In each case, though, it is the recent neurobiological findings about marijuana that have provided the bridge between social and natural science. As always, Leo Hollister has something enlightening to add to the discussion. In his acceptance of the Oscar B. Hunter Award from the American Society for Clinical Pharmacology and Therapeutics in 1988, Hollister addressed the topic of "Psychopharmacology: The bridge between psychiatry and biology."(55)

"Two separate psychopharmacologic developments heralded this return of psychiatry to the biologic sciences. The most important was the discovery of drugs such as reserpine and chlorpromazine, which were truly effective for treating major psychiatric disorders. The second was the discovery of LSD, which indicated that extremely small amounts of an aberrant chemical could have profound mental effects. In somewhat more than three decades, psychiatric thinking has changed profoundly. No longer does one speak of schizophrenic, manic, or depressive "reactions" (the latter term implying that these abnormal mental states were reactions to life events), but rather these disorders are thought of as malfunctions of the brain determined by a genetic predisposition and mediated by biologic mechanisms involving neurotransmitters, receptors, and metabolic alterations."(56)

Some conditions are reactions to life events, and others are not. Hollister's bridge enables contemporary science to distinguish the two. Both Hollister and Kandel refer to instances where marijuana use may be explained by self-medication for depression or other psychopharmacological deficits, and in the some cases of therapeutic use of marijuana correction of neurochemical deficits in the cannabinoid receptor system may also have explanatory value. The preeminent value of the bridge between social science and biology is in its explanatory value, which reveals to us which aspects of behavior are more strongly influenced by biological variables than individual characteristics or the social environment. Hollister's bridge connects drugs to sets and settings, and allows scientists to view their work from both sides of the river of life.

Lee Robins of the Department of Psychiatry at he Washington University School of Medicine published an editorial in the January 1995 issue of the American Journal of Public Health based on Kandel's work; the editorial's title is "The Natural History of Substance Use as a Guide to Setting Drug Policy."(57) His concluding paragraph is a fitting summary of this discussion on the effects of marijuana's schedule I status on public health.

"One interesting possibility might be to simultaneously ban tobacco and legalize marijuana, as antithetical as these two acts appear at first. Such an action might result in cigarettes' and marijuana's swapping position in adolescents' progression from one drug to another. If tobacco is banned without legalizing marijuana, there is a greater risk that alcohol's domination of the drug scene will increase further, with known risks to drinkers' livers, hearts, memories, and offspring. Even if it did not achieve a diminution of alcohol's role, such a transposition of the legal status's of tobacco and marijuana should bring the public perception of which drug's are "soft" (i.e., relatively safe) and which are "hard" (i.e. relatively risky) closer to matching what we know about their relative physiological effects and addictive properties."(58)

Section 7 will return to the biological evidence that marijuana does not have sufficient enough of a dependence liability to justify schedule I status.