Attention-deficit/hyperactivity disorder (ADHD)

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Introduction: 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 Sex/Age Ratio: • 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. Epidemiology:  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. . Causes:  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 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. Environmental Factors Pregnancy and Delivery Complications These factors include: • Prenatal and delivery complications • Prenatal or perinatal brain injury • Prematurity • 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 Environmental Factors Others: • Exposure to Toxins • Mercury, manganese, lead • Polychlorinated bi-phenyls
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