Tendency to increase the dosage. Psychological and physical dependence. Drug use negatively effects user, their relationships, and society. There remain a number of unanswered questions on how drug addictions are formed. I. Nonspecific factors effecting an individual s response to a drug.
Different species respond differently to the same drug.
Drug responses can vary among various strains or races within a species. The sex of an individual can affect drug responses. Aging changes the effects produced by drugs. Diseases that affect circulation, distribution, metabolism or excretion can change the individuals response to drugs. Nutritional factors can influence drug effects.