You know your child best. If your child has developmental barriers, let's keep a few things in mind.
1) Even if your child is 6 months old, they are going to get older. Circumstances will change. The topography of behavior will change. Their preferences will change. The same is true for your child as they turn 1, 5, 11, et cetera. Some things will be messy, others will be seamless. Do not expect anything -- do your best to be proactive, but also take as they come. Learn from what has happened, and be proactive therein.
2) There is a terrible misunderstanding that certain diagnoses present in fairly predictable ways. Children with barriers are still individuals. If you and your friend had children around the same time, and they began to present with certain symptoms around the same time, this does not mean that your other friend's child will develop in the same way.
3) What worked over the Summer, may not work in the Fall. Read into and think about this statement.
4) What is a milestone for a similar child may not happen with your child until much later, but they may have met milestones that their counterpart has not.
5) Be careful what hype you buy in to. There are a few hundred therapies for children with disabilities, and less than a dozen that have empirical, scientific evidence that they actually prove effective.
Finally, people are not just one thing. There are always competing factors, other diagnoses, quirks, and preferences that need to be considered. Remember that. There is never a single root to any one cause.