Popularly known as bennies, crank, speed, pep pills, wakeups, or uppers, amphetamines are addictive and easily abused: users can become psychologically dependent on the drugs and, developing a tolerance for them, can require increasingly large doses (see drug addiction and drug abuse). When the drugs wear off, a long period of sleep ensues, often followed by hunger and depression, which can lead to further use of amphetamines. Amphetamine addiction has been common among such diverse groups as truck drivers, students, and athletes, who have used the drugs for increased energy, alertness, or endurance. Methamphetamine, made from ephedrine and other chemicals in clandestine laboratories in the the United States or Mexico, experienced a resurgence in use in the United States beginning the mid-1990s, and its abuse also has increased worldwide. Amphetamines are inhaled, taken orally, or injected; as with other injected drugs, needle sharing increases the risk of contracting the AIDS virus. One form of methamphetamine, "ice," is smoked. For law enforcement purposes in the United States, most amphetamines are grouped with such drugs as cocaine and morphine because of the similarity in their effects, medical usefulness, and high potential for abuse.