Stress is reported to be number one cause of drug abuse in the youth and often leads to relapse and further substance abuse. Substance abuse, also known as drug abuse and substance use disorder, is a patterned use of a drug in which the user consumes the substance in amounts or with methods which are harmful to themselves or others, and is a form of substance-related disorder. Widely differing definitions of drug abuse are used in public health, medical and criminal justice contexts. The exact cause of substance abuse is not clear, with theories including: from stress, a genetic disposition; learned from others - or a habit which if addiction develops, manifests as a chronic debilitating disease. Drugs most often associated with this term include: alcohol, substituted amphetamines, barbiturates, benzodiazepines (particular lyalprazolam, lorazepam, diazepam and clonazepam), cocaine, methaqualone, cannabis and opioids. In many cases criminal or anti-social behaviour occurs when the person is under the influence of a drug, and long term personality changes in individuals may occur as well. In addition to possible physical, social, and psychological harm, use of some drugs may also lead to criminal penalties, although these vary widely depending on the local jurisdiction. Substance abuse is widespread world over with an estimated 120 million users of hard drugs such as cocaine, heroin, and other synthetic drugs. In 2013 drug use disorders resulted in 127,000 deaths up from 53,000 in 1990. The highest number of deaths are from opioid use disorders at 51,000. Cocaine use disorder resulted in 4,300 deaths and amphetamine use disorder resulted in 3,800 deaths. Alcohol use disorders resulted in an additional 139,000 deaths.