Addiction is a major public health problem and millions of people die due to addiction (nicotine, alcohol, and drugs of abuse). The economic consequences of drug addiction are staggering all over the World. Although great strides have been made in understanding the nature of addiction, it is still not well understood. Drug addiction can be considered a chronic brain disease that affects neurotransmission between circuits of neurons that control behavior, emotion and cognition; character­ized by an excessive engagement in drug use, unsuccessful attempts in controlling drug intake, an increase in anxiety and emotional pain, and inaccurate beliefs about drug use [1]. It is a chronically relapsing disorder characterized by: (a) compulsion to seek and take the drug, (b) loss of control in limiting intake and (c) emergence of a negative emotional state (e.g., dysphoria, anxiety, irritability) when access to the drug is prevented.