The addiction may be different but the circuit in brain that compels the addicted person to reinforce the habit remains same. Addictions start small. Addiction, whether a behavioral addiction or substance abuse both, begin with small quantity and no or little intention of repeating. The substance releases dopamine in brain which produces feeling of excitement, happiness and satisfaction collectively called euphoria. This feeling is quite addictive and the person wants to live that feeling again. To satisfy the need, they repeat the act of consuming the substance reinforcing the dopamine surge. Next dopamine surge requires more amount of substance than the previous therefore the quanity of subtance increases and addiction develops.