Short answers, pulled from the story.
Addiction is a neuropsychological disorder that hijacks the brain's reward system, creating a persistent and intense urge to use a drug or engage in a behavior despite substantial harm. This phenomenon begins when repetitive drug use alters brain function in synapses, mimicking natural rewards like food or falling in love in ways that perpetuate craving and weaken self-control.
DeltaFosB is a critical gene transcription factor that serves as a common factor in the development of virtually all forms of behavioral and drug addictions. Overexpression of DeltaFosB in the D1-type medium spiny neurons of the nucleus accumbens is necessary and sufficient for many of the neural adaptations and behavioral effects seen in drug addiction.
Genetic factors account for 40 to 60% of the risk factors for alcoholism, and similar rates of heritability for other types of drug addiction have been indicated. Twin studies provide evidence that if one twin is affected by addiction, the other twin is likely to be as well, and to the same substance.
The ICD-11 offers three diagnostic possibilities for substance use: an episode of harmful psychoactive substance use, a harmful pattern of psychoactive substance use, and substance dependence. This framework moves away from the binary of abuse and dependence used in past editions.
The United States reported that 43.7 million people aged 12 or older needed treatment for an addiction to alcohol, nicotine, or other drugs. Only about 10% of these individuals receive any form of treatment.