A study evaluated the frequency of migraine among people with Hallucinogen Persisting Perception Disorder (HPPD) presenting as visual snow syndrome (VSS). There were no cases of migraine among the people with HPPD, but more than half of controls had migraine. Both groups had a median Visual Snow Handicap Inventory score of 38 out of 100. Most cases of visual snow in HPPD cases started after taking ecstasy.

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