Can long-term nose blockage and breathing difficulty cause slow brain development and low IQ? My son is 22 years old. He couldn’t complete graduation and always had poor scores in school. Recently, doctors confirmed he has low IQ and intellectual disability. Since birth, he always had running nose and thick mucus (yellow or green). His nose often got blocked, and he had difficulty breathing through his nose. Even after cleaning, it used to fill again within minutes. We neglected this problem for many years. At age 18, we consulted an ENT doctor and it got cured. Now I have a question — Can long-term mucus-filled nose and breathing difficulty since childhood affect brain development or cause low IQ, even if the body growth is normal (taller and bigger than others)? Or this cannot be the reason for his low IQ? MRI of brain is not yet done. Should we get it done to check for any effect on brain development?