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K. Kovar

[Hallucinogen-induced psychological disorders]

June 1, 2008 / LSD, Mushrooms / Psilocybin, Neuroscience, Papers, Psychology, Psychotic Disorders, Publications / By / , , ,

Abstract

OBJECTIVE:

The purpose of this article is to provide an overview of the current research on hallucinogen induced psychiatric disorders. In addition to LSD and psilocybin hallucinogens of biologic origin are increasingly used by adolescents and young adults.

METHODS:

Relevant literature and related articles were identified by means of a computerized MEDLINE search including the years 1997 – 2007. As keywords “hallucinogen induced psychosis”, “hallucinogen induced flashback”, “hallucinogen persisting perception disorder (HPPD)” were used. Finally, 64 journal articles and books out of 103 were included in the review.

RESULTS:

Acute psychotic syndromes in adolescents are rarely due to intoxications with hallucinogenic drugs. However, clinical relevance of flashback phenomena as post-hallucinogenic psychiatric disorder has to be disputed. Because of the high popularity of biogenic hallucinogens and LSD knowledge of intoxications and resulting psychiatric disorders as well as medical complications and therapeutical approaches are clinically important. Especially intoxications with drugs of herbal origin like tropanalcaloids play an important role in emergency situations.

Hermle, L., Kovar, K. A., Hewer, W., & Ruchsow, M. (2008). [Hallucinogen-induced psychological disorders]. Fortschritte der Neurologie-Psychiatrie, 76(6), 334-342. http://dx.doi.org/10.1055/s-2008-1038191
Link to full text [Article in German]

Psychological effects of (S)-ketamine and N,N-dimethyltryptamine (DMT): a double-blind, cross-over study in healthy volunteers

October 1, 2005 / DMT, Ketamine, Papers, Psychology, Psychotic Disorders, Publications / By / , , , , , ,

Abstract

INTRODUCTION:
Pharmacological challenges with hallucinogens are used as models for psychosis in experimental research. The state induced by glutamate antagonists such as phencyclidine (PCP) is often considered as a more appropriate model of psychosis than the state induced by serotonergic hallucinogens such as lysergic acid diethylamide (LSD), psilocybin and N,N-dimethyltryptamine (DMT). However, so far, the psychological profiles of the two types of hallucinogenic drugs have never been studied directly in an experimental within-subject design.

METHODS:
Fifteen healthy volunteers were included in a double-blind, cross-over study with two doses of the serotonin 5-HT2A agonist DMT and the glutamate N-methyl-D-aspartate (NMDA) antagonist (S)-ketamine.

RESULTS:
Data are reported for nine subjects who completed both experimental days with both doses of the two drugs. The intensity of global psychological effects was similar for DMT and (S)-ketamine. However, phenomena resembling positive symptoms of schizophrenia, particularly positive formal thought disorder and inappropriate affect, were stronger after DMT. Phenomena resembling negative symptoms of schizophrenia, attention deficits, body perception disturbances and catatonia-like motor phenomena were stronger after (S)-ketamine.

DISCUSSION:
The present study suggests that the NMDA antagonist model of psychosis is not overall superior to the serotonin 5-HT2A agonist model. Rather, the two classes of drugs tend to model different aspects or types of schizophrenia. The NMDA antagonist state may be an appropriate model for psychoses with prominent negative and possibly also catatonic features, while the 5-HT2A agonist state may be a better model for psychoses of the paranoid type.

Gouzoulis-Mayfrank, E., Heekeren, K., Neukirch, A., Stoll, M., Stock, C., Obradovic, M., & Kovar, K .A. (2005). Psychological effects of (S)-ketamine and N,N-dimethyltryptamine (DMT): a double-blind, cross-over study in healthy volunteers. Pharmacopsychiatry, 38(6), 301-311. http://dx.doi.org/10.1055/s-2005-916185
Link to full text

Increased Activation of Indirect Semantic Associations under Psilocybin

June 15, 1996 / Mushrooms / Psilocybin, Papers, Psychology, Publications / By / , , , , , ,

Abstract

The spread of activation in semantic networks can be measured using semantic and indirect semantic priming effects in lexical decision tasks (Spitzer et al 1993a and b). For example, in thought-disordered schizophrenic patients, activation spreads faster and farther than in non-thought-disordered patients and normal subjects, which results in an increased direct and indirect semantic priming effect (see below). This has been interpreted as the result of a decreased signal-to-noise ratio in cortical neural networks that process semantic information. Such a decreased signal-to-noise ratio has been related to a decreased dopaminergic modulation (Servan-Schreiber et al. 1990; Cohen and Servan- Schreiber 1992, 1993), which we recently were able to confirm directly in a study on the effects of L-dopa on semantic and indirect semantic priming (Kischka et al 1995).

As dopamine was found to have a focusing effect on the activity in semantic networks, i.e., it increases the signal-to-noise ratio and reduces the spread of activation (measured as reduced indirect semantic priming), we set out to investigate the effect of the hallucinogenic agent psilocybin on this task. Since psilocybin is known to act on the serotonin (5-HT) system and has effects of “broadening” conscious experiences, we hypothesized that it might exert a defocusing effect on semantic networks (i.e., decrease the signal-to-noise ratio), which should lead to an increased indirect semantic priming effect.

To test this hypothesis directly, we conducted a double-blind, placebo-controlled study on the effects of psilocybin on semantic and indirect semantic priming as part of a larger project that was designed to assess the behavioral effects and pharmacokinetic properties of this hallucinogenic agent (the results will be reported elsewhere; cf. Holzmann 1995).

Spitzer, M., Thimm, M., Hermle, L., Holzmann, P., Kovar, K., Heirnann, H., … Schneider, F. (1996). Increased Activation of Indirect Semantic Associations under Psilocybin. Biological Psychiatry, 39(12),  1055–1057. http://dx.doi.org/10.1016/0006-3223(95)00418-1
Link to full text

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