The case for viewing depression as a consciousness disorder

The symptoms of depression are well characterized, but the subjective experiences of a depressed person are much harder to pin down. 

According to the Diagnostic Statistical Manual, the core symptoms of Major Depressive Disorder include depressed mood and a markedly diminished interest or pleasure in all, or almost all, activities. These can be accompanied by changes in appetite and weight, sleep disturbances, fatigue, feelings of guilt or worthlessness, a reduced ability to think or concentrate, and sometimes suicidal ideation.      

Beyond these clinical symptoms, depressed patients seem to experience the world differently from others. This is reflected in terms used to describe a depressed state, such as feeling “blue” — and there is indeed some evidence that depression alters sensory perception. 

Depressed patients also report that their conscious experience has changed or been disturbed such that they feel detached from the world and other people. This aspect of depression is impossible to quantify. Psychiatrists have struggled to understand it.

A global state

A new hypothesis seeks to explain the experiential aspect of depression. 

In a paper published in The British Journal for the Philosophy of Science, Cecily Whiteley of the London School of Economics describes depression as an altered state of consciousness. Whiteley suggests that thinking about depression in this way has important implications for a neuroscientific understanding of the condition and the emerging field of psychedelic psychiatry.

According to Whiteley, depression involves entrance into a distinct “global state” of consciousness, which involves a major change in the range and quality of a subject’s conscious experiences. It can be regarded as a state of mind similar to dreaming and the psychedelic state, as well as disorders of consciousness such as minimal consciousness and vegetative states.  

Thus, depression involves shifting from one global state of consciousness to another. When an individual becomes depressed, they shift from the normal state of wakefulness into the depressive state.

This shift entails a change in conscious experience and mental life, according to Whiteley. It alters the individual’s experience of their body, causing them to feel numb and lethargic and diminishing their sense of agency or control. It distorts their cognitive functions and their self-narrative, reducing their ability to concentrate or think hopefully. It also changes their perception of time, making the future feel closed off. Finally, it alters how they relate to others, making them feel estranged and disconnected.   

According to Whiteley, thinking of depression as a global state of consciousness could help understand why no satisfying explanation of the disorder’s mechanics exists. Since we still know so little about how the brain gives rise to any global state of consciousness, the neural mechanisms underlying depression lie well beyond our reach. 

Can psychedelics beat depression?

Whiteley further argues that her proposed depressive state of consciousness helps to explain the apparent successes of psychedelic psychiatry. 

Although still in its infancy, research into the therapeutic benefits of psychedelic-assisted psychotherapy has already yielded some positive results. In particular, psilocybin and ketamine show potential benefits for patients with depression and other mental disorders.

Psychedelics are well known to produce profound changes in consciousness, and they may do so by triggering a transition from one global state of consciousness to another. In the case of depression, they might be able to shift patients from the depressed to the psychedelic state, eventually reinstating the normal state of wakefulness.  

Although largely hypothetical right now, Whiteley’s thesis could have clinical applications. For example, perhaps neuroimaging techniques could distinguish between different global states of consciousness by measuring the complexity of long-range connections in the brain. If, as Whiteley claims, depression is one such global state, this method could provide an objective diagnostic test.