Drugs are artificial or natural chemicals that, when they enter the body, they act on the central nervous system and cause changes that can affect behaviour, mood or perception.
Psychological dependence. Need to consume the substance to experience a state of pleasure or to avoid some emotional discomfort.
Physical dependence. The body gets used to the presence of the substance (neuroadaptation) and needs it in order to function normally. The person experiences physical discomfort in the absence of the drug.
Tolerance. An increased dose is needed the same effects that had been obtained with smaller doses.
You may experience any of the three effects, or all of them at once.
Drug withdrawal. This is the physical and psychological discomfort that occurs when someone who is dependent on drugs stops or reduces their use.
Classification of drugs. There are many ways to classify addictive substances. Depending on the country’s laws, they may be legal or illegal, per how their chemical structure corresponds to various groupings.
Routes of administration. In addition to the risk of use, there is also risk associated with how they are taken. The most common classification is according to the drug’s effects on the central nervous system.
Depressants: for example, opiates, alcohol, inhalants, benzodiazepines.
Stimulating substances: such as cocaine (and other derivatives of the coca plant), amphetamines, nicotine, xanthines.
Perception altering substances (psychodysleptics): for example, LSD, cannabis, mescaline, synthesis type drugs such as ecstasy, ketamine.
For more information visit:
Drug Abuse and Addiction
http://www.helpguide.org/articles/addiction/drug-abuse-and-addiction.htm
Drug Facts: Treatment Approaches for Drug Addiction
http://www.drugabuse.gov/publications/drugfacts/treatment-approaches-drug-addiction
UNODC - World Drug Report 2014
http://www.unodc.org/wdr2014/
Drugs of Abuse
http://www.dea.gov/pr/multimedia-library/publications/drug_of_abuse.pdf
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