RT Journal
A1 Kuehn BM
T1 MArijuana use starting in youth linked to iq loss
JF JAMA
JO JAMA
YR 2012
FD September 26
VO 308
IS 12
SP 1196
OP 1196
DO 10.1001/2012.jama.12205
UL http://dx.doi.org/10.1001/2012.jama.12205
AB 
Heavy use of marijuana has been previously linked to neuropsychological impairment, particularly when use begins early in life. But much of this evidence came from case-control studies, which may be vulnerable to certain biases. The latest study followed up 1037 individuals in New Zealand from their births in 1972 or 1973 until age 38 years. Participants underwent neuropsychological testing at age 13 years to develop a baseline and were tested again at age 38. Interviews were conducted with patients at ages 18, 21, 26, 32, and 38 years to assess cannabis use.