Stress can also arise from internal factors, as it happens for genetic and chromosomal anomalies.
The amount of internal stress could be a variable leading to multiple stress reactions. The link between stress and bruxism has a quite long and controversial history. The psychological stress was asserted as the main causal factor, according to experimental data, but it cannot fully explain the night bruxism. On other terms I expected to found more bruxism in Down Ss, with autism or PDD than in autistic or PDD Ss without Down syndrome or other illnesses. We checked out clinical records of all autistic or PDD children or young adults' one of us had in consultation since 1980.