Attention Deficit Hyperactivity Disorder is the most common disorder among children and may be diagnosed to adults too, where it is referred to as Adult Attention Defecit Disorder (AADD). Currently around 30% of children retain the disorder into adulthood. Stimulant and sometimes antidepressant medications can help treat the disorder.

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Down syndrome is a syndrome that causes slowed growth, abnormal facial features, and mental retardation. It is caused by an extra chromosome 21. Incidence of Down syndrome is estimated at 1 per 800 births, making it the most common chromosomal abnormality.

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Dyscalculia is a learning disability affecting a person's ability to understand and manipulate numbers. Like dyslexia, it can be caused by visual perception. Some even perceieve it to be a variation of dyslexia. Dyscalculia affects people across the whole IQ range, but means they have problems with mathematics, time, measurement, etc. The disability is not rare and many of those who have Dyslexia or Dyspraxia also have the disability. There is some evidence to indicate it may be hereditary.

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Dysgraphia is a difficulty for writing correctly despite how profiecient you can read. People with this disorder can write, but have trouble doing so with co-ordination. They can also lack basic spelling skills, say the wrong word when formulating a sentence and sometimes can have trouble tying their own shoes.

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Dyslexia is a neurological disorder with biochemical & genetic markers. It is a disability which a person reading and/or writing ability is lower than his or her grade level of intelligence. However, people may read and write perfectly and have dyslexia. They are diagnosed with the disorder when their problems can't be explained by a lack of intellectual ability, inadequate instruction or problems such as poor eyesight. Being as it is a complex mental process, it can have many potential causes. From a neurophysiological perspective, it can be diagnosed by closer inspection of the brain. It is associated with phonological problems.

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Dyspraxia is a development coordination disorder (DCD) more comon in males than females and affects anywhere from 8-10% of all children. It is believed to be due to immature neuron development. It can be present in people with autism spectrum disorder, dyslexia & dycalculia. It has two main elements:

Ideational Dyspraxia: Difficulty planning sequence of coordinated movements

Ideo-Motor Dyspraxia: Difficulty executing a plan.

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