of a study on ganja in Jamaica
Cultivation of ganja
The ganja trade
Ganja use and farming
Ganja production and food requirements
Ganja use and the "motivational syndrome"
Clinical studies of ganja users The sample
G. G. NAHAS
Pages: 15 to 29
Creation Date: 1985/01/01
G. G. NAHAS
Department of Anesthesiology, College of Physicians and Surgeons of Columbia
University, New York, N. Y., United States of America
In the study of
"Ganja in Jamaica" by Rubin and Comitas, no significant differences
between heavy ganja smokers and controls could be demonstrated in physical
and psychological symptoms or social adjustment. This lack of difference
may be attributed to methodological limitations in the sampling technique
and examinations performed. The number of subjects studied was small
(30 in both control and test group). The selection of controls was inadequate:
only 12 controls had never smoked ganja, and 8 were current occasional
users. Methodological limitations flawed the physical examinations of
the lung and cardiovascular system, cytogenetic studies, psychological
assessment and psychiatric evaluation. Acceptance by the authors of
a positive motivational influence of cannabis smoking and other socially
beneficial properties of such smoking was based more on philosophical
premises than on objective observations performed by others in Jamaica
and other countries.
In 1971, the Center
for Studies of Drug Abuse of the National Institute on Mental Health
contracted the Research Institute for the Study of Man, New York, to
conduct a study of the effects of chronic cannabis smoking in Jamaica.
V. Rubin and L. Comitas, specialists in anthropology and professors
at the Teachers College of Columbia University, New York, undertook
the study in co-operation with the Faculty of Medicine, University of
the West Indies, Jamaica, and published its results in 1975 under the
title "Ganja in Jamaica, a Medical Anthropological Study of Chronic
Marijuana Use"  . As the
conclusions of this study have had a considerable influence on cannabis
control policy in Jamaica and elsewhere, this article is written in
an effort to provide a critical appraisal of the study, which has never
been so far made.
Cannabis was brought
to Jamaica in 1845 by indentured labourers from India, who called it
ganja, as they did in their native land. The habit spread first among
the lowest socio-economic classes. Eventually, numerous reports attributing
episodes of insanity to ganja smoking aroused public concern, and in
1913 the Government banned cultivation and import of the plant. Despite
those measures, the use of the drug spread, which prompted the enactment
of more severe legislation in 1924. During the late 1930s a cult arose
whose members were called "Rastafarians". They believed that ganja was
a holy plant, and smoking it was part of their religion. These cultists
popularized ganja smoking, particularly in the form of the "spliff",
a four-inch cigar made of a mixture of ganja and tobacco. In 1941, the
Government again increased the penalty for ganja smoking and its legislation
became the harshest in the world against cannabis.
During the years
following the Second World War, the problem of ganja remained a public
concern and both the Government and the mass media strongly condemned
its use. During the 1960s, civil disorder fuelled an attitude that associated
ganja smoking with criminality. As officials became aware that ganja
had become a cash crop instead of one grown only for domestic consumption,
laws were further strengthened in 1961, the year before Jamaica gained
its independence. In the period following independence, the ganja problem
remained a concern because domestic use, as well as illegal export,
continued to increase.
In 1972, the national
authorities in Jamaica adopted a more liberal attitude towards dealing
with the problem of ganja smoking, which was similar to the approaches
emerging in the United Kingdom of Great Britain and Northern Ireland
and the United States of America. One of the first legislative actions
taken by the authorities in Jamaica was to introduce a bill abolishing
mandatory sentencing for ganja offences. Passage of the bill was facilitated
by the results of the study. The study, which essentially exonerated
ganja from causing any damaging effects on mind, body and society that
had previously been attributed to the drug, was used to bolster the
arguments of Jamaican authorities for more lenient laws.
Since the elimination
of mandatory sentencing for cannabis offenders ganja trafficking has
flourished. During the late 1970s the export of agricultural products
from Jamaica stagnated, while the illicit exports of cannabis, mainly
to the United States, reached a high level, making this drug the major
cash crop of the country. Currently it is a billion-dollar enterprise.
Small farmers depend for survival on its cultivation and sale, and the
scions of some of Jamaica's well-known families have become marijuana
entrepreneurs. The burgeoning marijuana traffic poses many problems
for the future of Jamaican society. The situation is similar in other
countries, such as Colombia, Morocco and Lebanon, where cannabis is
illegally produced by semi-literate farmers who scrape a bare existence
from growing and selling it while affluent entrepreneurs derive handsome
prof its from its trade, thus fostering an illegal enterprise that becomes
a major source of corruption.
The use of the
study to justify a change in marijuana law in Jamaica demonstrates the
impact of the study on Jamaican policy. The conclusions of the study
also had repercussions on the marijuana debate in other countries. It
provided compelling arguments for those who advocated a policy of decriminalization
and social acceptance of marijuana use. In the United States, for example,
Consumers Report in 1975 relied heavily on the study in describing
the medical effects of cannabis 
; its findings were favourably echoed in the New York Times
and the San Francisco Chronicle
; a review of the study in Science indicated that it was "the
most significant set of findings on cannabis ever assembled in a single
study"  . Such prestigious
lay and scientific publications reinforced the opinion of the American
public that marijuana use was not particularly hazardous to health.
Following the publication of the report on the study 
, pro-marijuana organizations in the United States such as the National
Organization for the Repeal of Marijuana Laws intensified their lobbying
efforts for decriminalization. The report on the study was also widely
circulated in Western Europe for the same purpose.
has been widespread acceptance of the report on the study, it has never
been critically appraised. Many physicians and scientists, including
the author of this article, believe that the conclusions of the study
are not justified, even by its own data. In addition, the medical part
of the report on the study was fraught with basic methodological errors
and major omissions in the selection of the sample of subjects and in
the analysis of both their performance on the tests and the recorded
data. The social scientists who directed the study identified with the
plight of destitute farmers whose ganja use formed part of a life-style
which did not seem at the time to be seriously detrimental either to
themselves or to their community.
The report on the
study was divided into the following three parts: an ethnological study
of the importance of ganja in Jamaican society; clinical studies of
ganja users; and socio-cultural generalizations concerning the use of
ganja. The methodology adopted and conclusions reached are described
and critically analysed below.
one urban and six rural, were chosen for the study. Results from only
two of the rural communities were described in the final report.
In one rural community,
a group of 178 men over 15 years of age representing different social
classes was studied. One half of them admitted having smoked ganja at
one time or another, but the investigators did not specify the amount
or potency of the drug consumed either by "occasional smokers" who took
it three or four times a week or by "chance smokers" who took a draw
when offered. Of those who smoked ganja, 50 percent used one or more
ounces of the drug daily (
, p. 48). Of the 178 men in the group studied, 47 were either former
smokers or "unclassifiable". Among the ganja smokers, the majority were
from the lowest social class. Out of 20 from the upper social class
four were occasional users.
Since the use of
ganja was so pervasive in the communities studied, it was not possible
to find enough non-ganja smokers who could constitute a control group.
Of the 36 men who reported to have been non-smokers, 11 were from the
upper social class.
The most frequent
method of marijuana use was the spliff, which was preferred to the "chillum",
a large pipe shared by several users. The method of smoking was similar
to that reported elsewhere: one "inhales deeply, holds the smoke as
long as possible and exhales slowly" (
, p. 47). Other ganja preparations were also used. For example, ganja
tea, made with ganja leaves and sticks with sugar and milk added, was
used by 48 per cent of the households surveyed. Usually prepared by
the women, ganja tea was frequently given to children in the belief
that it would improve the functioning of the brain. Ganja tea drinkers
were not usually smokers. Ganja tonics, concoctions of green or dried
plant material mixed with rum or wine, were popular as multi-purpose
medicine, which were often used daily. Such preparations were also recommended
for soothing troublesome infants and children. The investigators did
not measure the content of tetrahydro-cannabinol (THC) and other cannabinoids
of those preparations, nor was their frequency of use established among
ganja smokers or non-smokers.
Ganja use in depressed
socio-economic classes began in infancy with the introduction of ganja
tea and tonics. Actual smoking began in adolescence, especially in households
where fathers were regular smokers. Boys began smoking as early as 10
years of age and became habitual smokers when they earned their living.
Adolescents smoked ganja in relatively large groups dominated by youthful
vendors. Smoking ganja was seen as a kind of rite of passage, an audacious
act, signifying the transition from adolescence to maturity. Patterns
from occasional to steady use were thus established, but information
about them did not include any data concerning sex distribution, relative
frequency of use, impact on school attendance, learning, occupation
or social mobility ( , p.
As a result of
widespread use of ganja in the community, consumers who were also farmers
devoted part of their time both to the cultivation and distribution
of ganja. Out of 153, 39 "identifiable" households in the community
studied were occupied with the cultivation of ganja, but in fact, there
might have been many more. Of them, 22 grew ganja for personal use and
17 for outside distribution. All but five households belonged to the
lowest social segment of the population. The largest commercial planters
cultivated 100 to 200 roots, whereas personal users planted approximately
10 roots. One root yielded three pounds of marketable ganja, which was
worth $20 to $60. Such figures were inadequate for determining the amounts
of ganja produced in the community either for local consumption or for
outside sale. The report stated: "... none of the ganja cultivators
relies exclusively on this production for a livelihood ... For the great
majority, it is an inseparable ingredient of the ganja complex style
of life, as well as a source of additional income. Cultivation of ganja
is a poor man's enterprise" (
, p. 42).
Ganja grew like
a weed and required special care only during the first three weeks after
planting. Although two crops a year were possible, most farmers planted
one. After reaping, ganja was left in the fields for several months
to dry in the sun, a process which is called "curing". Because ganja
is illegal, cultivation was done in secret by individuals. This was
unusual for Jamaican farmers who generally worked in "reciprocal partnership"
( , p. 43). Each grower of
ganja not only did all the work, but also took all the profit of a cash
crop which, unlike others had a stable price structure. Only" ... the
largest planter in the community ... employs several adolescent boys
to weed ganja fields, and pays them not in cash but with ganja" (
, p. 43).
A major problem
of the small ganja grower was protecting himself against theft, especially
when his crop lay in the field for curing. There was obviously no recourse
to the law. Unless ordered to do so, however, local police rarely disrupted
ganja cultivation. An East Indian observer in the community described
the situation:" ... poor Afro-Jamaicans fight among themselves, report
each other to the police and steal from each other's ganja plots" (
, p. 45).
In contrast to
the haphazard cultivation described above was an example of a family
enterprise from another parish. Related males worked together, cultivated
several acres, organized close watches over their crops, and maintained
elaborate warning systems against police raids. With the rising demand
for ganja export, such systems were more efficient and common.
of ganja in the community was described as "a small business activity
of a large number of occasional and part-time vendors" (
, p. 45) and as "another supplementary enterprise available to the poor"
( , p. 46). Among the 178
men covered by the study, 16 sold ganja in the community, in addition
to the five commercial producers. All 16 vendors were also consumers,
and 12 of them cultivated ganja on a small scale and sold it in small
quantities to trusted clients, friends and acquaintances. Those part-time
vendors combined selling of ganja with other work, although for some,
dealing in ganja might have provided the major part of their income.
Such dealers belonged to the lowest economic group; they had families
and stable households. Although inactive in church and community organizations,
with the exception of two "bad boys" out of 16, they were "nice guys,
jocular and inoffensive" (
, p. 46). Two of the vendors catered exclusively to the young. One of
them offered a free supply and "invites boys to share a chillum
... he has gained control of almost all the smoking sessions of the
young" ( , p. 47).
Besides those who
sold ganja to only 10 or 20 regular clients, there were large-scale
distributors who served between 50 and 100 people and held "herb camps
or yards", gathering places where clients could find, in addition to
ganja, liquor and other amenities such as television sets or record
players ( , p. 52).
To describe the
ganja trade, Rubin and Comitas depended primarily on anecdotal reports.
These reports were no substitute for data such as the amount of ganja
transacted, number and frequency of transactions, money involved and
mode of payment. Such information was unavailable and so were detailed
surveys of the village topography, land tenure, production cycles, labour
and its distribution, and size and price of different crops in relation
During the course
of their study, the investigators found no evidence suggesting the existence
of local or national organizations seeking to control the cultivation
and distribution of ganja, although Jamaica had already become a major
exporter of this drug both to the United Kingdom and the United States.
The smuggling of ganja in exchange for money and arms was soon to follow,
ending with the billion dollar illegal ganja enterprise of the 1980s.
Nothing in the report on the study foresaw such an outcome.
A community that
was typical for the area of the Blue Mountains was studied. The community
consisted of 85 households and approximately 70 per cent of its land
was under cultivation ( ,
p. 64). The investigators concluded that "no firm conclusion can be
drawn concerning the relationship between land exploitation patterns
and smoking ganja" ( , p.
79). In ten households, none of the owners were heavy ganja smokers,
while three were light to moderate smokers (
, p. 78), and land was cultivated to capacity by the owner: in six households,
the owners were able to hire labourers and in one the owner was a dealer
for whom others did most of the work. For 27 households, available lands
were only partially cultivated: in 20 households, the farmers were either
sick, too old, or pursued other occupations, while in three households
they were alcoholics and in four heavy ganja smokers. In the remaining
48 households, which possessed limited land holdings, seven were headed
by heavy ganja smokers, four of whom preferred odd jobs to farming.
From these figures,
heavy ganja smoking, like alcoholism, appeared to be not conducive to
efficient land exploitation. The authors of the report did not draw
this same conclusion however, because "these are correlative conditions"
( , p. 78).
examined four volunteers using special equipment to measure the energy
requirements and amount of motion expended during work periods. The
results indicated that, when under the influence of ganja, the volunteers
expended 50 to 60 per cent more calories, made more useless limb motions
and took up to twice as long to cultivate their fields than they would
have taken had they not smoked ganja. The farmers claimed that smoking
ganja inspired them to work harder and made them feel stronger. Although
ganja smoking actually diminished productivity, nonetheless the field-hand
not only felt good but had the impression that he was working more effectively
( , p. 70).
The increased energy
expenditure associated with the recorded decrease in productivity had
to be compensated for by a parallel increase in food intake. The report
stated "figures for average food consumption indicate that men in the
community, smokers and non smokers, eat enough to meet their energy
requirements", but added in a footnote: "data for women and children
indicate that the health of the adult males is maintained at considerable
nutritional expense to other household members" (
, p. 77). Where food was in short supply, the entire community suffered
when ganja-smoking farmers were less productive and ate up to twice
as much food as non-smokers in order to meet their caloric output. Rubin
and Comitas, however, did not point out that negative effect on the
livelihood of the community. Their opinion was that the decrease of
total cultivated area was helpful because it "limits the disruptive
effects of competition for scarce resources and market outlets and [maintains]
social cohesiveness among farmers" (
, p. 79).
that ganja is beneficial is universally held by the using population
in Jamaica and is fundamental to the belief that supports the ganja
complex" ( , p. 55). "Most
respondents associated the use of ganja with clear thinking, meditation
and concentration, ... and self-assertiveness" (
, p. 56). Subjects claimed that ganja developed their sense of responsibility,
helped them learn a trade, solve problems, design furniture, and discover
the truth. "Informants categorically stated that ganja ... enabled them
to work harder, faster and longer" (
, p. 56). Thus, "in all Jamaican settings observed, the workers are
motivated to carry out difficult tasks with no decrease in heavy physical
exertion, and their perception of increased output is a significant
factor in bolstering their motivation to work" (
, p. 79).
In their chapter
entitled "Acute effects of ganja smoking in a natural setting", Rubin
and Comitas indicated that heavy marijuana smoking decreased the amount
of work performed while it increased energy expenditure. As a result
there was a decrease in productivity (
, p. 75). They minimized their quantitative data, in claiming that the
decrease in work performance was actually beneficial to the farmers
because ganja use "supports the status quo, psychologically as well
as structurally" ( , p. 150).
The researchers appeared to attach more weight to the perceived redeeming
effects of ganja smoking, as expressed by the users, than they did to
the actual data they collected in the field.
In another report
 , Comitas claimed that cannabis
smokers cut as much sugar-cane as did non-smokers, and thereby contradicted
his earlier findings. In the latter study, however, there were no data
concerning the amount or frequency of ganja smoked and no figures for
energy consumption of the two groups. Comitas concluded that "heavy
cannabis use does not adversely affect productivity". It is a fact,
nevertheless, that Jamaican production of sugar has declined rapidly
in the decade following the study.
From a psychopharmacological
point of view, the "motivational syndrome" observed by Comitas can be
attributed to drug-oriented behaviour and drug dependence. Users need
the drug to "motivate" them to perform their daily tasks. Chopra in
India and Soueif in Egypt reported similar behaviour. Chopra stated:
"Laborers who have to do hard physical work use cannabis to alleviate
the sense of fatigue. Cannabis induces mild stimulation that enables
the worker to bear the strain and monotony of daily life". Unlike Rubin
and Comitas, Chopra did not believe in a "motivational'' effect of the
drug. According to his observations, cannabis use actually leads to
mental and physical deterioration 
. In his study comparing 850 cannabis users to 839 controls, Soueif
concluded "that the work capacity of the hashish users is significantly
impaired as to quality and quantity" 
. Soueif also noted that when the users were deprived of the drug, they
worked in an erratic fashion. The life of a chronic cannabis user became
centred around the drug which gave him a primary reward unattainable
by other means. Under its influence he submitted willingly to the drudgery
of menial tasks. In Jamaica, landowners have exploited the workers'
craving for ganja by paying part of their wages with the drug.
Two "matched" groups
of 30 ganja smokers and 30 controls recruited from the communities surveyed
made up the sample selected for clinical studies. Aged between 23 and
53 with the average age of 34 years, they all belonged to the lower
income group and had completed four to five years of school. Controls
were more likely to have held some skilled jobs and were less likely
to have suffered unemployment. Six of the smokers, or 20 per cent of
the sample, were ganja vendors. Eight of the smokers, or 26 per cent
of the sample, were Rastafarians, who constituted 2 to 3 per cent of
the Jamaican population. The authors recognized that "the sample is
non random and ... no statistical claim is made as to its representativeness
of the total population" (
, p. 181).
The smoking of
ganja was so prevalent in the lower classes that only 12 subjects in
the non-smoking control group were able to assert that they had never
smoked cannabis. Of the non-smokers 18 had in the past smoked ganja,
and eight of them admitted to being current occasional users (two or
three times a week) ( , p.
115). Furthermore, Rubin and Comitas admitted that the controls might
also have used the commonly consumed ganja-containing teas or tonics,
but "information on this subject was not collected from them" (
, p. 84). There is no certainty that any of the controls was completely
was how to determine the actual amount of cannabis smoked and for what
duration. Some smokers claimed to have smoked a minimum of three spliffs
a day for 10 years ( , p.
81). "After entering the hospital for study, two smokers admitted that
they had smoked for seven years only" (
, p. 81), and one in the group of heavy smokers in reality smoked only
a few times a week ( , p.
115). The average years of smoking was 17.5. The age at onset of regular
use ranged from 7 to 37 years with the average age at 15. The authors
stated that "an early experience with ganja may be considered predictive
of later use" ( , p. 83).
Smokers were divided
into three groups: low users with four or less spliffs a day; moderate
users with five to eight spliffs; and heavy users with more than eight
spliffs. Ganja smokers who smoked a pipe consumed from 1 to 25 pipeloads
per week. Smokers also drank ganja tea and tonics. There was no attempt
at quantifying the amount of daily use in terms of grams of cannabis
and THC equivalent. Such a quantification would have been difficult,
since a "spliff may contain anywhere from two to six grams of cannabis"
( , p. 46). The content of
samples given to the researchers for analysis varied from 0.7 to 10.5
percent with a mean of 2.8 percent of THC. The smokers were, therefore,
exposed to a wide range of THC concentration. In this respect, the smokers
lacked homogeneity, as was true of the control group.
study, no "significant differences" between smokers and controls could
be demonstrated. The reason for this lack of difference was due to the
limited number of subjects studied and to the lack of proper controls.
Ganja and tobacco
were mixed together in the spliff, but the relative proportions of one
to the other were not given. Twenty-seven ganja smokers also smoked
tobacco versus 19 controls. The exact amount of tobacco consumption
was not mentioned. Both groups drank alcohol, but the ganja smokers
tended to drink less than the non-smokers; here again, there was no
quantification of the amount consumed by either group.
Aside from ganja,
tobacco and alcohol, the subjects did not consume any other addictive
drugs. As stated by the authors, "amphetamines and barbiturates are
virtually unknown among working class Jamaicans who rely on folk medicines
and have limited access to costly prescription or patent medicine" (
, p. 164). A small amount of heroin abuse observed in Jamaica involved
tourists. Thus the addictive drugs popular in North America were not
available in Jamaica. Yet Rubin and Comitas used the Jamaican example
to indicate that, with the exception of alcohol and tobacco, cannabis
use was not associated with the use of other psychoactive drugs.
The subjects spent
a week at the Kingston University Hospital to undergo a variety of clinical
tests. Physical examination showed that one smoker had a long history
of bronchial asthma, a condition which was known to be worsened by the
effects of cannabis smoking 
 . Rubin and Comitas stated
however, "There is nothing to suggest that this disability was in any
way related to ganja" ( ,
On the average,
smokers weighed seven pounds less than the controls. Other routine clinical
examinations, tests, and lung X-rays showed that the subjects were within
normal limits while a significant proportion (30 per cent) of both smokers
and controls showed anomalies in their electrocardiogram results.
Forced vital capacity
was a test performed on both smokers and controls to measure the maximum
column of air expelled from the lungs at full capacity during a forced
expiration. Forced expiratory volume was performed to measure the volume
of air expired from the lungs during the first one-second period of
forced expiration, and peak flow rate to measure the expiratory performance
of the lung in litres per minute. On all tests, twice as many smokers
as non-smokers had a lowered capacity.
failed to determine whether the impaired lung functions were related
to dose and duration of exposure to ganja. They did not separate the
ganja smokers according to light, moderate or heavy use, nor did they
take into account the height and weight of individual subjects. Results
of the smoker group were compared with those of non-smokers and a third
group of occasional smokers who had been recruited from non-smoking
data indicated that the ganja smokers, including occasional users, had
impaired pulmonary gas exchanges. They presented lowered partial pressure
of O 2 in arterial blood (hypoxia) to be associated with
lowered partial pressure of CO 2(pCO 2) (as a
result of hyperventilation) and increased haemoglobin content of the
Because the ganja
smokers also used tobacco either separately or mixed with ganja, Rubin
and Comitas attributed the findings indicating the impairment of lung
function to "smoking per se". However, those heavy ganja smokers
who chain-smoked spliffs could hardly smoke much in the way of tobacco
in a pure form, and no evaluation was made of the comparative amounts
of ganja and tobacco used in the mixtures inhaled by the smokers.
to the contrary, data collected by Rubin and Comitas indicated that
cannabis smoking damaged pulmonary function, but their method of analysis
prevented them from reaching such a conclusion. The investigators might
have used the methods of Tashkin and others 
whose study of a group of marijuana smokers, given the drug in a controlled
environment, showed lung impairment. These authors used conventional
scientific methods and quantified their data. They found that heavy
marijuana smoking induced a dose-related decrease in the forced expiratory
volume, which showed an increased resistance to air flow 
. Their findings supersede those of Rubin and Comitas who, on the basis
of incomplete data analysis, asserted that even heavy ganja use was
not associated with any significant impairment of lung function.
evaluation, the electroencephalogram (EEG) examination and psychological
assessments did not indicate any consistent difference between cannabis
smokers and non-smokers, neither did cytogenetic studies.
evaluation indicated that ten smokers and two non- smokers reported
past hallucinations. It was not stated whether or not the two non-smokers
belonged to the occasional smokers group who had been mixed with the
controls. This information is important since 50 percent of the hallucinations
were experienced when the subjects smoked for the first time. The families
of eight of the smokers and two of the non-smokers had a history of
mental illness and seven of the smokers and three of the non-smokers
had a family history of alcoholism. One smoker was hospitalized for
a schizophrenic-type illness, perhaps provoked by heavy ganja use, and
one non-smoker had a personal history of past mental illness. In view
of the long association between cannabis use and mental illness reported
in Jamaica and elsewhere, the foregoing points should have been explored
further. Native Jamaican psychiatrists have reported instances of psychoses
induced by heavy ganja use, for example, F. Knight, whose observations
were made at the time the report by Rubin and Comitas was released 
The EEG examination
showed that 14 of the smokers and nine of the control group had low
voltage tracings, and five of the smokers (I 6 per cent) and three of
the control (10 percent) had abnormal tracings. Such results indicated
that the entire sample selected fell outside the norm of a healthy population.
The authors did not indicate whether or not the low-voltage EEG or abnormal
tracings in non-smokers were observed in occasional users. Again the
authors failed to consider a possible dose-effect relationship in analyzing
from the psychological assessment tests indicated that "long-term cannabis
use did not produce demonstrable intellectual or ability deficits" (
, p. 118). Other studies (
and  ), in which the criteria
for cannabis use and abstention were stricter and tests were performed
on larger samples, did not agree with such a conclusion. Furthermore,
conventional psychological tests are often inadequate in determining
deficits in performance which in real life are, nonetheless, apparent
to the clinical observer.
did not show any significant differences in chromosomal anomalies between
smokers and controls. However, these studies were flawed with methodological
problems: nearly half of the cell cultures did not grow and the number
of cells examined in metaphase in each preparation was too limited for
proper statistical evaluation. More recent controlled studies by Morishima
and others  on chronic heavy
marijuana users indicate that while cannabis derivatives are not clastogens,
they are mitotic disrupters (induce chromosome segregational errors).
and Comitas attributed to smoking per se rather than to heavy
ganja use many of the physical symptoms observed among the individuals
studied. In coming to this conclusion, the investigators ignored many
of the available studies that had documented the damaging effects of
cannabis on cell metabolism and cell division. Rubin and Comitas put
forward the thesis that ganja played an important, even redeeming role
in Jamaica. Ganja was "extraordinarily well integrated into working-class
lifestyles. Ganja serves multiple purposes that are pragmatic rather
than psychedelic! Working-class users smoke ganja to support rational
task-oriented behavior, to keep conscious, fortify health, maintain
peer group relations and enhance religious and philosophical contemplation.
They express social rather than hedonistic motivations for smoking ...
Ganja as an energizer is the primary motivation given for continued
use ... In fact, the ganja complex provides an adaptive mechanism by
which many Jamaicans cope with limited life chances in a harsh environment"
( , p. 166).
A dissenter to
the view of Rubin and Comitas is J. Hall, Chairman of the Department
of Medicine at Kingston Hospital. Studying ganja users for many years,
he observed  that:
syndrome, common among Indian laborers of the past generation who were
well-known for their ganja smoking habits, is now a well-established
present day finding among black male laborers in Jamaica ...
"Ganja has long
been regarded both by the laity and the profession as a cause of psychosis
in Jamaica. The unrivalled accumulated experience of Cooke, Royes, and
Williams, who were in recent years senior medical officers at Bellevue
Hospital in Kingston, Jamaica, fully substantiate this ...
"An incidence of
20% impotence among males who have smoked ganja for five or more years
was reported by me earlier ...
among ganja smokers and members of the Rastafari cult are a matter of
common observation in Jamaica. The apathy, the retreat from reality,
the incapacity or unwillingness for sustained concentration, and the
lifetime of drifting are best summed up in the 'amotivational syndrome'
of McGlothlin and West."
"The study of Rubin
and Comitas does not have the general support of experienced clinicians
and other workers in the field. We believe that the selection with which
the study was done was faulty and that, in regard to the reported absence
of any change in the chromosome pattern, their technique was faulty,
and that certainly as regards the statement that there was no respiratory
effect, it is unfounded" 
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