Depending on their mode of action in the Central Nervous System (CNS), addictive substances can be categorized into suppressive substances that reduce levels of activity of the central nervous system, stimulants that increase normal CNS activity as well as hallucinogenic (causing illusions and hallucinations).

Addiction

Addiction to substances, according to the American Psychiatric Society (1994), is considered a chronic recurrent disorder characterized by continued commitment to finding the addictive substance with the presence of irresistible desire and compulsion for its intake, and the impossibility of limiting or discontinuing the use, which has no medical necessity but only negative consequences for the individual.

A person's decision to test a substance for the first time is influenced by several factors: genetic, idiosyncratic, psychological, and environmental. But once an addictive substance enters the body, it can promote a continuous search behavior by acting directly on the brain, affecting the structure and function of the brain, and causing long-lasting changes that affect the subsequent behavior of the user.

According to Leshner (1997) and Wise (2000), advances made in the last two decades in neuroscience have resulted in substance addiction being now considered a brain disease.

If, after chronic use, the use of the addictive substance is discontinued, a group of both physical and emotional symptoms appears: the deprivation syndrome.

Detoxification leads to the gradual retreat and elimination of the psycho-physiological symptoms of withdrawal syndrome. Strong deprivation symptoms resolve after a number of days depending on the type of substance while milder symptoms are maintained for a longer period of time.