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Average THC Content in Seized Cannabis Samples (1972 - 2008)


When assessing claims about THC content, it is important to have not only the measures of average THC content, but also the number of samples seized. Without knowing the number of samples, it is simply not possible to determine if the measure from one year is actually comparable to that from other years. Likewise, comparing across sample types is illustrative only to the extent that the number of samples is known. The importance of this is readily seen in the chart below in the data for hash oil THC content. In 2004, the potency of hash oil appears to have skyrocketed to an average of over 30 percent THC. But that is the average of only four samples. Clearly, we need to know not only what a given claim is, but also upon what the claim is actually based. As usual, when it comes to the war on drugs, what we aren't being told is much more important and useful than what we are being told.

Clearly, a wide variety of average THC measures have been made over the years, but the raw data is confounded not only by the overall number of samples tested, but also by how the samples were treated. Since THC readily degrades in the presence of heat and light, many of the early years of sample data are essentially worthless as there were no quality control procedures in place. Later data has much greater fidelity since there are, in general, a larger number of samples for a given product type, and the samples themselves were handled with standardized procedures.

Ultimately, what we need to know and still have no data for, are the highest recorded values for each type of cannabis product for each year. Everyone who was smoking cannabis back in the 1970's, and still does so today, will tell you flat out that the marijuana today is really no stronger than that from the past. That is because truly excellent cannabis products were indeed available back then. The big difference today is simply that there is wider availability of higher quality product. Stronger cannabis products aren't "more dangerous" -- they're just stronger, which means less product is required to get the same effect. It's quite similar to the range of alcohol products between beer and whiskey. Whiskey may be "10 times stronger" but the drug in question (alcohol) is still the same thing.



Average THC Content in Seized Cannabis Samples (1972 - 2008)
  Hash Oil Sinsemilla Hashish Marijuana Thai Stick Ditchweed
Year Number Avg THC % Number Avg THC % Number Avg THC % Number Avg THC % Number Avg THC % Number Avg THC %
1972 -- -- -- -- 6 0.60 34 1.23 -- -- -- --
1973 6 22.00 -- -- 11 1.00 33 0.83 -- -- -- --
1974 18 15.34 -- -- 53 0.86 113 1.34 1 0.54 -- --
1975 29 13.09 -- -- 86 2.28 149 1.05 -- -- -- --
1976 18 18.82 -- -- 52 3.28 209 1.94 -- -- -- --
1977 17 18.89 15 3.20 44 1.81 235 1.27 1 4.91 -- --
1978 9 21.31 1 6.28 51 2.15 128 1.47 1 0.82 -- --
1979 9 20.91 10 3.66 43 2.32 191 1.58 1 0.13 -- --
1980 8 16.56 26 6.33 37 2.58 120 1.24 1 0.05 6 0.26
1981 5 17.45 31 6.58 13 2.91 209 1.83 -- -- 20 0.32
1982 8 19.88 14 7.10 32 2.69 435 3.07 8 4.60 30 0.44
1983 30 21.36 17 7.87 47 5.47 1145 3.30 7 4.17 60 0.45
1984 33 16.75 36 6.67 59 5.75 1030 3.31 3 5.71 50 0.42
1985 25 15.08 52 7.28 41 6.49 1448 2.83 1 6.26 102 0.48
1986 23 16.51 32 8.43 53 2.66 1372 2.37 6 3.73 124 0.31
1987 22 13.36 43 7.93 63 2.62 1551 2.96 3 4.45 86 0.34
1988 16 8.52 98 7.62 43 3.35 1640 3.18 2 3.37 69 0.39
1989 9 11.96 86 6.95 19 7.06 1075 3.04 -- -- 104 0.29
1990 12 16.60 61 10.10 38 5.30 1108 3.24 1 0.12 78 0.33
1991 10 13.07 75 10.53 31 5.21 2149 3.09 -- -- 246 0.31
1992 22 13.85 76 8.57 61 5.35 3336 3.08 -- -- 107 0.31
1993 17 16.52 123 5.77 39 6.60 3033 3.38 -- -- 189 0.37
1994 14 11.57 104 7.49 29 4.60 3032 3.50 -- -- 136 0.38
1995 13 13.23 164 7.51 19 3.60 4430 3.73 2 4.52 149 0.41
1996 8 12.82 168 9.23 12 2.52 2148 3.87 -- -- 115 0.38
1997 10 18.20 111 11.62 31 8.92 2273 4.25 -- -- 57 0.49
1998 5 15.78 101 12.33 15 5.87 2075 4.22 -- -- 81 0.39
1999 11 16.21 136 13.38 23 4.94 2450 4.18 -- -- 59 0.37
2000 7 28.58 113 12.80 27 4.37 2928 4.67 1 3.27 69 0.35
2001 7 19.44 235 9.55 13 8.48 2398 5.02 -- -- 59 0.43
2002 5 22.51 528 11.36 16 9.12 1789 5.11 -- -- 67 0.40
2003 4 15.54 538 11.59 16 9.23 1893 4.97 -- -- 57 0.38
2004 4 31.32 731 11.91 25 18.95 1815 5.38 -- -- 53 0.34
2005 6 6.40 932 11.63 47 11.98 1964 5.25 -- -- 52 0.37
2006 3 18.74 1032 11.20 32 29.33 1770 5.58 -- -- 49 0.30
2007 18 24.85 1327 11.08 70 27.71 1635 6.11 -- -- 40 0.39
2008 12 6.54 1068 11.46 50 23.14 1102 5.81 -- -- 26 0.43

Sources: University of Mississippi, Marijuana Potency Monitoring Project*

* The Marijuana Potency Monitoring project is sponsored by the US National Institute on Drug Abuse. The sources of the numbers quoted here are as follows:
  1. ElSohly, M.A., et al "The Potency of Confiscated Marijuana, Hashish, and Hash Oil Over a Ten-Year Period," Journal of Forensic Sciences, Volume 29, No. 2, April 1984, pp. 500-514

  2. ElSohly M.A., et al "Potency Trends of delta-9 THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997, Journal of Forensic Sciences, Volume 45, No. 1, 2000, pp. 24-30

  3. ElSohly M.A. National Center for Natural Products Research, School of Pharmacy, University of Mississippi, Quarterly Report, Potency Monitoring Project, Report #104, Dec 16, 2008 - Mar 15, 2009


Definitions (All from ElSohly, et al)

Ditchweed

Fiber type cannabis grown wild in the Midwestern region of the USA.

Hashish

Hashish is composed mainly of the resin of the cannabis plant, mixed with some plant particles and shaped into a variety of forms such as balls, sticks or slabs which are very hard, dark green or brownish colored.

Hash Oil

hash oil is a liquid or semi-solid preparation which is basically a concentrated extract of the cannabis plant material.

Marijuana

Marijuana in the form of loose cannabis plant material with leaves, stems and seeds; includes cigarettes and those samples which cannot be described otherwise.

Sinsemilla

Marijuana in the form of flowering tops of the female Cannabis plant with no seeds.

Thai Stick

Cannabis in the form of leafy material tied around a small stem, a classical form produced in Thailand.


Note: By far, the greatest amount of annual marijuana eradication operations involves "ditchweed." Nobody smokes ditchweed.

Average THC content in UK samples 1975 - 1981

Claims of THC content and marijuana potency from press reporting.


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