Causes of Stuttering Stuttering is a complex condition. Even after decades of research, the exact causes are unknown. However, many experts believe that a combination of genetic, physical, and psychological factors are involved. There is also general agreement that stuttering probably is not caused by: Emotional or psychological trauma Shyness or fear of meeting or speaking to people Poor upbringing or inadequate parenting In adults, it’s very rare for stuttering to begin in a person who's never stuttered before. If you suddenly begin stuttering, it may be a sign of a more serious medical problem; see a doctor immediately.