American Marijuana Potency:
Data Versus Conventional Wisdom (Unpublished speech)

by John P. Morgan, M.D.
Department of Pharmacology
City University of New York Medical School

Introduction

On June 6, 1990, in a televised debate on marijuana
decriminalization, Dr. Arnold Washton (known chiefly for the treatment of
cocaine users) stated that new forms of marijuana were so potent that they
could not be viewed in the same context of relative safety as in the past.
Further media presentation of the potency argument in 1990 occurred
with a description of a "10-15 fold recent increase in marijuana potency"
in a televised debate on November 6, 1990, on a Fox television early
morning news show by a former DEA agent now offering her services as a
consultant to industry on substance abuse policy.
By 1990, I had become critical of such claims, but I had once
accepted them. In the Merck Manual, a widely distributed general medical
textbook, I wrote in 1982, "The content of THC in American marijuana has
increased."
The year 1990 actually marks a decade of claims describing
remarkable increases in marijuana available in North America.

Potency Claims in 1980

In May of 1980, Jane Brody wrote about marijuana in the New York
Times. She interviewed Dr. Sidney Cohen and Dr. Robert DuPont (both
former heads of the National Institute on Drug Abuse, NIDA). These experts
were:

"....disturbed about the rapidly increasing potency of the
marijuana generally available to Americans. In 1975, the average sample of
confiscated marijuana contained 0.4% of the mind altering chemical, THC.
By last year, because of improved cultivation practices, the average was 4
percent of the active drug -- a tenfold increase in potency."

Although neither Brody nor her informants refer to it, they may
well have known of Marijuana and Health, the Eighth Annual Report of the
Secretary of HEW to the U.S. Congress. In fact, Dr. Sidney Cohen was an
informant to Dr. Robert C. Petersen who wrote this document. The executive
summary of Marijuana and Health states:

"Street marijuana has increased markedly in potency over the last
five years. Confiscated materials in 1975 rarely exceeded one percent THC
content. By 1980, samples as high as five percent THC content were
common."

Dr. Petersen was a NIDA employee. This informal report may have
been very important in the spread of the "new" marijuana argument of the
1980's. Baker and his colleagues described the THC content of imported
marijuana samples seized in Britain and identified as to origin. Although
the few American samples did not show any particular trend, the British
scientists repeated the claim of a remarkable increase in American
marijuana potency and cited only Petersen's report. Unfortunately, they
were influenced more by the certainty of his executive summary than the
caution of his inner text.
In 1984, another important policymaker contributed to the
description of the new marijuana. Donald I. MacDonald, then a pediatrician
in Tampa, Florida, wrote a book entitled 'Drugs, Drinking and Adolescents.'
The ideas in this book contributed to MacDonald's ascension to Director of
the White House Office of Drug Policy in the Reagan administration. He
presented detailed claims about marijuana potency, tabulating these numbers
for THC concentration:

1965 - 0.1% - 0.2%
1970 - 1%
1983 - 2 -- 4%

He listed 1975 testimony before Congress as the source for these
data but also referred to a University of Mississippi potency monitoring
project. (Petersen had also referred to studies at Mississippi).
MacDonald discusses the striking advances in horticulture that have
generated these new strains. He describes hybridization of the North
American plant with a potent Asian variety and a fast-growing variety from
the Soviet Union. Also, "The whole horticultural business is very
complicated, incorporating much sophisticated and advanced technology." He
does not cite references or documenting articles about this horticultural
revolution.
Parenthetically, I'm unaware of any measure of the delta-9-THC
content of the plants prior to 1968, and only a few plants were assayed
before 1972. The decision that measurement of the weight of delta-9-THC
might reflect the potency of marijuana was actually accepted only after
1965.
In 1986, Dr. Sidney Cohen returned prominently to the issue of
potency in his newsletter on alcohol and drug abuse.

"....[M]aterial ten times or more potent than the product smoked 10
years ago is being used and the intoxicated state is more intense and lasts
longer...a glance at the percentages of THC in confiscated marijuana would
indicate that marijuana is now as strong as hashish in THC content."

Also in 1986, Cohen was interviewed by Miles Corwin for an article
published in the 'Los Angeles Times.' Cohen stated that as a result of
sophisticated growing techniques, the average content of THC in top-grade
marijuana is about 7% and can be as high as 14%. This contrasted with
average THC content in marijuana bought on the street only 10 years before
which had a THC content of less than 1%. Cohen said:

"A lot of the stuff on the streets is now more than 10 times
stronger than what people had been used to; it's almost a completely
different drug.
Corwin also interviewed Darryl Inaba from the Haight-Asbury Drug
Clinic in San Francisco who noted that potent California marijuana became
prevalent in the early 1980's and began to cause anxiety reactions. He
compared these reactions to the bad trips of LSD in previous years.
Inaba, in a 1987 publication, also described a heretofore
unrecognized outcome of the use of the new potent marijuana.

"This new stronger marijuana has a more disruptive effect on brain
chemistry and body physiology than we had imagined previously. Baseball
players who get beaned a lot admit to smoking marijuana. It impairs their
ability to follow the ball."

Cohen died in 1986 and his statements on the new marijuana were
adjudged part of his legacy. D.E. Smith, in homage, stated that Cohen:

"....taught us that marijuana was a lot more dangerous than we
originally thought, particularly with the use of more potent preparations
by young people."

In September of 1986, the new potency of marijuana again reached
the fron page of the 'New York Times.' This time another NIDA staff
scientist Dr. Robert Hawks outlined the increasingly familiar scenario to a
newspaper reporter:

"....[S]tudies conducted for the National Institute on Drug
Abuse....by the University of Mississippi....has (sic) shown a rise in the
psychoactive agent in marijuana, THC, from an average of 0.5 percent in
1974 to 3.5 percent in 1985 and 1986."

Peter Kerr, author of the 1986 'New York Times' article, did not
note that Brody's 1980 'New York Times' article had described a 4.0% THC
content and he therefore did not discuss an apparent decline in marijuana
potency of 12.5 percent between 1980 and 1986.
Before I turn to an analysis of the University of Mississippi data
(there are some), I would like to trace further the story of marijuana
potency in American newspapers during the decade of the 1980's.

MARIJUANA HORTIULTURE AND NEWSPRINT

The marijuana plant was once the major source for American
newsprint. In the 1980's newsprint was the source for a series of
speculative beliefs about the astonishing skills of domestic growers of
marijuana in addition to the 'New York Times' and 'LA Times' articles
already mentioned.
Mosley, writing in the 'St. Louis Dispatch' in 1989, describes the
amazing new marijuana and lists one reason for it. He interviewed Ray
Rothenberger, Chairman of the Department of Horticulture at the University
of Missouri, Columbia who noted that marijuana potency would benefit from
the bountiful summer rain. Referrring to marijuana, Rothenberger said,
"It thrives in hot, wet weather. With plenty of moisture, the plants
become larger and more productive."
Perhaps the science (or art) of cannabis botany is illuminated by
another comment one year earlier in an Associated Press article datelined
Charleston, West Virginia. There, a reporter learned from the State
Agricultural Commissioner that the hot, dry weather was increasing potency.
Gus R. Douglas said that the marijuana plants are stunted but that the
enzymes (sic) that produce a high are more concentrated.

"When you get hot, dry weather like this, it does improve the
quality of the marijuana. It could be a more potent crop out there."

Other American newspaper articles of the 1980's read as if they
were generated by press releases from lthe Amalgamated Marijuana Growers of
America, if such a trade organization had existed. The articles positively
gushed about the fantastically potent marijuana now grown in the United
States. Spokesmen often assumed a parochial tone of pride while discussing
the high quality in their local region.
Sometimes those describing lush crops, were pro-marijuana activists
from NORML, although usually the law enforcement community congratulated
the horticulturists.
"I hate to sound laudatory," says W. Michael Aldridge of the DEA,
"but the work they've done on this plant is incredible." Another DEA agent
said, "We are now producing the best marijuana in the world and that is
one of the reasons it's becoming so popular."

SINSEMILLA AND OTHER TECHNIQUES

Most of these reporters believed that the "sinsemilla" technique
in which male plants are removed early from a crop to induce the female
plant to make more THC was recently discovered in the United States. A
deputy sheriff in Meigs County, Ohio, Jim Soulsby, believed that sinsemilla
began with some experiments at nearby Ohio University. Mikurya and
Aldrich, in a detailed article about marijuana potency and its early use
and cultivation, confirm that the sinsemilla technique is at least 100
years old. American reporters accepted uncritically that the productionof
sinsemilla is relatively easy and the usual practice in the industry. In
an article to which I'll return, the growers of approved standard marijuana
for research in Mississippi point out that removal of the male plant at the
proper time is difficult and one full-time worker is required for every 24
plants. Even the successfully culled plot containing only female plants
may be pollinated by wind blown material from male plants in the immediate
and not so immediate vicinity. Indeed, the production of sinsemilla in
volume must be difficult or it would make up a larger volume of seized
plants than it does now.
American reporters resort to jargon to describe revolutionary
horticultural techniques. Frequently, local agricultural experts are
quizzed, but just as often, no particular source is cited for botanical
techniques. Two typical examples:

"In keeping with the American tradition of agricultural tinkering,
domestic growers in the 1980s began experimenting with new seed varieties,
improved hybrids and cloning to make plants grow smaller for indoor
operations -- while yielding new marijuana of higher potency.

Breeding, cloning, seed selection hydroponics and growing
techniques that isolate the especially potent, unpollinated female
plants....have produced a homegrown product with off-the-chart
concentrations of pot's psychoactive ingredient...."

Cloning in gardening merely refers to starting a new plant with a
cutting from an existing plant. These reporters may have believed that it
actually referred to growing a plant from a single cell.

DR. MAMOUD ELSOHLY AND THE POTENCY MONITORING PROJECT

Although most references to marijuana potency increases are
undocumented, the existing citations refer to a potency assessment project
based at the University of Mississippi at Oxford. This project based at
the University of Missisippi at Oxford. This project publishes quarterly
reports which are not widely distributed. Indeed, there is no mailing list
for the NIDA-sponsored project reports but they are widely available (from
Robert L. Walsh, Research Technology Branch, NIDA, Room 10A-13, 5600
Fishers Lane, Rockville, MD 20857). Much of the data presented below come
from Quarterly Report #32 which reports all samples analyzed through 1989.
Each Quarterly report is cumulative and records earlier findings.
Mahmoud ElSohly, who is trained as a pharmacist and medicinal
chemist, has long directed the project. In an interview with the
Associated Press in 1986, he indicated that the Mississippi Project was the
source of Hawks' data given to the 'New York Times.' He stated that the
Institute which tests samples of marijuana seized by law enforcement showed
that the average content of tetrahydrocannabinol, the active ingredient in
marijuana, has risen from 0.5% in 1974 to 3.5% in 1984. "Smoking one
marijuana cigarette now is equivalent to smoking seven marijuana cigarettes
nine or ten years ago."
ElSohly also engages in an unusual unproved speculation. He
believes that marijuana has become more potent in the last 12 years to
satisfy users who have developed a tolerance to it. "It just means that
the people are getting more addicted so they need more of the active
ingredients just like any other drug."
There has been one publication in the archival literature
describing the Mississippi Monitoring Project in some detail. In this
paper, ElSohly reviewed the findings up to 1981 and also carefully
characterized the samples.

THE POTENCY MONITORING PROJECT'S CHARACTERISTICS

NIDA and the DEA agreed in 1975 that all DEA seizures greater than
200 pounds (90 kilograms) would be sampled and assayed (recently the
required weight has apparently decreased to 75 kgs). In addition to DEA
samples, essentially all of which represented border seizures, the project
later sampled and assayed material seized by state police departments.
Thewse represent domestic marijuaa in contrast to the DEA samples which
represent imported marijuana. In recent years, the percentage of total
samples made up of domestic material has grown considerably although this
expansion did not begin until 1980. Prior to 1980 the percentage of
domestic plants inclueded in any of the annual smples was less than 9.1%.
The project has also always characterized plant material as to
format. The most common versions are: marijuana (loose cannabis plant
material); kilobrick (cannabis compressed into a brick form, essentially
always of Mexican origin); buds (flowering tops of cannabis with seeds);
sinsemilla (flowering tops without seeds).
Samples are examined for cannabinoids other than delta-9-THC.
Cannabinol and cannabidiol are also measured and reported as annual mean
concentrations. Cannabinol in all probability results from degradation of
delta-9-THC; degradation that occurs over time of storage of dry plant
material particularly at increased ambient temperatures. The concentration
of cannabinol then is a rough indicator of improper storage -- a problem
commented on by ElSohly et al. in the 1984 publication.
In interviews, ElSohly refers to the project as monitoring
marijuana potency since 1968. As noted, the funded project began in 1975
and the reported analyses usually begin with 1974. However, some
tabulations include seizures analyzed before 1974 or 1976 depending on the
table. In the Journal of Forensic Sciences report, the assays go back to
1972, although some mean calculations apparently use samples seized before
1972. Despite these extensions, the information in any quarterly report is
extremely sketchy prior to 1974.

MISSISSIPPI POTENCY MONITORING PROJECT

Quarterly report #32 lists all analyses through 1989. It includes
normalized and non-normalized annua. The Cohen comparisons of 1980 are
particularly deceptive. He used the 0.4% of the 1974 data but compared it
to a 4.0%, approximating the concentration only of domestic material seized
since 1980. This comparison to 1974 and 1975 obviously generated directly
or indirectly most of the reports and comments by Petersen, MacDonald,
DuPont, Cohen and Hawks about the massive increases in marijuana potency
accepted as revealed truth by American newspapers.
ElSohly is so convinced by these comparisons that he testified
about them in 1987 in a Federal court. He was a government witness
opposing a lawsuit claiming that marijuana should be reclassifies as a
Schedult II drug, reflecting its utility as a medication.

"Under the NIDA contract, we have been analyzing confiscatied
marijuana samples to determine their potency in terms of the concentration
of THC. We have seen an increase in the average potency of these materials
over the uears. In the early 1970's the average potency was less than 1%
and the maximum average potency reached in 1984 was approximately 4%."

THE 1974 -- 1975 SAMPLES

Dr. ElSohly and his cited commentators then all base their beliefs
on this series of assays which initially analyzed a few seized imported
samples mailed by the DEA to Oxford, Mississippi. How representative of
the marijuana in use in the early 1970s were these samples? More
specifically:

1) What were ltheir origins -- from where did they come?
2) How well were they stored and preserved -- what was their
cannabinol content?
3) What type of cannabis plant material made up these samples --
for example, how many sinsemilla samples were in these early samples?
4) Were there other analyses of marijuana plants conducted
elsewhere in the early 1970s. In summary, do these early
samples reflect properly a larger universe of available
American cannabis material in the early 1970s?

THE MISSISSIPPI SAMPLES OF THE 1970s -- MEXICAN KILOBRICKS

ElSohly's only peer-reviewed discussion of the project is
conservatie in his claims and generalizations. Prior to 1972, there were
only 65 samples examined and few of these came from the main sources of
later years -- DEA and state seizures. In 1974, the number of samples only
exceeded 100 for the first time, but none of these 114 samples in 1974 were
of domestic origin. Most of the imported samples of 1974 and 1975 were of
Mexican origin packaged as compressed plant material (kilobricks). Not
all imported marijuana plant material is of low potency but Mexican
kilobricks of the early 1970s surely were. In 1974 and 1975, the
delta-9-THC concentrations in the kilobricks were 0.40% and 0.47%
respectively. The percentage of all samples made up of this Mexican
material was approximately 50 and 60% in the same two years. In 1975,
kilobrick samples numbered 88 while loose plant marijuana samples numbered
only 58. The calculation used to generate the 0.4 and 0.5% potencies also
employed normalized statistics in which the relatively high weight of the
kilobrick seizures was factored in and yielded the lowest average
concentration of THC. In fact, even using the Mississippi data, the
arithmetic mean concentration of delta-9-THC in 1974 and 1975 was
approximately 1%. Mikurya and Aldrich believe that sinsemilla agriculture
was well understood in California in the 1970s and had made a contribution
to the average THC concentration of commercial marijuana by that time. The
Mississippi Project analyzed no sinsemilla samples in 1974-1976 and did not
exceed 15 samples until 1980.

CANNABINOL CONTENT

It is accepted that delta-9-THC degrades to cannabinol in dry plant
material on storage and particularly in high-temperature storage. Mikuriya
and Aldrich speculated that some material assayed in NIDA programs of the
early 70s might have been badly stored and lost delta-9-THC in police
locker rooms and other evidence storage sites. ElSohly's 1984 paper
confirms this. Referring to the 1972-1981 data:

"....the [tabulation] shows significantly high concentrations of
CBN indicating either old plant material or poor storage conditions."

If we examine the arithmetic mean of cannabinol percentage in 1974,
and 1975, it is .49 and .55 respectively. Although all Mississippi
measures have a high percentage of CBN, 1974 and 1975 plants were generally
the highest. Of all the 16 years of data only 1978 estimates (cannabinol
concentration .67%) exceed the 1974 and 1975 years. Freshly harvest
meaterial generally has a concentration of .02% Adapting the style of the
reporters of potency, I could say that the 1975 samples show a
concentration of degradation product 27.5 times that of fresh marijuana.

DOMESTIC SEIZURES

As previously noted, after 1980, domestic material began to
constitute a significant percentage of the Mississippi samples and now most
samples are domestic. Data from lthe last quarterly report of the
Mississippi Project confirms that there has been no change in the
delta-9-THC content of seized domestic marijuana since 1981.

SINSEMILLA

The percentage THC of the sinsemilla has remained relatively
unchanged since 1981 and there is no particular pattern or evidence of
increased sinsemilla production reflected in these seizures. The
percentage of domestic seizures made up of sinsemilla was higher in 1981
(23%) than anytime from 1982-1989.

OTHER MARIJUANA ASSAYS OF THE 1970s

There are few surveys of cannabis potency available in the 1970s
and some of them may have similar problems to the Mississippi Project.
However, there are no surveys indicating an average potency of 0.4 or 0.5%.
In 1973, the 'PharmChem Newsletter' reported 49 samples sent to ehm
anonymously for analysis. The average THC concentration of these
uncharacterized plants was 1.62% compared to a .27% concentration of
delta-9-THC in 27 samples sent to Mississippi in 1973. Most of these
Mississippi samples were DEA seizures of Mexican loose plant material.
In 1979, Ritzlin et al. reviewed the experience of a street
identification project which also received samples anonymously for
identification. Between 1974 and 1977, they analyzed 38 marijuana products
and discovered a mean THC content of 7.0%. In 1974 they inspected only 9
samples, but the average THC concentration was 4.*%. Some of this material
was characterized as sinsemia (sic), California seedless and homegrown.
Both of these street lab projects were constrained by a DEA
decision to prevent the reporting of quantitative THC concentrations in
anonymous submissions. This effectively prevented the reporting of widely
sampled American material and made it easy for Hawks and Cohen and ElSohly
to rely on the distorted early Mississippi samples. However in 1977,
PharmChem did review its experience in very general terms from 1969-1975.

"Early quantitative work showed a range of 1.0-2.5% THC for average
marijuana. In 1975, the range was 2.0-5.0%;
samples in the range of 5.0 -- 10.0% were not uncommon."

Therefore in 1975, when Dr. ElSohly and his colleagues reported a
mean concentration of 0.5% THC in Oxford, Mississippi, a laboratory in
California apparently examined no samples with less than 2.0%.
Prohibition of substances usually leads to increased potency of
marketed forms. However, in the case of cannabis plant material, the
assumption that increasing concentrations of the psychoactive principle
delta-9-THC emerged over a brief time of active growing and marketing are
not true. The reasons lie probably in the conservatie nature of plants and
the poorly understood character of the botanical production of
cannabinoids. A discussion of botany is beyond me, but a quote from a
prominent source, Robert Clarke, for the botany of marijuana is
illuminating, "There is really no confirmed method of forcing increased
THC production."
In 'Marijuana Botany,' Clarke discusses heat and humidity (of the
soil and the air), exposure to light, age of plants, the encouragement of
flowering and the difficulties of sinsemilla production.
Although increased THC is the desire of growers and the belief of
marijuana critics like Cohen, DuPont, and MacDonald, there is no evidence
that twenty years of domestic marijuana cultivation has produced a
systematic increase in THC production. The chief control of the THC
production is contained in and constrained by the genetic characterof the
plant and this is no less true in 1990 than it was in 1970.


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