Intellectual disability (ID), also called intellectual development disorder (IDD) or general learning disability, and formerly known as mental retardation (MR) is a generalized neurodevelopmental disorder characterized by significantly impaired intellectual and adaptive functioning. It is defined by an IQ score below 70 in addition to deficits in two or more behaviors that affect every day, general living.
Pathophysiology: Sometimes disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons eg. Down syndrome, Klinefelter's syndrome, Fragile X syndrome (common among boys), neurofibromatosis, congenital hypothyroidism. Intellectual disability can result when the fetus does not develop properly.
Diagnosis: The three criteria must be met for a diagnosis of intellectual disability: deficits in general mental abilities, significant limitations in one or more areas of adaptive behavior across multiple environments and evidence that the limitations became apparent in childhood or adolescence. In general, people with intellectual disability have an IQ below 70, but clinical discretion may be necessary for individuals who have a somewhat higher IQ but severe impairment in adaptive functioning.
The recent Singapore Mental Health Study 2010 found that about one in 10 people in Singapore suffer from a mental disorder. Major Depressive Disorder, Alcohol Abuse and Obsessive Compulsive Disorder were found to be the top three most common disorders here. One in 17 people in Singapore have suffered from MDD at some time in their lifetime, while Alcohol Abuse and OCD affected one in 32 and one in 33 people, respectively. According to the study, MDD was the most common mental illness in Singapore.