Short-term memory impairment in cannabis-dependent adolescents
R. H. Schwartz, P. J. Gruenewald, M. Klitzner and P. Fedio
Department of Pediatrics, Georgetown University School of Medicine, Washington, DC.
The concentration of delta-9-tetrahydro-cannabinol in marijuana available
in the United States has increased by 250% since investigations of the
effects of marijuana on short-term memory first appeared in scientific
journals. Moreover, previous investigations of short-term memory in
long-term marijuana smokers involved adults only. We evaluated the
auditory/verbal and visual/spatial memory of 10 cannabis-dependent
adolescents and compared the results with performance of 17 subjects in two
control groups. The control groups included 8 adolescent drug abusers who
had not been long-term users of cannabis and another 9 adolescents who had
never abused any drug. All three groups were matched on age, IQ, and
absence of previous learning disabilities. Adolescents with a history of
frequent alcohol or phencyclidine abuse were excluded from entering the
study. A battery of seven neuropsychological tests was administered
initially to all subjects and a parallel test battery was administered 6
weeks thereafter. Significant differences between the cannabis-dependent
group and the two control groups were obtained initially on the Benton
Visual Retention Test (F[2,24] = 6.07) and the Wechsler Memory Scale Prose
Passages (F[2,23] = 7.04). After 6 weeks of supervised abstention from
intoxicants, subjects in the cannabis-dependent group showed some
significant improvement on the Wechsler Memory Prose Passages score and on
the Benton Visual Retention Test; however, the improvement failed to
achieve statistical significance. We concluded that cannabis-dependent
adolescents have selective short-term memory deficits that continue for at
least 6 weeks after the last use of marijuana.
