Dependence on illegal medication is called as addiction. Recreational drugs and a few prescribed drugs have the ability to caused addiction. Only a very small fraction of the population who have consumed it are able to resist addiction, while the others suffer adversely at home, work, school, relationship etc. Drugs which have the ability to cause addiction alter the dopamine levels in brain and other neurotramitters giving a positive euphoric feeling. Drug addicts create a false and illusionary world of happiness around them and will not be able to tolerate if the drug consumption is suspended.Thus, they suffer from withdrawal symptoms often craving for the drug.