Some children suffer from scrupulosity, a form of OCD that involves a feeling of guilt and shame. Sufferers obsessively worry that they have committed blasphemy, been impure or otherwise sinned. They tend to focus on certain rules or rituals rather than the whole of their faith. They worry that God will never forgive them. And this can signal the onset of depression or anxiety, says John Duffy, a Chicago area clinical psychologist specializing in adolescents. “Kids who have made ‘mistakes’ with sex or drug use,” he says, “may have trouble forgiving themselves. “

Such fastidiousness to religious practices may not seem so harmful, but extreme behavior such as delusions or hallucinations may be a sign of serious mental illness. Seeing and hearing things that are not there can be symptoms of manic-depressive, bipolar disorder, or early onset schizophrenia. But parents may be less attuned to such unhealthy behavior when it occurs under the guise of faith.