Substance abuse, also known as drug abuse, 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: 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 (particularly alprazolam, temazepam, diazepam and clonazepam), cocaine, methaqualone, and opioids. In many cases criminal or anti-social behavior 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 with an estimated 120 million users of hard drugs such as cocaine, heroin, and other synthetic drugs.