Abuse of popular drugs like hydrocodone or Adderall begins when the user starts to develop a tolerance for the substance, or the need to take larger amounts to achieve the same high. According to the Merck Manual, users at this stage are vulnerable to physical and psychological dependence. If the user goes without taking the drug for a certain period of time, or tries to reduce the dose, he or she may experience uncomfortable symptoms like headaches, nausea, anxiety, paranoia, muscle pain, and cravings. While the user may have some control over his or her habit, the need to seek and use the substance is becoming more compulsive. The user has started to experience negative consequences, such as physical illness, relationship conflicts, or problems at work; however, these consequences usually aren’t severe enough to motivate him or her to stop.
Abuse evolves into drug addiction when the user no longer has control over his or her use of the substance. Any attempt to quit results in withdrawal symptoms and overpowering cravings. Depending on the drug of choice, these symptoms may include
