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Abstract
'Flashbacks' following use of hallucinogenic drugs have been reported for decades;
they are recognized in DSM-IV as 'Hallucinogen Persisting Perception Disorder (Flashbacks)',
or HPPD. We located and analyzed 20 quantitative studies between 1955 and 2001 examining
this phenomenon. However, many of these studies were performed before operational
criteria for HPPD were published in DSM-III-R, so they are difficult to interpret
in the light of current diagnostic criteria. Overall, current knowledge of HPPD remains
very limited. In particular (1) the term 'flashbacks' is defined in so many ways that
it is essentially valueless; (2) most studies provide too little information to judge
how many cases could meet DSM-IV criteria for HPPD; and consequently (3) information
about risk factors for HPPD, possible etiologic mechanisms, and potential treatment
modalities must be interpreted with great caution. At present, HPPD appears to be
a genuine but uncommon disorder, sometimes persisting for months or years after hallucinogen
use and causing substantial morbidity. It is reported most commonly after illicit
LSD use, but less commonly with LSD administered in research or treatment settings,
or with use of other types of hallucinogens. There are case reports, but no randomized
controlled trials, of successful treatment with neuroleptics, anticonvulsants, benzodiazepines,
and clonidine. Although it may be difficult to collect large samples of HPPD cases,
further studies are critically needed to augment the meager data presently available
regarding the prevalence, etiology, and treatment of HPPD.
Copyright 2002 Elsevier Science Ireland Ltd.