It makes sense to me that sensory issues can play a very large part of shaping the world of some adoptees. While there are many possible reasons for challenges in this area, one is that the living conditions in which many international adoptees begin their lives are less than optimal. I thought I might try to to explain some of it.
Let's imagine the world of a newborn. It is unknown, uncertain, stimulating and magically gratifying. The baby poops, and he is cleaned up with loving tenderness; he is hungry and a warm breast (or bottle) appears making the world right again; too cold and he is warmed with a cuddle and a "blankie"; too loud and people are "shushed". There is fun cooing, smiling and singing when he is awake, and darkness when he needs to sleep. All is okay, enough of the time.
Let's switch to another possible scenario. This baby is in an orphanage He is likely in a crib most of the day, rarely held, fed from a bottle, propped up on a pillow, too awkward to reach; the air is too cold, or too hot; he poops but it takes a while to be cleaned up and it is in a hurried, brusque manner. He cries, but he must wait his turn, so he stops. He learns to play with his toes and fingers, sucks his thumb, plays with his hair...there are few toys. He grows and though his brain is ready to receive and use language there is little to hear and less to say. The precious window of opportunity when the brain is forming ways to integrate stimuli is slipping by, there is too little stimulation to learn how to organize it, how to focus on words through the sights and sounds around him, nor to regulate his impulses.
Fast forward...post-adoption, he needs help to foster the capacity to integrate stimuli, to focus on what's important, to un-attend to the irrelevant. The sensory system is on overload and short-circuits. Until he learns this process, behavior can be impulsive, out of control. With wisdom, acceptance and knowledgeable people to help take him through these developmental steps, he can begin to master the process that he missed. Then, learning can make leaps and bounds...