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Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults

, : Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults. Cmaj 166(7): 887-891

Assessing marijuana's impact on intelligence quotient (IQ) has been hampered by a lack of evaluation of subjects before they begin to use this substance. Using data from a group of young people whom we have been following since birth, we examined IQ scores before, during and after cessation of regular marijuana use to determine any impact of the drug on this measure of cognitive function. We determined marijuana use for seventy 17- to 20-year-olds through self-reporting and urinalysis. IQ difference scores were calculated by subtracting each person's IQ score at 9-12 years (before initiation of drug use) from his or her score at 17-20 years. We then compared the difference in IQ scores of current heavy users (at least 5 joints per week), current light users (less than 5 joints per week), former users (who had not smoked regularly for at least 3 months) and non-users (who never smoked more than once per week and no smoking in the past two weeks). Current marijuana use was significantly correlated (p < 0.05) in a dose-related fashion with a decline in IQ over the ages studied. The comparison of the IQ difference scores showed an average decrease of 4.1 points in current heavy users (p < 0.05) compared to gains in IQ points for light current users (5.8), former users (3.5) and non-users (2.6). Current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week. A negative effect was not observed among subjects who had previously been heavy users but were no longer using the substance. We conclude that marijuana does not have a long-term negative impact on global intelligence. Whether the absence of a residual marijuana effect would also be evident in more specific cognitive domains such as memory and attention remains to be ascertained.


PMID: 11949984

Other references

Galileo, M.H.M.; Martins, U.R., 1990: Longhorn beetles of the emilio goeldi museum of para brazil i. new species in sphaerionini and onciderini coleoptera cerambycidae. New species described from Para, Brazil: Nyssicostylus overali, sp.n. (Sphaerionini, Cerambycinae), Trestonia exotica, sp. n. and Pseudobeta ferruginea, sp. n. (Onciderini, Lamiinae).

Valerio, D.; McIvor, R.S.; Williams, S.R.; Duyvesteyn, M.G.; van Ormondt, H.; van der Eb, A.J.; Martin, D.W., 1984: Cloning of human adenosine deaminase cDNA and expression in mouse cells. A previously isolated partial cDNA sequence encoding human adenosine deaminase (ADA) was used to probe a cDNA library prepared from human cultured cell mRNA. Clones containing a combined overlapping length of 1462 bp were isolated and sequenced. O...

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Radojcić, L.; Mijanović, D.; Dokić-Nikolić, M., 1997: Levels of progesterone, estrogen, FSH and LH in galactorrhea of unknown etiology. Considering the frequent occurrence of idiopathic galactorrhea in the women of fertile age, the hormone status was investigated in 50 patients aged from 20 to 40 years. The FSH, LH, estradiol and progesterone hormones were tested. The hormone leve...

Grabow, C.; Grosskinsky, S.; Kurths, Jürgen.; Timme, M., 2016: Collective relaxation dynamics of small-world networks. Complex networks exhibit a wide range of collective dynamic phenomena, including synchronization, diffusion, relaxation, and coordination processes. Their asymptotic dynamics is generically characterized by the local Jacobian, graph Laplacian, or...

Petrov, M.P., 1966: A review of literature on the reclamation of desert- and semi-desert sands in the USSR for 1965. This is a list of 106 annotated references to the natural conditions and vegetation of desert- and semi-desert sands and to their reclamation by the planting of windbreaks or sowing herbage plants.

Rusko, J.; Van Breemen, C.; Adams, D.J., 1993: Caffeine-induced calcium release from intracellular stores in freshly dissociated endothelial cells from rabbit aorta. Journal of Physiology (Cambridge) 459(0): 256P

Kotzerke, J.; Gabelmann, A.; Hanke, H., 2002: Recurrent renal artery stenosis--endovascular brachytherapy with a rhenium 188 filled balloon catheter. Rofo 174(9): 1176-1178