Alcohol Hangover

Direct Alcohol Effects:

Alcohol may directly contribute to a hangover in several ways, including the following.

Dehydration and Electrolyte Imbalance - Alcohol causes the body to increase urinary output (i.e., it is a diuretic). Alcohol promotes urine production by inhibiting the release of a hormone (i.e., antidiuretic hormone, or vasopressin) from the pituitary gland. In turn, reduced levels of antidiuretic hormone prevent the kidneys from reabsorbing (i.e., conserving) water and thereby increase urine production. Additional mechanisms must be at work to increase urine production, however, because antidiuretic hormone levels increase as BAC levels decline to zero during hangover. Sweating, vomiting, and diarrhea also commonly occur during a hangover, and these conditions can result in additional fluid loss and electrolyte imbalances. Symptoms of mild to moderate dehydration include thirst, weakness, dryness of mucous membranes, dizziness, and lightheadedness - all commonly observed during a hangover.

Gastrointestinal Disturbances - Alcohol directly irritates the stomach and intestines, causing inflammation of the stomach lining (i.e., gastritis) and delayed stomach emptying, especially when beverages with a high alcohol concentration (i.e., greater than 15 percent) are consumed. High levels of alcohol consumption also can produce fatty liver, an accumulation of fat compounds called triglycerides and their components (i.e., free fatty acids) in liver cells. In addition, alcohol increases the production of gastric acid as well as pancreatic and intestinal secretions. Any or all of these factors can result in the upper abdominal pain, nausea, and vomiting experienced during a hangover.

Low Blood Sugar - Several alterations in the metabolic state of the liver and other organs occur in response to the presence of alcohol in the body and can result in low blood sugar levels (i.e., low glucose levels, or hypoglycemia). Alcohol metabolism leads to fatty liver (described earlier) and a buildup of an intermediate metabolic product, lactic acid, in body fluids (i.e., lactic acidosis). Both of these effects can inhibit glucose production. Alcohol-induced hypoglycemia generally occurs after binge drinking over several days in alcoholics who have not been eating. In such a situation, prolonged alcohol consumption, coupled with poor nutritional intake, not only decreases glucose production but also exhausts the reserves of glucose stored in the liver in the form of glycogen, thereby leading to hypoglycemia. Because glucose is the primary energy source of the brain, hypoglycemia can contribute to hangover symptoms such as fatigue, weakness, and mood disturbances. Diabetics are particularly sensitive to the alcohol-induced alterations in blood glucose. However, it has not been documented whether low blood sugar concentrations contribute to hangover symptomatically.

Disruption of Sleep and Other Biological Rhythms - Although alcohol has sedative effects that can promote sleep onset, the fatigue experienced during a hangover results from alcohol's disruptive effects on sleep. Alcohol induced sleep may be of shorter duration and poorer quality because of rebound excitation after BAC's fall, leading to insomnia. Furthermore, when drinking behavior takes place in the evening or at night (as it often does), it can compete with sleep time, thereby reducing the length of time a person sleeps. Alcohol also disrupts the normal sleep pattern, decreasing the time spent in the dreaming state (i.e., rapid eye movement [REM] sleep) and increasing the time spent in deep (i.e., slow-wave) sleep. In addition, alcohol relaxes the throat muscles, resulting in increased snoring and, possibly, periodic cessation of breathing (i.e., sleep apnea).

Alcohol interferes with other biological rhythms as well, and these effects persist into the hangover period. For example, alcohol disrupts the normal 24-hour (i.e., circadian) rhythm in body temperature, inducing a body temperature that is abnormally low during intoxication and abnormally high during a hangover. Alcohol intoxication also interferes with the circadian nighttime secretion of growth hormone, which is important in bone growth and protein synthesis. In contrast, alcohol induces the release of adrenocorticotropic hormone from the pituitary gland, which in turn stimulates the release of cortisol, a hormone that plays a role in carbohydrate metabolism and stress response; alcohol thereby disrupts the normal circadian rise and fall of cortisol levels. Overall, alcohol's disruption of circadian rhythms induces a "jet lag" that is hypothesized to account for some of the deleterious effects of a hangover.