Body Perception Disturbance Research Articles

Psychological Effects of (S)-Ketamine and N,N-Dimethyltryptamine (DMT): A Double-Blind, Cross-Over Study in Healthy Volunteers

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. 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. 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. 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.

A reappraisal of body perception disturbance in anorexia nervosa.

Previous research has suggested that patients suffering from anorexia nervosa tend to overestimate their body size, whereas normal females tend to be very accurate in this respect. This paper presents the results of further investigations of body perception amongst anorexic and normal females. The results, in contrast to earlier findings, indicate no such difference between groups. Detailed analysis of the data, however, points to the likelihood of certain differences between the present group of anorexic patients and previous groups. Moreover, it seems that body perception disturbance is not a consistent feature of anorexia nervosa and is only present amongst some patients at certain stages during their illness. On subdividing the anorexic group it was demonstrated that patients who vomit tend to overestimate their size more than do non-vomiters. It also seems likely that normal females are far from homogeneous in terms of body perception. In line with previous findings, a direct relationship was found between marked overestimation of body size and an early relapse. Evidence is also discussed which suggests that body perception disturbance is not specific to anorexia nervosa and may reflect an abnormal sensitivity about body size associated with such factors as the anticipation of an undesired change in weight, extreme concern about slimness and anxiety about putting on weight.