Children who have been in the womb and have been exposed to cannabis are more likely to suffer from anxiety, to show signs of aggression and hyperactivity.
A study of 322 babies and their mothers found that more and more pregnant women were considering using cannabis as a way to relieve nausea and pain, so studying this trend is vital, said lead author Jasmin Hard.
The study was one of the first to directly examine the link between cannabis and children, said Daniel Piomeli, director of the Center for Cannabis Research at the University of California.
Current research is not yet final, but doctors advise pregnant women to refrain from using cannabis. Cannabis also increases the risk of preterm birth, low birth weight and autism.
Scientists examined samples of placentas from mothers after childbirth and analyzed their genetic makeup. When babies were three years old, they tested samples of their hair and heart rate to see their reactions to stress.
They also assessed anxiety, aggression and hyperactivity. The tests were repeated until the children were six years old. Children whose mothers consumed cannabis during pregnancy had dysfunctional placental tissue, which reduced the immune response. They were also anxious, aggressive and hyperactive.