A long-term study of more than 11,000 children and teens has linked recreational cannabis use to slightly slower development of memory, attention, and thinking skills. The findings add to public health advice that teens should avoid cannabis use, as it may harm the developing brain. "Adolescence is a critical time for brain development, and what we're seeing is that teens who start using cannabis aren't improving at the same rate as their peers," says neuropsychologist Natasha Wade from UC San