“Normally, dopamine recycles back into the cell that released it, shutting off the signal between nerve cells. However, cocaine prevents dopamine from being recycled, causing large amounts to build up. This flood of dopamine in the brain’s reward circuit strongly reinforces drug-taking behaviors, because the reward circuit eventually adapts to the excess of dopamine caused by cocaine, and becomes less sensitive to it. As a result, people take stronger and more frequent doses in an attempt to feel the same high.”
…While scientists are still researching exactly why cocaine and other stimulants cause sleep loss, recent studies have shown that the surge in dopamine affects the body’s circadian rhythms. Since circadian rhythms regulate sleep patterns, this leads to difficulty both staying and falling asleep.