The experimental induction of altered states of consciousness (ASC) constitutes a research opportunity to relate changes in phenomenological states to underlying biophysical mechanisms. A variety of pharmacological and non-pharmacological methods were reported to induce consciousness alterations in humans, ranging from the consumption of psychoactive drugs to special breathing techniques or sensory deprivation. Within psychological experiments, the subjective experiences of ASCs are typically quantified with retrospective questionnaires. Here, we introduce a database, termed the Altered States Database (ASDB), comprised of questionnaire data extracted from original research articles. The database contains data from articles published in MEDLINE-listed journals from experimentally induced altered states that were assessed with a specified set of standardized questionnaires. The dataset at hand will allow direct comparisons of the psychological effects of different induction methods as well as meta-analyses to establish induction method specific dose-response relationships.