do science on ASCs from within such states. Classification A classification of Altered States of Consciousness is helpful if one wants to compare or differentiate between induced ASCs and other variations of consciousness. Various researchers have attempted the classification into a broader framework. The attempts of classification discussed in the following focus on slightly different aspects of ASCs. Several authors suggested classification schemata with regard to the genesis of altered states and with regard to the type of experiences: A classification with five categories was suggested by Vaitl to distinguish ASCs according to how they were induced: Pathological (Epilepsy, brain damage) Pharmacological (psychoactive substances) Physical and physiological (fasting and sex) Psychological (music, meditation, hypnosis) Spontaneous (day-dreaming and near death experience) Vaitl further suggests four basic aspects of experiences: (1) activation (2) awareness span (3) self-awareness (4) sensory dynamics. Alternatively Roland Fischer suggests a classification along ergotropic (i.e., ecstasy) or trophotropic (i.e., meditation) properties. The work of Adolph Dittrich aimed to empirically determine common underlying dimensions of consciousness alterations induced by different methods, such as drugs or non-pharmacological methods. He suggested three basic dimensions, which were termed: (1) oceanic boundlessness (2) dread of ego dissolution (3) visionary restructuralization. Further, Ken Wilber proposes a multidimensional system and adds that the individual experience of an ASC is shaped by a person's unique psychological development. Michael Winkelman identifies four different "modes of consciousness": (1) the waking mode (2) the deep sleep mode (3) the REM sleep / dreaming mode (4) the integrative mode. Within this framework, many ASCs (psychedelics, hypnosis, meditation, etc.) are defined as belonging to the integrative mode. Induction methods Pharmacological An altered state of consciousness may be defined as a short-term change in the general configuration of one's individual experience, such that the rational functioning is clearly altered from one's usual state of consciousness. There are many ways that one's consciousness can be altered, such as by using psychoactive drugs, which are defined as chemical substances that pass through the blood brain barrier and disturb brain function, causing changes in awareness, attitude, consciousness, and behavior. Cannabis is a psychoactive drug that is known to alter the state of consciousness. Cannabis alters mental activity, memory, and pain perception. One who is under the influence of cannabis may (or may not) experience degrees of paranoia, increased sensitivity, and delayed reactions not normal for their usual conscious state. A 2009 review of anxiety and