Quick bread leavening process, agents (one or more food-grade chemicals—usually a weak acid and a weak base) are added into the dough during mixing. These agents undergo a chemical reaction to produce carbon dioxide, which increases the baked good's volume and produces a porous structure and lighter texture. Yeast breads often take hours to rise, and the resulting baked good's texture can vary greatly based on external factors such as temperature and humidity. By contrast, breads made with chemical leavening agents are relatively uniform, reliable, and quick. Usually, the resulting baked good is softer and lighter than a traditional yeast bread. Chemical
Substance abuse was the first to recognize substance abuse (including drug abuse) and substance dependence as conditions separate from substance abuse alone, bringing in social and cultural factors. The definition of dependence emphasised tolerance to drugs, and withdrawal from them as key components to diagnosis, whereas abuse was defined as "problematic use with social or occupational impairment" but without withdrawal or tolerance. In 1987, the DSM-IIIR category "psychoactive substance abuse," which includes former concepts of drug abuse is defined as "a maladaptive pattern of use indicated by...continued use despite knowledge of having a persistent or recurrent social, occupational, psychological or physical problem