Methamphetamine Addiction:

Severe amphetamine induced depression and/or psychosis
Methamphetamine stimulates the central nervous system, causing chemical reactions in the brain and tricking the body into believing it has unlimited energy supplies and draining energy reserves needed in other parts of the body. This is why meth addicts tend to stay awake for long periods of time and then eventually crash, feeling tired, depressed and much worse than they did before they took the drug. Chemical imbalances in the brain and sleep deprivation commonly associated with continued meth use result in hallucinations, extreme paranoia and often bizarre, violent behavior.

Meth causes extensive damage to the body, and can cause death or permanent physical damage.

Physiological effects of methamphetamine use include:
Abnormally high blood pressure; rapid and irregular heart rate and rhythm; seizures; damage to blood vessels in the brain (stroke); accumulation of excess fluid in lungs, brain tissue and skull; continuous/excessive dilation of the pupils; impaired regulation of heat loss; Hyperpyrexia (body temperatures higher than 104°); internal bleeding; damage to other organs caused by disruption of blood flow; and breakdown of muscle tissue, leading to kidney failure.

Similar to other drug substances, smoking and inhaling meth damages the lungs and nasal passages, and intravenous use can lead to spread of the AIDS virus.

The drug appeals to the abuser because it increases the body's metabolism and produces euphoria, alertness, and gives the abuser a sense of increased energy. But high doses or chronic use of meth, also known as "speed," "crank," and "ice," increases nervousness, irritability, and paranoia.