Effect of alcohol and marihuana on tobacco smoking.

Tobacco smoking covaried with alcohol consumption in male social drinkers over 15 days of unrestricted alcohol availability. Increased tobacco smoking was associated with alcohol consumption in occasional, moderate, and heavy smokers. Tobacco smoking was not systematically related to marihuana smoking even though both drugs were often smoked at the same time. During ten days of concurrent access to tobacco, alcohol, and marihuana, tobacco smoking continued to covary with alcohol consumption rather than with marihuana smoking. Marihuana smoking appeared to be independent of alcohol consumption patterns.