The Marijuana Policy Project notes a new study of pot smokers in San Francisco and Amsterdam that finds patterns of marijuana use in the two cities are similar despite substantial differences in drug policies. The Dutch government tolerates the open retail sale of marijuana to adults, which in the U.S. remains completely illegal. "Despite widespread lawful availability of cannabis in Amsterdam," the authors write, "there were no differences between the two cities in age at onset of use, age at first regular use, or age at the start of maximum use….We also found consistent similarities in patterns of use across the different policy contexts."
One significant difference between the two cities was that marijuana users in San Francisco were more likely to use MDMA (Ecstasy), cocaine, amphetamines, and opiates. "Dutch decriminalization does not appear to be associated with greater use of other drugs," the researchers report. "Indeed, to judge from the lifetime prevalence of other illicit drug use, the reverse may be the case."