Substances of various types exert effects on the body that trigger anger. If something is legal, some people tell themselves it can't harm them. But common sense tells you otherwise.
For example, cigarettes are legal, but everyone knows that nicotine is an addictive drug and that smoking leads to the untimely death of millions of people. Alcohol is legal, but when it's used in excess, it contributes to everything from domestic abuse and fatal traffic accidents, to heart attacks and liver disease. And caffeine — perhaps the most popular common-use drug of all — is certainly legal but can interfere with sleep and raise blood pressure.
One big problem is that most people don't think of common-use chemicals as "real" drugs — certainly not in the same way they think of heroin, cocaine, amphetamines, and marijuana. They consider them "safe" drugs that have no ill effects on their health and well-being. Most people don't really know the connection between the "chemistry of everyday life" and emotions such as anger.
The following so-called "harmless" chemicals, as it turns out, can lower your threshold for anger arousal in a number of ways:
Caffeine and nicotine stimulate the central nervous system, making it more reactive to environmental provocation. Translation: If your nervous system is ramped up, you'll have a harder time staying calm when that guy on the freeway cuts you off.
Alcohol, even in small quantities, can cloud or exaggerate a person's perceptions, causing an intoxicated person to misread the actions and intentions of others. Translation: If you've had too much to drink, you may think your girlfriend is flirting with that bartender when she's really just asking where the bathroom is.
Alcohol tends to make a person less inhibited (emotionally and behaviorally), allowing a person to feel and act in ways he wouldn't if he were sober. Translation: When you're sloshed, you're much more likely to lash out or throw a punch at someone you're upset with. (Bars have bouncers for a reason.)
Alcohol can affect a person's mood, especially in terms of depression, which in turn affects emotions such as sadness and anger. Translation: If you've ever ended up crying into your beer stein only moments after you were toasting your friends, it may be because the alcohol has wreaked havoc with your mood.