Cocaine and stimulants also heighten the body's sensitivity to stress, but in a different way. For example, when a cocaine user takes cocaine, the stress systems are activated much like when an opiate user goes into withdrawal, but on cocaine the person perceives this as part of the cocaine rush because the drug is also stimulating parts of the brain involved in reward. When the acute effects ware off, the stress systems are activated - again much like when an opiate addict goes into withdrawal. This time the cocaine user perceives the activation as unpleasant because the pleasure circuits are no longer being stimulated. Because stimulants such as cocaine activate the stress system both when initially consumed and again during withdrawal, the stress system becomes hypersensitive quite rapidly - often before the user fully appreciates the change that has taken place.
Studies link stress and drug addiction .