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Studies have found that creative skills are more common in people who have mental illness in their families, and are associated with a higher risk of schizophrenia and bipolar disorder. Also, certain psychological traits, such as the ability to make unusual or bizarre associations are shared by schizophrenics and healthy, highly creative people.
Some research has also found an association between creative abilities and the brain's dopamine system — the network of neurons set up to respond to dopamine. (Dopamine is a neurotransmitter that, amongst other things, is involved in the reward response to everything from chocolate to cocaine.) However, the mechanism behind the dopamine-creativity link was largely a mystery.