: "Studying drug abuse", New Brunswick 1985, p.149; Jaffre in: "British Journal of Addiction", 1987,82, p.597).Referring to our scheme, this proves that phenomenon B is statistically associated not only to phenomenon A, but also to phenomenons C (use of alcohol) and D (use of tobacco). As a consequence, the association between B and A is not valid to attribute a specific role of causality to A with respect to B. As stated by several authors, such association would simply mean that, in specific individuals, there is a generic predisposition toward the use of psychoactive substances (Cf. Canadian Commission 1973, p.736).
In fact, to formulate the hypothesis of a cause/effect ratio, the statistic figures relative to the population concerned by the phenomenon of which the effect is presumed (B = use of heroin) are scarcely relevant if they are not completed by a series of evidences connected to other aspects of the problem. For the example, the high rate of lung cancer among cigarette smokers is considered relevant only because there are laboratory tests on the toxic potentiality of the products of smoke on the lung tissues. More relevant is, instead, the statistic correlation for the phenomenon that is considered the cause (A = use of cannabis): in other words, the statistic rate of the use of heroin among the population of cannabis consumers. An evaluation of this kind is possible through the analysis of the epidemiological figures on the diffusion of the consumption of the various substances in a specific population, and in a specific period of time. If the theory of escalation were valid, an increase in the diffusion of ca
nnabis would correspond to an increase of the diffusion of heroin.
2 - STATISTIC ANALYSES
A precise analysis of the statistic correlation between the use of cannabis and the use of heroin can be formulated on the basis of the epidemiological figures on the consumption of illegal drugs in the U.S.
Such figures are (a) extremely reliable, because they come from governmental sources, (b) highly representative, because they refer to a population of 220 million people.
The first series of compared figures concerns the diffusion of the use of marijuana and of heroin in the seventies.
Number of regular marijuana consumers (NIDA figures; the definition of "regular" refers to persons who have used the substance at least once in the last month):
8 million in 1972 - 22,6 million (maximum ever) in 1979 = A 182% INCREASE
Number of heroin addicts (FBN and DEA figures) 626 thousand in 1972 - 380 thousand in 1978 = 39% REDUCTION
(figures by National Commission on Marijuana and Drug Abuse quoted from Maloff Paper p.133 see ZZPAPERS = 824,000)
The reduction in the number of heroin addicts at the end of the seventies is confirmed by the NIDA figures on the mortality trend: 1976 = 1487; 1977 = 616; 1978 = 505; 1979 (minimum ever) = 424; 1980 = 492.
NIDA Survey on the rate of the use of drugs among students of the San Mateo County:
marijuana: 15% in 1970, 23,3% in 1977 =
55% INCREASE
heroin: 1,1% in 1971, 0,8% in 1977 =
27% REDUCTION
(Cf. San Mateo County, Dept. of Public Health Welfare, 1977)
Another comparison is possible analyzing the consumption of marijuana and heroin between the end of the seventies and the years 1985-86: it is specially relevant, because it corresponds to the major anti-drug offensive of the Reagan administration.
In the eighties, the number of heroin addicts was not officially calculated in the U.S. However, we have a series of figures which have an indicative value, such as those of deaths due to overdose.
According to a NIDA documentation, the mortality connected to the use of heroin in 23 metropolitan areas monitored by the DAWN (Drug Abuse Warning Network) followed this trend:
1979:424 1981:659 1983:728 1985:1,225 1987:1,572
(Cf. NIDA: "Trends in Drug Abuse: DAWN 1976-1985, p.287 and NIDA: Statistical Series - Annual data 1987, Series I, Number 7, p.54).
There has therefore been a 188% INCREASE between 1979 and 1985. This trend has been confirmed by the Presidential Committee against AIDS, which estimated the number of intravenous drug consumers to be 1,3 million in 1988 (Cf. "US Journal of Drug and Alcohol Dependence", vol.12,n.3,p.1), which allows us to presume that heroin addicts are 800-900 thousand.
The figures relative to regular marijuana consumers are 22,6 million for 1979, 18,2 million for 1985. There is a 19,5% REDUCTION between 1981 and 1985.
For a more precise comparison, we should consider the fact that the use of heroin follows the use of cannabis after a certain period of time. A research conducted by Ball et al. in 1967 (quoted from: Kaplan: "Marijuana", New York 1970, p.261) estimated that the period of latency between the two phenomenons is, in average, two years; such evaluation has been confirmed by a more recent research by Farley et al. (Farley er al. in Beschner - Friedman : "Youth Drug Abuse, Lexington 1979, p.149-168), and corresponds to the individual testimonies gathered in the Italian context. A comparison between the figures relative to periods in which the use of cannabis precedes that of heroin by two or three years, may be useful.Regular marijuana consumers: 8 million in 1972, 15 million in 1976 = 87% INCREASE
Heroin addicts: 570,000 in 1975, 380,000 in 1978
= 33% REDUCTION
Regular marijuana consumers: 22,6 million in 1979, 18,2 million in 1975 = 19,4% REDUCTION.
Heroin-related mortality: 659 cases in 1981, 1572 in 1987 = 93% INCREASE.
This is the synthesis of the figures we have analyzed.
Period between 1972 to 1978-79: marijuana + 182% / heroin - 39%
Period between 1970-71 to 1977: marijuana + 55% / heroin - 27%
Period between 1981 to 1985: marijuana - 19,5% / heroin + 188%
Marijuana in the period 1972-76: + 87%
Heroin in the period 1975-78: - 33%
Marijuana in the period 1979-85: - 16,8%
Heroin in the period 1981-87: + 138%
It is evident that each increase in the use of marijuana corresponds (immediately and even after two-three years of latency) to a reduction in the use of heroin. On the contrary, a reduction in the use of marijuana corresponds to an increase in the use of heroin. In the light of these figures, there would be a negative correlation between the two phenomenons.
3- HYPOTHESES ON OTHER VARIABLES
It is possible that, by analysing other populations and other periods, the results may be different. This would in any case lead to the conclusion that the cause/effect ratio between the two phenomenons is not linked to the intrinsic characteristics of the relative substances, but to a series of variables connected to the psychological and social context.
One of the most important variables from this point of view is the illegality that brings together the use and the market of cannabis with those of heroin.
This hypothesis has been formulated by several researchers and authorities, among which the WHO (Cf. Boll.n.32,1965), the Canadian Governmental Commission (Cf. Canadian Commission 1972,p.308), and the Dutch sanitary authorities, which legalized cannabis as from 1976 in order to break the connection between the two markets. But a particularly relevant fact is that the same hypothesis was also formulated by the researchers that proposed the theory of the "transitory drug", on the basis of the statistic correlation:
"The regular use of marijuana (...) would make a contact with drug dealers and with the drug subculture more likely (...). Such contact in some cases leads to a familiarization with consumers of other drugs, a fact which increases the probability of using these other drugs".
(ODonnel, in Robins, op.cit.,p.149).
"A policy aimed at reducing the use of heroin should (...) at least consider the legal availability of marijuana, in order to break the connection between the two drugs".
(ODonnel - Clayton, op.cit.,p.239).
Another possible mechanism of the "passage" is linked to the symbolic function of the law: the use of soft drugs, as it is illegal, contributes to diminishing the symbolic and psychological deterrence of the law that prohibits the use of other substances (Cf. Canadian Commission 1972, p.304).
4 - THE HYPOTHESIS OF THE PASSAGE IN THE SCIENTIFIC RESEARCH
The first research that formulated the theory of the "transitory drug" was the one conducted by British researcher Paton in 1967. The method of the research was criticized by the Canadian Governmental Report (Cf. Canadian Commission 1972, p.129). The theory was also discredited by the Wootton Report of the British Government (1968), and by the US Report (Cf. National Commission 1972, p.110). In the following years the theory of the "transitory drug" disappeared from scientific literature: it is mentioned neither in the New York Academy of Science Report (Dornbush et al: "Chronic Cannabis Use", N.Y. 1975) nor in the NIDA researches (W.Pollin: "Health Consequences of Marijuana Use", Washington 1979), nor by the National Academy of Science ("Marijuana and Health", Washington 1982) nor by the Advisory Council on the Misuse of Drugs ("Report of the Expert Group on the Effects of Cannabis", London 1982).
During the eighties, the hypothesis of the "passage" was formulated on statistic bases by the above mentioned researches conducted by ODonnel-Clayton (1982) and by ODonnel (1985), and was mentioned in an article by J.Jaffe, Director of the Drug Dependency Section of the NIDA (1987), who, among other things, refers only very briefly to "transitory drugs, such as alcohol, tobacco and marijuana, the use of which generally precedes that of other drugs", without entering the question of a specific causality nor the mechanism of the phenomenon (Jaffe, op.cit.,p.597).
These authors are the only ones who have given a theoretical-scientific base to the theory of passage. Which is thus formulated in the most recent research by ODonnel:
"Marijuana is not the cause, but one of the causes of the use of heroin, and not necessarily the most important one" (ODonnel, op.cit.,p.148).
On the other hand, we have seen how the same authors agree on two fundamental points:
1) that the role of cannabis is not specific of the substance, as it is shared by alcohol and tobacco;
2) that the mechanism of the passage occurs through the market, and is thus caused by its illegality.
Giancarlo Arnao
CO.R.A. - Rome
SUMMARY
Is the use of cannabis the cause of a subsequent use of heroin?
If such were the case, the epidemiological figures on the diffusion of the two substances would show that, when the use of cannabis increases, so does the use of heroin.
The figures relative to the consumption of cannabis and heroin in the U.S. in the last 15 years prove the contrary:
in the seventies, the use of cannabis increased, while that of heroin diminished;
in the eighties, the use of cannabis diminished, while that of heroin increased.
Even the researchers who support the theory of the "transitory drug" admit that
1) among heroin consumers, a previous use of tobacco and alcohol is just as frequent as that of cannabis;
2) the only possible cause of the "passage" is the common availability of the two substances on the illegal market.
