalence rate of ADHD in the adult general population is 4-5%.
• In children, ADHD is 3-5 times more common in boys than in girls. Some studies report an incidence ratio of as high as 5:1. The predominantly inattentive type of ADHD is found more commonly in girls than in boys.
• In adults, the sex ratio is closer to even.
Incidence in school-age children is estimated to be 3-7%.
ADHD prevalence varies by race and ethnicity, with Mexican children having consistently lower prevalence compared with other racial or ethnic groups.
Prevalence of ADHD increases to 10% for children with family incomes less than 100% of the poverty level and to 11% for those with family income from 100-199% of the poverty level.
As such no single etiology has been identified for ADHD. ADHD is a heterogeneous condition currently thought to result from a complex interaction between the psychosocial stressors, environmental factors, neuro-chemical/ neuro-anatomical factors, familial and genetic factors.
• Psychosocial stressors are not thought to cause ADHD
• ADHD symptom and co morbidity related to levels of stress and psychosocial adversity
• Higher levels of stress and psychosocial adversity in children with ADHD and co morbid anxiety or mood disorders than in children with ADHD alone.
• Children with ADHD and no co morbidities had levels of psychosocial stress no different than controls.
Pregnancy and Delivery Complications
These factors include:
• Prenatal and delivery complications
• Prenatal or perinatal brain injury
• Small for gestational age
• Low birth weight
The following factors have not been supported by research as having an association with development of ADHD.
• Allergic or toxic reactions to food additives
• Refined sugar
• Exposure to Toxins
• Mercury, manganese, lead
• Polychlorinated bi-phenyls