Global Developmental Delay has vastly wider definition than Learning Disabilities. The first difference that has to be noted is factors that determine these two. GDD has many known factors, mainly genetic defects or severe medical problems. Factors which cause LD are still unkown, although probably will apply to the same areas - genetics and health. Still, damage in LD is not as severe as in GDD. LD mainly refer to disabilities such as dyslexia, dysgraphia and so on. These do not affect intelligence, unlike GDD.

I think you should start to look for a proper definitions which cover all of the areas of child functioning - language and speech, senses, motor, cognitive, social and emotional skills. You can search through ICD-10 and some psychological resources.

Here you have some article that covers the problem of evaluation of children with GDD:

http://www.neurology.org/content/60/3/367.short

and a book concerning learning disabilities - I cannot tell anything about the contents but after looking at the authors who are strongly involved in education and pedagogy I think it can be useful:

http://books.google.pl/books?id=Ud4hjaz2nisC&hl=pl

Global developmental delay is used for children with developmental progress falling significantly behind age expectations (generally 2 SD below mean or more) in multiple domains (e.g cognition and language and/or motor skills).

Best practice is for the term not to be applied once an IQ can be reliably assessed. Partly because a learning disability can then be fairly definitively diagnosed but also partly because the use of the term "delay" suggests the possibility of resolution. Once these levels of delay are persisting to about 4 years then they are highly unlikely to resolve.

I would recommend you look at Shevell's work….

Basically, Global Developmental Delay (GDD) is more general than Learning Disabilities (LDs). In other words, the former might include latter and vice versa. In LDs, four issues are to be accounted for: Language skills (Listening, Speaking, Reading, Writing) in addition to Maths and Reasoning. The reasons of what happen are not well-known, but they might be sometimes some symptoms of GDD. By all means, the two terms are technically and principally different and you can consult other books, articles which will give you more details in this issue. For free download of books, please visit this website:

http://book4you.org/