There's probably no big surprise associated with the findings of this recent study. However, a few findings worthy of particular note are that the negative affects linger on well after an adolescent has stopped using marijuana, and that adolescent girls are more at risk than boys for suffering the affects.
A recently released study suggests that chronic, heavy marijuana use during adolescence – a critical period of ongoing brain development – is associated with poorer performance on thinking tasks, including slower psychomotor speed and poorer complex attention, verbal memory and planning ability. Krista Lisdahl Medina, a University of Cincinnati assistant professor of psychology and a lead researcher of the study, says that's evident even after a month of stopping marijuana use. She says that while recent findings suggest partial recovery of verbal memory functioning within the first three weeks of adolescent abstinence from marijuana, complex attention skills continue to be affected.
"Not only are their thinking abilities worse, their brain activation to cognitive tasks is abnormal. The tasks are fairly easy, such as remembering the location of objects, and they may be able to complete the tasks, but what we see is that adolescent marijuana users are using more of their parietal and frontal cortices to complete the tasks. Their brain is working harder than it should," Medina says.
She adds that recent findings suggest females may be at increased risk for the neurocognitive consequences of marijuana use during adolescence, as studies found that teenage girls had marginally larger prefrontal cortex (PFC) volumes compared to girls who did not smoke marijuana. The larger PFC volumes were associated with poorer executive functions of the brain in these teens, such as planning, decision-making or staying focused on a task.