The Confessions maintained a place of primacy in De Quincey's literary output, and his literary reputation, from its first publication; "it went through countless editions, with only occasional intervals of a few years, and was often translated. Since there was little systematic study of narcotics until long after his death, De Quincey's account assumed an authoritative status and actually dominated the scientific and public views of the effects of opium for several generations."
Yet from the time of its publication, De Quincey's Confessions was criticized for presenting a picture of the opium experience that was too positive and too enticing to readers. As early as 1823, an anonymous response, Advice to Opium Eaters, was published "to warn others from copying De Quincey." The fear of reckless imitation was not groundless: several English writers — Francis Thompson, James Thomson, William Blair, and perhaps Branwell Brontë — were led to opium use and addiction by De Quincey's literary example. Charles Baudelaire's 1860 translation and adaptation, Les paradis artificiels, spread the work's influence further. One of the characters of the Sherlock Holmes story, The Man with the Twisted Lip (1891), is an opium addict who began experimenting with the drug as a student after reading the Confessions. De Quincey attempted to address this type of criticism. When the 1821 original was printed in book form the following year, he added an Appendix on the withdrawal process; and he inserted significant material on the medical aspects of opium into his 1856 revision.
More generally, De Quincey's Confessions influenced psychology and abnormal psychology, and attitudes towards dreams and imaginative literature.
Confessions of an English Opium-Eater also served as inspiration to one of Hector Berlioz's most famous pieces, Symphonie Fantastique. The play The Opium Eater by Andrew Dallmeyer was also based on Confessions of an English Opium-Eater, and has been published by Capercaillie Books.