Symptoms of depersonalisation/derealisation disorder may start gradually or suddenly. Episodes may last for only hours or days or for weeks, months, or years. Episodes may involve depersonalization, derealization, or both.

The intensity of symptoms often waxes and wanes. But when the disorder is severe, symptoms may be present and remain at the same intensity for years or even decades.

Depersonalisation symptoms involve

• Feeling detached from one's body, mind, feelings, and/or sensations

People may also say they feel unreal or like an automaton, with no control over what they do or say. They may feel emotionally or physically numb. Such people may describe themselves as an outside observer of their own life or the “walking dead.”

Derealisation symptoms involve

• Feeling detached from the surroundings (people, objects, or everything), which seem unreal

People may feel as if they are in a dream or a fog, or as if a glass wall or veil separates them from their surroundings. The world seems lifeless, colourless, or artificial. The world may appear distorted to them. For example, objects may appear blurry or unusually clear, or they may seem flat or smaller or larger than they are. Sounds may seem louder or softer than they are. Time may seem to be going too slow or too fast.

The symptoms almost always cause great discomfort. Some people find them intolerable. Anxiety and depression are common. Many people are afraid that the symptoms result from irreversible brain damage. Many worry about whether they really exist or repeatedly check to determine whether their perceptions are real.

Stress, worsening depression or anxiety, new or overstimulating surroundings, and lack of sleep can make symptoms worse.