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A Chronic Impairment of Colour Vision in Users of LSD
HENRY DAVID ABRAHAM
Summary: Forty-six users of the hallucinogen lysergic acid diethylamide were
compared with 31 controlson a testof colour discriminationan average of two
years after their last exposure to the drug. Controls performed better than users,
and LSD users without flashbacks performed better than users with flashbacks.
An analysis of variance between the three groups was significant at P <0.001.
This study suggests that some users of LSD may have a sustained or irreversible
impairment in colour discrimination.