Occasional moderate drinking may help with sleep, but long-term or excessive alcohol consumption can instead cause insomnia, because the sedative effect of alcohol is short-lived, typically lasting only 3 to 4 hours. Once this hypnotic effect wears off, symptoms of sympathetic nervous system activation, such as a rebound increase in heart rate and rapid breathing, can occur, making it easier to wake up and even leading to insomnia. Moreover, long-term heavy drinking increases the body's tolerance to ethanol, requiring progressively larger amounts of alcohol to achieve only a brief sedative effect, which is then followed by more severe insomnia.