“Overall, these results suggest that, in addition to academic failure, fundamental life skills necessary for problem-solving and daily adaptation may be affected by early cannabis exposure,” said the researchers.
As many as 294 teenagers completed a variety of cognitive tests at ages 13, 14 and 20 and filled out a questionnaire once a year from ages 13 to 17 and again at 20, between 1991 and 1998.
Roughly half -43 per cent -reported smoking pot at some point during that time, most of them only a few times a year.
At 20 years of age, 51 per cent said they still used the drug. In general, those who started early already had poor short-term memory and poor working memory (the ability to store information such as a phone number long enough to use it, or follow an instruction shortly after it was given).
Conversely, the early users also had good verbal skills and vocabulary.