Psychological consciousness studies involve research on levels and states of consciousness. Psychologically researched levels of consciousness are the conscious, preconscious, unconscious/subconscious, and nonconscious levels of mental processing. Psychological research on states of consciousness – which is the main focus of this course – takes waking consciousness as the most common state (ordinary state of consciousness, OSC), using it as a baseline against which altered states of consciousness (ASCs) are compared. Some of the most prominently researched ASCs in psychology will be introduced in this course and include sleeping/dreaming, hypnosis, meditation, sensory deprivation (floating tank), absorption, as well as ASCs induced by psychoactive drugs (classic psychedelics, dissociative anesthetics, empathogens). Furthermore, it will also be shown how a growing number of clinical studies investigate the therapeutic potential of being temporarily in an ASC.