Developmental disabilities are birth defects that cause lifelong problems with how a body part or system works. They include

• Nervous system disabilities affecting how the brain, spinal cord and nervous system function. They cause mental retardation, including Down syndrome and fragile X syndrome. They also cause learning and behavioral disorders, such as autism
• Sensory-related disabilities, which can cause vision, hearing and sight problems
• Metabolic disorders such as phenylketonuria, which affect how your body processes the materials it needs to function
• Degenerative disorders such as Rett syndrome, which might only become apparent when children are older and can cause physical and mental problems

Most developmental disabilities have no cure, but you can often treat the symptoms. Physical, speech and occupational therapy might help. Special education classes and psychological counseling can also help.

Developmental disabilities used to be referred to as mental retardation. The broadening of the term corresponds to changes in the way that individuals with developmental disabilities are viewed, cared for, and integrated into society.

30 years ago infants born with obvious signs of a developmental disability (such as Down Syndrome) were often referred directly to an institution where they could be raised. Many people with mental retardation were institutionalized with variable involvement with their families and communities. More recently, individuals with disabilities are increasingly recognized as an important part of the fabric of society, and integration has become the starting point for issues like education and health care.

A development in the rearing and education of mentally retarded individuals was the "normalization principle" that recognized that meaning was created in the lives of such individuals through the same kind of daily, yearly, and lifetime milestones as all people. This referred to having a predictable daily schedule with separation between work and leisure, an annual schedule that provided for vacations, and marking of developmental milestones that distinguished between childhood and adulthood, for example, and distinguished between the "working years" and the older years of retirement.

For the last 15 years or so in the US there has been a shift in caring for individuals with disabilities to more integration into communities. Thus children with developmental disabilities are being raised at home in their families and educated in community schools. School programs integrate individuals with disabilities into regular classes as much as possible. Secondary education focuses on vocational preparation, and individuals with disabilities are assisted in getting and holding jobs. Individuals with disabilities are more often living in communities, in group homes or semi-independent, and many institutions for individuals with developmental disabilities have been closed.

Because of the broader inclusion of persons with developmental disabilities in our communities, mental health professionals, medical professionals, and members of the community, including family members, employers, educators, and clergy seek a broader understanding of the needs and responses of individuals with developmental disabilities.

Definition: Developmental Disabilities refer to disabilities that affect a range of social and cognitive areas including communication, learning, judgment, and interpreting and responding to social cues. Generally developmental disabilities are present at birth or considered to be intrinsic to the organism (i.e. not acquired through illness or accident, except when the incident occurs early enough to significantly interfere with acquisition in the social and cognitive areas as defined above).

They are distinguished from the mental illnesses in a variety of ways. First they are generally stable or progressive, but not generally relapsing and remitting. Second they primarily affect cognition and perception, and are not necessarily associated with distortions in thinking or with affective disturbances. It is important to remember that people with developmental disabilities may also have treatable mental illnesses