Meth is a powerful stimulant drug that increases brain activity. Short term effects, lasting up to 12 hours, include increased alertness, insomnia, hyperactivity, headache, decreased appetite, irritability, aggression, anxiety, nervousness, teeth grinding, convulsions and heart attack. Chronic abuse can lead to tooth decay, acne and skin sores (speed bumps), psychotic behavior, paranoia, hallucinations, rage, extreme violence, depression, fatal kidney and lung disorders and brain damage. Babies born to meth-using moms can be born addicted to meth and suffer birth defects, low birth weight, tremors and behavior disorders.

About 5.5% of 19-22 year-olds surveyed had used Ecstasy in the previous year.

In the 17th century, many people in Europe were treated for a variety of health problems with opium. In 1729, opium smoking was made illegal in China and soon the importation of opium was banned. This ban upset the British who were in charge of trading this valuable product. Opium was still smuggled into China and this caused the "Opium Wars" (1839-1842 and 1856-1860) between the British and the Chinese.

Although the root causes of drug addiction remain unclear, the new study reveals that scientists have identified a number of biological, psychological and social conditions that can help to identify whether a person will become an addict.