What causes premature ejaculation?

What causes premature ejaculation?
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Although the exact cause of premature ejaculation is not known, new studies suggest that serotonin, a natural substance produced by nerves, is important. A breakdown of the actions of serotonin in the brain may be a cause. Studies have found that high amounts of serotonin in the brain slow the time to ejaculation while low amounts of serotonin can produce a condition like premature ejaculation.