The number of newborns who show symptoms of withdrawal from opioids, cocaine, hallucinogenic agents and other drugs is on the rise, according to inpatient discharge data collected by the Office of Statewide Health Planning and Development. After a brief dip a decade ago, the number of newborns exposed to drugs through their mother’s placenta or breast milk almost doubled from 2008 to 2015.

Nationwide, from 10 to 11 percent of newborns are estimated to have been exposed to alcohol or illicit drugs, according to the Department of Health and Human Services. Opioid withdrawal in newborns has increased nearly fivefold since 2000, a problem that is especially severe in rural areas, according to a February study in the medical journal JAMA. In California, it is unclear whether opioid abuse is driving the increase in drug-exposed infants.

Neonatal exposure to drugs and alcohol takes a toll: The substances can be easily transmitted to newborns through the placenta, and they target proteins that are crucial to neurological development, according to the journal Neuropsychopharmacology. Symptoms of withdrawal include tremors, irritability and difficulty sleeping — and nightmares can persist for up to six months, according to Adoptive Families. Research shows long-term effects can differ, and children in stable homes tend do well, according to the magazine.