We all know the history of alcohol's prohibition, but did you know that the soda fountain also had its own prohibition? When I was writing Fix the Pumps, and detailing the effects the Pure Food & Drug Act of 1906 had on the soda fountain, I wondered what effect pulling all those drugs from circulation had on the mood of the country. I didn't dig into this aspect at the time as it didn't fit into the story line, but I always wondered. I've now decided to answer my own question and it is very interesting and may involve murder.
The "soda prohibition" wasn't a constitutional modification, like the US 18th amendment that enabled the Volstead Act, but a simple consumer protection law that required proper labeling of products, but also deemed substances like alcohol, cocaine, morphine, opium, cannabis and heroin as dangerous, effectively putting a halt to their excess use, though they were still available. This law took a lot of the kick out of soda and put a major dent in the snake oil salesmen of the time.
Change was happening before the laws were put on the books, most of this due to observations from ethical medical practitioners that cocaine and other drugs were not healthy (They Thirst for Cocaine (1902)). Coca-Cola is said to have removed most of the cocaine from their formulation by 1904, but there were dozens of other soda brands on the market, some still using cocaine in their formula and there were still no laws banning it outright.
When I started to look for clues as to how this new law effected the United States I found a startling result in the historical murder rates. The murder rate in 1903 was 1.1 murders per 100,000 people, in 1905 the rate doubled to 2.1 and in 1906 it doubled once more to 3.9 murder per 100,00 people. By 1907 it was 4.9, an almost 5 times increase in the murder rate since 1903.
For comparison in 1919, at the start of prohibition, the murder rate was 7.2 per 100k people and peaked in 1933 at 9.7 but then once alcohol was available the rate started to decrease and by 1939 it was down to 6.4 murders per 100k people.
When you look at the graph it is hard to ignore this rapid increase in murders in that 1903 to 1907 time frame. When you think about it, taking away drugs like cocaine, morphine, opium and heroin from addicts, I'm sure there was an increase in grumpiness due to withdrawal symptoms. A quick look through scientific research papers points to a significant increase in violence associated with cocaine use. Cocaine abstinence syndrome (withdrawal) is also associated with increased agitation and hostility. (Cocaine and Psychiatric Symptoms)
I haven't come across any other reasonable explanation as to why the murder rate increased so rapidly around 1906, but looking at the info, it is not too hard to draw the conclusion that a few people suffering from drug withdrawals had an increase in hostility and went off the deep-end. I'd say it is a plausible explanation, but may require deeper research to truly understand the effects of the Pure Food & Drug Act had on the population.