498 Substance-Related and Addictive Disorders
observed at different time points. Evidence of mild intoxication with alcohol can be seen in
most individuals after approximately two drin ks (each standard drink is approximately
10–12 grams of ethanol and raises the blood alcohol concentration approximately 20 mg/
dL). Early in the drinking period, when blood alcohol levels are rising, symptoms often
include talkativeness, a sensation of well-being, and a bright, expansive mood. Later, es-
pecially when blood alcohol levels are falling,  the individual is likely to become progres-
sively more depressed,  withdrawn, and cognitively impair ed. At very high blood alcohol
levels (e.g., 200–300 mg/dL), an individual who has not developed tolerance for alcohol is
likely to fall asleep and enter a first stage of anesthesia. Higher blood alcohol levels (e.g., in
excess of 300–400 mg/dL) can cause inhibition of respiration and pulse and even death in
nontolerant individuals. The duration of in toxication depends on how much alcohol was
consumed over what period of time. In general, the body is able to metabolize approxi-
mately one drink per hour, so that the blood alcohol level generally decreases at a rate of
15–20 mg/dL per hour. Signs and symptoms of in toxication are likely to be more intense
when the blood alcohol level is rising than when it is falling.
Alcohol intoxication is an important contri butor to suicidal behavior. There appears to
be an increased rate of suic idal behavior, as well as of co mpleted suicide, among persons
intoxicated by alcohol. 
Prevalence 
The large majority of alcohol consumers are likely to have been intoxicated to some degree at