When most people who are healthy are conscious the brain produces a variety of measurable and fairly predictable brain wave types. These change when people do things like sleeping, if they take certain medications or illegal drugs, when they meditate or pursue a variety of other activities that change consciousness. The above activities and many others create what is known as an altered state of consciousness.
Definitions for an altered state of consciousness can vary depending on the source. Essentially, there is dissociation between the mind and body connection. Or alternately, the self as perceived psychologically, is not dually perceived as necessarily connected to the body. Perception of the self may be very different and some of the normal restrictions of the self, what Sigmund Freud might call ego and superego may be lifted.
Most people enter an altered states in dreaming. In dreams, people can do many things they either could not or would not do in ordinary life. They might commit a murder or have an affair, since presence of the normal sense of “morality” is lifted during a dreaming state. Dreams also free people to do things that aren’t physically possible, such as breathing underwater or flying. Some dreams are highly imaginative and entertaining, while others are very frightening.
It’s difficult to avoid dreaming, even when people have little recollection of their dreams. There are many other altered states into which people may enter without choice. A very high fever, a seizure, and some forms of mental illnesses, particularly dissociative disorders may change perception of mind and body, and of their connection. People requiring pain medication that is opiate-based might experience an altered state of consciousness too.
There are many who theorize these altered states fuel creativity and can lead to better perception in the conscious state. For a while, in the 1960s, there were many who advocated inducing altered states of consciousness through methods like sensory deprivation or by taking known hallucinogens such as magic mushrooms or acid. Such studies were mostly discredited.
Yet, there are many psychologists and others who advocate working in different states of consciousness at some times to promote better understanding of the self in the conscious state. In some cases, people under hypnosis reach an altered state. They may have access to the unconscious brain or a better way of understanding some of the ways the conscious brain acts.
Other people may reach an altered state of consciousness through different types of activities. Certain forms of prayer, chanting, meditation or yoga may cause mind/body dissociation. These dissociations can promote extremely positive feelings, especially when a person returns to regular consciousness, which then reward the person for entering the altered state and may encourage interest in re-entering it.
The experiments that led to drug use to enter altered states, and fear that an altered state somehow represents witchcraft or association with paganism leads some people to criticize all such states, and intentional entry to them. However, these critics cannot avoid dreaming, getting a high fever or possible diagnosis with mental illness. There’s little evidence to suggest that an altered state is evil or based in paganism; instead these differences in conscious perception occur to all people, and most cultures have created unique interpretations of altered states.
It’s clearly unadvisable to use illegal drugs to enter an altered stated of consciousness, though in some native cultures, it may be commonplace to use certain substances to create altered states. People must also understand that it’s widely unnecessary to try to induce an altered state of consciousness by illegal means. There are plenty of perfectly legal ways to do this while awake, and each person will certainly do so while asleep.