Can Cognitive Development Delays be overcome?

I have one Ds who has mild? moderate? cognitive delays. He was very delayed, developmentally, as an infant. He kind of caught up with developmental milestones by around age 2 or 2.5. He didn't speak until about age 4, though, so he had a significant speech delay. At age 3.5 he had maybe 35 words, including sign, which doesn't count for verbal vocabulary. He did move forward well after about age 4, but he didn't suddenly began to speak in sentences or anything. He progressed at about the same way that a toddler aquiring vocabulary would. A few words a month, incrementally.He has learning lags, and learning disabilities. I believe these are related to his prenatal exposure to multiple drugs and alcohol. He was born addicted. At age 9 there are still some areas where he's not at the same level as his chronological peers. He has what they call 'dysmaturity', which just means that he doesn't function at a 9 yo level in all areas. His 'inside age' doesn't match up with his 'outside age'. It's hard to describe because he is NOT mentally retarded, but he functions around maybe a 6 yo level in some areas, while in others he's much higher, perhaps even higher than his chronological age. So it's misleading to say 'he's 9, but is really 6', even though in some areas he's 6. Sort of. LOLA person can overcome some cognitive delays, but like Alys says, it depends on why there are cognitive delays. Delays due to lack of training are probably more easily overcome. ("Easily" being a relative term.) Cognitive issues from TBI (traumatic brain injury, like CP, for instance, or anoxia at birth), or from drugs/alcohol can take more work, but may be diminished with time and lots of work. It truly depends on the kinds of problems and their cause. HOWEVER new research now shows that the brain CAN heal and change. So it's work, but often the brain can recover. The exact extent of brain recovery, though, depends on many variables.