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Depersonalisation disorder

Many people experience brief episodes of detachment, but for others 鈥渄epersonalisation鈥� is an everyday part of life. The Diagnostic and Statistical Manual of Mental Disorders IV defines it as 鈥渁 feeling of detachment or estrangement from one鈥檚 self鈥� The individual may feel like an automaton or as if he or she is living in a dream or a movie. There may be a sensation of being an outside observer of one鈥檚 mental processes, one鈥檚 body, or parts of one鈥檚 body.鈥� There is some evidence that this state is caused by a malfunction of the body鈥檚 emotion systems ().

The petrified self

A crucial building block of selfhood is the autobiographical self, which allows us to recall the past, project into the future and view ourselves as unbroken entities across time. Key to this is the formation of memories of events in our lives.

Read more: Your true self

Who are you? An entity continuous in time, an individual with a personality, a unique bundle of memories? Only now are we truly getting to grips with what our sense of self is and isn鈥檛, and how it can change 鈥� insights that could help us live better with ourselves and with others

Autobiographical memory formation is one of the first cognitive victims of Alzheimer鈥檚 disease. This lack of new memories, along with the preservation of older ones, may be what leads to the outdated sense of self 鈥� or 鈥減etrified self鈥� 鈥� often seen in the early stages of the disease. It could also be what causes a lack of self-awareness of having the illness at all ().

Body integrity identity disorder

Imagine a relentless feeling that one of your limbs is not your own. That is the unenviable fate of people with body integrity identity disorder. They often feel it so intensely that they end up amputating the 鈥渇oreign鈥� part.

The disorder can be viewed as a perturbation of the bodily self caused by a mismatch between the internal map of one鈥檚 own body and physical reality. Neuroimaging studies by Peter Brugger of University Hospital Zurich in Switzerland have shown that the network of brain regions responsible for creating a sense of bodily self is different in people with the condition (Brain, vol 136, p 318).

Psychedelics

One of the most reliable 鈥� and reversible 鈥� ways to alter your sense of self is to ingest psychedelic drugs such as LSD or psilocybin, the active ingredient in magic mushrooms.

Alongside sensory distortions such as visual hallucinations, a common psychedelic experience is a feeling that the boundary between one鈥檚 self and the rest of the world is dissolving. A team led by David Nutt of Imperial College London recently discovered why: psilocybin causes a reduction in activity in the anterior cingulate cortex, a part of the brain thought to be involved in integrating perception and the sense of self. It was assumed that psychedelics worked by increasing brain activity; it seems the opposite is true (PNAS, vol 109, p 2138).

Cotard鈥檚 delusion

Of all the disturbances of the self, the eeriest and least understood is Cotard鈥檚 syndrome. Symptoms of this very rare syndrome range from claims that blood or internal organs have gone missing to disavowal of the entire body and a belief that one is dead or has ceased to exist. People with the delusion 鈥� who are often severely depressed or psychotic 鈥� have been known to plan their own funerals.

This article appeared in print under the headline 鈥淲hen the self breaks鈥�