Interest in the therapeutic potential of psychedelic substances has recently resumed. During an early phase of human psychedelic research, their therapeutic application in different pathologies had been suggested, and the first evidence for efficacy was provided. The range of recent clinical applications of psychedelics spans from cluster headaches and obsessive-compulsive disorder to addiction and the treatment of fear and anxiety in patients suffering from terminal illness, indicating potentially different therapeutic mechanisms. A variety of approaches in psychotherapy emphasize subjective experiences, such as so-called peak experiences or afterglow phenomena, as differentially mediating therapeutic action. This review aims to re-evaluate earlier and recent concepts of how psychedelic substances may exert beneficial effects. After a short outline of neurophenomenological aspects, we discuss different approaches to how psychedelics are used in psychotherapy. Finally, we summarize evidence for the relationship between subjective experiences and therapeutic success. While the distinction between pharmacological and psychological action obviously cannot be clear-cut, they do appear to contribute differently from each other when their effects are compared with regard to pathologies.

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Several polymorphisms of the transcription factor 4 (TCF4) have been shown to increase the risk for schizophrenia, particularly TCF4 rs9960767. This polymorphism is associated with impaired sensorimotor gating measured by prepulse inhibition-an established endophenotype of schizophrenia. We therefore investigated whether TCF4 polymorphisms also affect another proposed endophenotype of schizophrenia, namely sensory gating assessed by P50 suppression of the auditory evoked potential. Although sensorimotor gating and sensory gating are not identical, recent data suggest that they share genetic fundamentals. In a multicenter study at six academic institutions throughout Germany, we applied an auditory P50 suppression paradigm to 1,821 subjects (1,023 never-smokers, 798 smokers) randomly selected from the general population. Samples were genotyped for 21 TCF4 polymorphisms. Given that smoking is highly prevalent in schizophrenia and affects sensory gating, we also assessed smoking behavior, cotinine plasma concentrations, exhaled carbon monoxide, and the Fagerström Test (FTND). P50 suppression was significantly decreased in carriers of schizophrenia risk alleles of the TCF4 polymorphisms rs9960767, rs10401120rs, rs17597926, and 17512836 (P < 0.0002-0.00005). These gene effects were modulated by smoking behavior as indicated by significant interactions of TCF4 genotype and smoking status; heavy smokers (FTND score ≥4) showed stronger gene effects on P50 suppression than light smokers and neversmokers. Our finding suggests that sensory gating is modulated by an interaction of TCF4 genotype with smoking, and both factors may play a role in early information processing deficits also in schizophrenia. Consequently, considering smoking behavior may facilitate the search for genetic risk factors for schizophrenia.R ecent large genomewide association studies (GWAS) identified and consistently confirmed that common variants of the transcription factor 4 (TCF4) gene contribute to the risk of schizophrenia (1-3). In these analyses, two single nucleotide polymorphisms (SNPs) located in the intron of the TCF4 gene on chromosome 18q21.1 (rs9960767, rs17512836) and an intragenic SNP near the TCF4 gene (rs4309482) have shown the strongest association with the disease (1-3). TCF4 is a class I basic helixloop-helix (bHLH) protein involved in the control of neuronal and glial progenitor cells, which are important for the development of the mammalian central nervous system (CNS) (4, 5).The exact role of TCF4 in the brain and the functional activity of these nonsynonymous TCF4 variants on the level of gene expression are not yet fully understood (4, 6). A recent postmortem study suggested that the rs9960767 SNP is neither functional nor affects mRNA expression in the adult human brain, indicating that TCF4 mutations may exert their effects on expression through posttranscriptional effects or exclusively in a developmental context (e.g., by gene-environment interactions) (7).In a translational animal study, it was initially shown that tra...