Having a few drinks with friends on occasion doesn't cause much harm. But when you drink more than your body can metabolize in a short time, the physical effects can affect all areas, including the ability to speak clearly.
When you drink alcohol, it has physiological effects on the brain, the central nervous system and on emotions and judgment. As you consume more alcohol, your speech is noticeably affected.
Your speech becomes more open and uninhibited as you down more alcoholic drinks--it does not matter if you are drinking beer, wine or hard liquor. Speech becomes more animated. Even though you are feeling less inhibited, your system is being depressed by the alcohol.
Speech becomes slurred when you have more drinks. This is because of the depressant effect of the drug on your brain and central nervous system. It does not take much alcohol to affect your speech.
B.A.C. and Speech
According to Virginia Tech’s alcohol abuse prevention website, slurred speech begins to manifest itself at approximately 0.11 to 0.20 blood alcohol concentration. This is approaching twice the legal level of intoxication in many states.
Slurred speech is not simply the transient effect of overindulging on a one-time basis. According to the National Institute on Alcohol Abuse and Alcoholism, this effect, as well as others, takes place because of how alcohol affects the brain.