and Long-Term Use of Ganja (Cannabis)
1981, Volume 213, pp. 465-466 SCIENCE
Schaeffer, Therese Andrysiak, and J. Thomas Ungerleider
1981 by the American Association for the Advancement of Science
variables and urine cannabinoid metabolites were evaluated in ten subjects
born, raised, and educated in the United States and having histories
of heavy or prolonged use of cannabis.
No impairment of
cognitive function was found. Cannabinoid metabolites in excess of 50
nanograms per milliliter were present in the ten urine samples. The
tetrahydrocannabinol content of cannabis exceeded 8.0 percent.
have attempted to characterize the mental or cognitive functioning of
persons with histories of heavy and prolonged use of ganja (cannabis).
Generally, investigators have concluded that heavy and prolonged use
has not led to impairment of mental and cognitive functions consistent
with brain or cerebral dysfunction (1-4).
studies have shown decrements in neuropsychological performance among
those with brief or sporadic patterns of cannabis use here in the United
States (5-9), comparable studies of prolonged heavy use in this country
have not been performed. Thus, the only available literature is based
on studies conducted in foreign countries (Jamaica, Greece, Egypt, and
We had the opportunity
to observe a group of long-term heavy users of ganja in both a Southern
state and a Caribbean island. The ganja was used by this group for religious
purposes and symbolized the sacrament of communion--"the Green
Herb of the Bible." It was used, as we observed, even during the
extensive neuropsychological evaluations that we completed, in a continuous
and ritualistic manner throughout virtually all waking hours. Very large
cigarettes (or "spliffs") and pipes, containing ganja mixed
with tobacco, were regularly shared by members of the group (10).
We examined ten
subjects (seven males and three females) ranging in age from 25 to 36
years. The mean number of years of education was 13.5 (all were born,
raised, and educated in the United States), and all were Caucasian.
None had any history of disease that could be related to central nervous
system dysfunction. By their own report, they used between 2 and 4 ounces
of the ganja-tobacco mixture per day, with a reported mean duration
of use of 7.4 years (the time since joining this particular church).
All subjects actively engaged in daily work, largely agricultural and
business, and led active and spiritually oriented lives (10). It was
not possible to collect control data in this environment, as all church
members continuously smoked ganja. Thus, comparisons were made with
the published standards and normative data for the psychometric instruments
Subjects in this
study agreed to provide approximately 15 ml of fresh urine for enzyme
immunoassay of cannabinoid metabolite content. Specimens were preserved
with approximately 4 mg of sodium azide per 15 ml of urine that was
collected. Urine samples for each of the ten individuals studied were
obtained immediately before each subject began a series of selected
neuropsychological tests designed to assess a broad range of cognitive
A modified version
of the Michigan Neuropsychological Test Sequence was used (11-13). Each
subject was administered exactly the same group of tests in exactly
the same order. General intellectual functioning was assessed on the
basis of a prorated version of the Wechsler Adult Intelligence Scale
(Table 1) (14). Additional neuropsychological tests included the following:
Benton Visual Retention Test (administration C) (15), Rey Auditory-Verbal
Learning Test (16), Symbol-Digit Modalities Test (17), Hooper Visual
Organization Test (18), Raven's Progressive Matrices Test (19), and
Trailmaking Test (forms A and B) (20). The following cognitive functions
were assessed: language areas of function, nonlanguage areas of function,
memory, complex multimodal learning, and general intellectual functioning.
Auditory and visual memory functions included remote (years and months),
recent (weeks, days, hours, minutes), and immediate events (within seconds).
An enzyme immunoassay
method (Emit-d.a.u.) (21) was used to analyze urine samples. The assay
is a semiquantitative immunochemical test designed to detect a
level of at least 50 ng of 11-nor-delta-9-tetrahydrocannabinol cabboxylic
acid per milliliter of urine with greater than 95 percent confidence.
Each of the ten urine samples contained concentrations of cannabinoids
at 50 ng/ml (one subject) or well above this level (nine subjects).
None of the neuropsychological
test data indicated impairment of cognitive functioning. Language areas
of function, nonlanguage areas of function, memory, complex multimodal
learning, and general level of intellectual functioning were all completely
unimpaired, compared with standardized-normative information available
for each test (Table 1).
The mean IQ scores
(Table 1) are all in the superior to very superior range of intellectual
functioning, ranging from the upper 6.7 percent to the upper 2.2 percent
of the population (14). Scores obtained on all of the other psychometric
tests were also well within the normal range for age (11-20). There
was nothing found in any of the ten subjects' protocols that might suggest
impaired mental functioning due to brain or cerebral dysfunction resulting
from heavy and prolonged use of ganja.
While several previous
studies have reported transient cognitive impairment resulting from
the acute effects of cannabis, primarily with respect to attention-concentration
and visuomotor (hand-eye) coordination (8, 9, 22, 23), none of the studies
involving prolonged and heavy use of ganja have shown any systematic
decrements in mental abilities suggestive of impairment of brain or
cerebral function and cognition (14).
We also included
toxicologic verification of urinary cannabinoid metabolites, observed
the inhalation of cannabis by all subjects studied, and analyzed samples
of this cannabis for THC. Analysis of cannabis mixed with tobacco (by
gas chromatography) yielded a delta-9-THC content of 4.14 percent (half
cannabis, half tobacco); thus the THC content of the pure cannabis exceeds
8.0 percent. We observed no transient decrements in cognitive functioning
that often accompany intermittent or sporadic use of cannabis. The development
of tolerance to one or more of the constituents of cannabis may
explain this phenomenon.
Although the obtained
IQ scores were high, one could speculate that perhaps cannabis had produced
a priori declines in IQ scores for all ten subjects, as well as scores
on other neuropsychological measures. It was possible for us to obtain
early school academic achievement test data on two of our subjects.
These data included equivalent IQ conversion scores virtually identical
to those we measured for those subjects. We realize that these conversion
or equivalent IQ scores derived from early school achievement test data
are not to be equated on a one-for-one basis with current scores. However,
we do believe that IQ score ranges provide a reasonable degree of equivalency.
These achievement test scores were obtained some 15 to 20 years earlier,
long before either subject began the use of cannabis, by their report
Finally, we stress
the commitment of the ten subjects to their religious sect and way of
life. They told us and others (10) that members of the church do not
use substances (drugs, alcohol, or psychoactive herbs other than ganja,
and we observed them to maintain a regular diet consisting primarily
of vegetables, fruit, and small amounts of meat. All ten subjects (as
well as other members of the church) appear to be healthy and highly
functional individuals adhering to a strict religious doctrine.
Department of Psychiatry
and Biobehavioral Sciences. University of California School of Medicine,
Los Angeles 90024,
Los Angeles 90048
J. THOMAS UNGERLEIDER
Department of Psychiatry
and Biobehavioral Sciences, University of California School of Medicine
Table 1. Summary
of neuropsychological data (means ± standard deviations).
Wechsler Adult Intelligence
Full-scale IQ* 26.2
15.2 ± 2.10
20.8 ± 2.30
69.6 ± 8.73
42.7 ± 5.96
29.1 ± 5.30
129.0 ± 10.87
124.2 ± 13.07
128.4 ± 10.36 16.5
14.3 ± 1.95
14.2 ± 1.97
13.8 ± 2.49
13.8 ± 2.39
13.0 ± 2.98
Form B 8.8 ± 1.02
14.9 ± 0.32
60.4 ± 10.25
28.7 ± 1.06
35.2 ± 0.79
28.8 ± 6.88°
53.5 ± 15.28°
*Prorated. °No errors.
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L. Comitas, Ganja in Jamaica (Mouton, The Hague, 1975).
2. M. C. Braude
and S. Szara, Eds., Pharmacology of Marijuana (Raven, New York, 1976).
3. R. L. Dornbush
and A. Kokkevi, in (2), p. 421.
4. C. Stefanis,
J. Boulougouris, A. Liakos, in (2), pp. 659-665.
5. I. M. Frank,
P. J. Lessin, E. D. Tyrrell, P. M. Hahn, Szara, in (2), pp. 673-679.
6. S. Y. Hill and
D. W. Goodwin in (7), p. 139.
7. S. Cohen and
R Stillman, Eds., The Therapeutic Potential of Marijuana (P1enium, New
8. L. L. Miller,
in (7), pp. 271-292.
9. R. T. Jones and
N. Benowitz, in (2), p. 627.
10. M. C. Dreher,
personal communication (March 1980).
11. A. Smith, in
Drugs, Development and Cerebral Function. W. L. Smith, Ed. (Thomas.
Springfield, Ill., 1972), pp. 27-68.
12. _____ and C.
W. Burkland, paper presented at the annual meeting of the American Psychological
13. _____, Science
153, 1280 (1966).
14. D. Wechsler,
Manual for the Wechsler Adult Intelligence Scale (Psychological Corporation,
New York, 1955).
15. A. Benton, Revised
Visual Retention Test: Clinical and Experimental Applications (Psychological
Corporation, New York, ed. 4, 1974).
16. M. Lezak. Neuropsychological
Assessment (Oxford Univ. Press, New York, 1976).
17. A. Smith, Symbol
Digit Modalities Test Manual (Western Psychological Services, Los Angeles,
18. E. Hooper, The
Hooper Visual Organization Test (Western Psychological Services, Los
19. J. C. Raven,
Guide to Using the Coloured Progressive Matrices (Lewis, London, 1965).
20. R. M. Reitan,
Percept. Motor Skills 8, 271 (1958).
Urine Assay: Emit Cannabinoid Assay (Syva, Palo Alto, 1980).
22. R. A. Harshman,
H. Crawford, E. Hecht, in (7), pp. 205-254.
effects," in Marihuana Research Findings (National Institute of
Drug Abuse Monorgaph No. 14, Government Printing Office, Washington,
D.C., 1977), p. 128. 23 September 1980; revised 9 January 1981 Individual
results for Carl Olsen