Highlights•Alterations in endogenous opioid system components occur in development of
addiction.•Human studies and animal models show opioid genes contribute to addiction …

Addictions to drugs of abuse and alcohol have been shown by studies of genetic
epidemiology to have both a heritable and an environmental basis, with these factors …

Addiction to drugs is a chronic, relapsing brain disease that has major medical, social, and
economic complications. It has been established that genetic factors contribute to the …

Opium, extracted from the seed of the poppy Papaver somniferum, has been used and
abused for several thousand years. This substance is highly efficient to relieve pain or treat …

A number of dramatic breakthroughs in the neurobiology of addiction have occurred in the
past 40 years. Two domains will be highlighted: the neurocircuitry of addiction and the …

It has been estimated that more than 80% of alcoholics are also nicotine dependent and
that, vice versa, the rate of alcoholism is substantially increased by a factor of 4–10 in the …

The endogenous opioid system is expressed throughout the brain reinforcement circuitry,
and plays a major role in reward processing, mood control and the development of …

Drug addiction is a chronic brain disorder leading to complex adaptive changes within the
brain reward circuits that involve several neurotransmitters. One of the neurochemical …

Opioid addiction and overdose are at record levels in the United States. This is driven, in
part, by their widespread prescription for the treatment of pain, which also increased …

It is now well established that opiate drugs, such as heroin and morphine exert their primary
effects by mimicking naturally occurring substances, termed the opioid peptides or …