Mild intellectual disability

In early childhood, children with mild ID may be developmentally indistinguishable from typically developing children. Many people with mild ID have an IQ between 55 and 70; however, the Diagnostic and Statistical Manual of Mental Disorders (DSM) states that diagnosis of a level of intellectual disability should be determined based on level of adaptive functioning, not IQ test scores. ==Causes==

A specific biological cause is less likely to be found in cases of mild intellectual disability than for more severe forms of intellectual disability. About 21% of cases of mild ID are caused by known genetic microdeletions and duplications. In comparison to more severe forms of ID, which are relatively stable in prevalence across populations, the incidence of mild ID varies widely based on external environmental factors, such as access to education and healthcare. Mild ID is also more likely to be nonsyndromic than more severe forms of ID. . Down syndrome is commonly comorbid with mild ID. There are also many syndromic causes of mild ID. About 20-50% of adults with Down syndrome (DS) have mild intellectual disability. A lack of comorbid epilepsy, female sex, and lower levels of C-reactive protein are associated with milder levels of ID in people with DS. Young children with DS are also more likely to have a mild form of ID than adolescents with DS. Other genetic disorders can also lead to mild ID: for example, most children with Williams syndrome also have mild ID. Microcephaly is also considered a risk factor for mild ID, with one study finding a 14.7% incidence of mild ID in children with developmental disabilities and microcephaly, compared to 9.5% for children with developmental disabilities and normal skull size. Birth injury and other birth-related factors can also increase mild ID risk. Advanced paternal age, uterine bleeding, birth via primary (first) Caesarean section, low Apgar score 5 minutes after birth, small size at birth for gestational age, and a need for assisted ventilation more than 30 minutes after birth are correlated with increased risk of mild ID. ==Prevalence==

About 1 to 3% of the world population has some form of intellectual disability, of whom 85% have mild ID. Estimates of the prevalence of mild ID vary, and can be inflated by the use of an IQ test as the sole measure to determine a person's ID status, since an ID diagnosis requires both a low IQ score and adaptive functioning deficits. In the United States and other developed countries, the rate tends to be around 2.5-5.0 per 1,000. ==Comorbidities==

Attention-deficit/hyperactivity disorder The most common comorbid disorder of mild ID is attention-deficit/hyperactivity disorder (ADHD). One study of 111 Turkish children with mild ID found that 64.9% also had ADHD, the most common psychiatric comorbidity by a factor of almost 3. Children with ADHD and mild ID are also more likely to have oppositional defiant disorder and symptoms of conduct disorder than children with ADHD and no ID. Developmental coordination disorder Developmental coordination disorder (also known as dyspraxia) and motor delay are common in people with mild ID. One study found that about 82% of children with mild ID have motor skills below the sixteenth percentile for their age group. Another study found that 89% of children with mild ID have motor skills below the sixteenth percentile for their age group, 92% of whom have motor skills within the bottom five percent of same-aged children. Adults with ID also tend to have below-average motor skills and show little hand preference in hand-eye coordination tasks. Autism Autism spectrum disorder is commonly comorbid with ID, including mild ID. About 24.1% of people with mild ID also have autism, but many of them do not get diagnosed until adolescence or later. Cerebral palsy Cerebral palsy (CP) is also associated with increased risk of mild ID, particularly among those with a GMFCS level of 3. ==Risks==

Children with mild ID in out-of-home care have a higher risk of sexual abuse than non-disabled children, with a frequency of 9.8 per 1,000 children. Among adults, the rate of sexual abuse is 24.3%. High-school students with mild ID are less likely to feel that they have the ability to share their opinions or make their own decisions or that working hard will lead them to attain their goals than students with learning disabilities and other, non-intellectual disabilities common among students receiving special education services. Older adults with mild ID are more likely to develop dementia than the general population: one study of mildly intellectually disabled older adults without Down syndrome found that 14.6% had dementia. ==References==