During all the phases of drug abuse–initiation, escalation of use, addiction, and relapse, there are sex differences. According to the National Institutes of Health, research has shown that women often use and respond to drugs differently. Women begin regularly using licit and illicit drugs at lower doses than do males. While women are just as likely as men to become addicted, women may be more likely to crave or relapse following abstinence. Men are more likely than women to use almost all types of illicit drugs–while use escalates more rapidly to addiction for women. The use of those illicit drugs is more likely to result in emergency room visits of overdose deaths for men. In addition, men have higher rates of dependence on alcohol and illicit drugs than women. Although there are differences among certain classes of abused drugs, sex differences in general, are the same for all drugs of abuse.