Substance abuse is the overindulgence in and dependence of a drug or other chemical leading to effects that are detrimental to the individual's physical and mental health, or the welfare of others.

The disorder is characterized by a pattern of continued pathological use of a medication, non-medically indicated drug or toxin, that results in repeated adverse social consequences related to drug use, such as failure to meet work, family, or school obligations, interpersonal conflicts, or legal problems. There are on-going debates as to the exact distinctions between substance abuse and substance dependence, but current practice standard distinguishes between the two by defining substance dependence in terms of physiological and behavioral symptoms of substance use, and substance abuse in terms of the social consequences of substance use.

Substance abuse may lead to addiction or substance dependence. Medically, physiologic dependence requires the development of tolerance leading to withdrawal symptoms. Both abuse and dependence are distinct from addiction which involves a compulsion to continue using the substance despite the negative consequences, and may or may not involve chemical dependency. Dependence almost always implies abuse, but abuse frequently occurs without dependence, particularly when an individual first begins to abuse a substance. Dependence involves physiological processes while substance abuse reflects a complex interaction between the individual, the abused substance and society.

Drug abuse has a wide range of definitions related to taking a psychoactive drug or performance enhancing drug for a non-therapeutic or non-medical effect. All of these definitions imply a negative judgement of the drug use in question (compare with the term responsible drug use for alternative views). Some of the drugs most often associated with this term include alcohol, amphetamines, barbiturates, benzodiazepines, cocaine, methaqualone, and opium alkaloids. Use of these drugs may lead to criminal penalty in addition to possible physical, social, and psychological harm, both strongly depending on local jurisdiction.[2] Other definitions of drug abuse fall into four main categories: public health definitions, mass communication and vernacular usage, medical definitions, and political and criminal justice definitions.

An estimated 5.6% of the global population aged 15 to 64, or 185 million people, consume illicit drugs annually.

Domestic violence (also known as domestic abuse or spousal abuse) occurs when a family member, partner or ex-partner attempts to physically or psychologically dominate another. Domestic violence often refers to violence between spouses, or spousal abuse but can also include cohabitants and non-married intimate partners. Domestic violence occurs in all cultures; people of all races, ethnicities, religions, sexes and classes can be perpetrators of domestic violence. Domestic violence is perpetrated by both men and women.

Domestic violence has many forms, including physical violence, sexual abuse, emotional abuse, intimidation, economic deprivation, and threats of violence. Violence can be criminal and includes physical assault (hitting, pushing, shoving, etc.), sexual abuse (unwanted or forced sexual activity), and stalking. Although emotional, psychological and financial abuse are not criminal behaviors, they are forms of abuse and can lead to criminal violence. There are a number of dimensions including:

Mode: physical, psychological, sexual and/or social.
Frequency: on/off, occasional and chronic.
Severity: in terms of both psychological or physical harm and the need for treatment.
Transitory or permanent injury: mild, moderate, severe and up to homicide.

An important componet of domestic violence, often ignored is the realm of passive abuse, leading to violence. Passive abuse is covert, subtle and veiled. This includes victimization, procrastination, forgetfulness, ambiguity, neglect, spiritual and intellectual abuse.

Recent attention to domestic violence began in the women's movement, particularly feminism and women's rights, in the 1970s, as concern about wives being beaten by their husbands gained attention. Awareness and documentation of domestic violence differs from country to country. Estimates are that only about a third of cases of domestic violence are actually reported in the United States and the United Kingdom. According to the Centers for Disease Control, domestic violence is a serious, preventable public health problem affecting more than 32 million Americans, or more than 10% of the U.S. population.

Popular emphasis has tended to be on women as the victims of domestic violence. However, with the rise of the men's movement, and particularly masculism and men's rights, there is now advocacy for men victimized by women. In a special report on violence related injuries by the US Department of justice (in August 1997) hospital emergency room visits pertaining to domestic violence indicated that physically abused men represent just under one-sixth of the total patients admitted to hospital reporting domestic violence as the cause of their injuries (see table 7 of this report). The report highlights that significantly more men than women did not disclose the identity of their attacker.