There have been recent articles in medical literature linking caffeine addiction with alcoholism.
They seem to suggest that the high consumption of "energy drinks" and high consumption of alcohol are linked.
I'd suspect that the issue is that the addiction prone abuse both rather than that the overuse of one causes the overuse of the other.
Those who like their mental state altered, or those who may be genetically predisposed to becoming addicted to things, are the targets for the sellers of these products.
I doesn't matter whether the product is legal or illegal.
Alcohol probably would be banned if it were new to our society, although it is only toxic when over used - more than 4 standard drinks in 24 hours for an average male.
The Nicotine in tobacco is addictive, and big pharmacy wants users to buy their Nicotine product as gum or tablets rather than cigarettes, not stop using Nicotine.
Marijuana looked relatively harmless back in the 1970s, and perhaps it was, as the "weed"of today has been selected and grown for its higher THC content.
However, MJ does increase the incidence of psychotic episodes in the predisposed, and some studies suggest it can increase the risk of developing Schizophrenia when used by the young - under 17s that is in the studies.
The QEH recently reported a case of a man on treatment for a paranoid psychosis suffered an exacerbation of his condition after upping his coffee intake to over 20 cups a day.
They attributed this to the Dopamine enhancing effect of Caffeine.
What it seems to boil down to is that some people suffer from the over use of things which are not harmful in moderation if you are not already predisposed to be sensitive to them.
The problem is how do you protect those vulnerable people from themselves?
Banning things already integrated into our society is difficult for many reasons, but introducing new ones because some older ones are already permitted is probably not wise.