Cocaine addiction is the excessive intake of cocaine, and can result in physiological damage, lethargy, depression, or a potentially fatal overdose. Though the immediate craving to do more cocaine is strong and very common, this feeling usually subsides in most users within an hour of the last dosage. This craving can, as it has in many users, develop rather quickly into an intense psychological addiction. Many habitual abusers have been diagnosed with a manic condition similar to amphetamine psychosis and schizophrenia, whose symptoms include aggression, severe paranoia, and tactile hallucinations (including the feeling of insects under the skin, or "coke bugs").
Cocaine has positive reinforcement effects, which refers to the effect that certain stimuli have on behavior. Good feelings become associated with the drug, causing a frequent user to take the drug as a response to bad news or mild depression. This activation strengthens the response that was just made. If the drug was taken by a fast acting route such as injection or inhalation, the response will be the act of taking more cocaine, so the response will be reinforced. Powder cocaine, being a club drug is mostly consumed in the evening and night hours. Because cocaine is a stimulant, a user will often drink large amounts of alcohol during and after usage or smoke marijuana to dull the effects and promote slumber. These several hours of temporary relief and pleasure will further reinforce the positive response. Other downers such as heroin and various pharmaceuticals are often used for the same purpose, further increasing addiction potential and harmfulness.
It is speculated that cocaine's addictive properties stem from its DAT-blocking effects (in particular, increasing the dopaminergic transmission from ventral tegmental area neurons). However, a study has shown that mice with no dopamine transporters still exhibit the rewarding effects of cocaine administration.  Later work demonstrated that a combined DAT/SERT knockout eliminated the rewarding effects. The rewarding effects of cocaine are influenced by circadian rhythms , possibly by involving a set of genes termed "clock genes".