A mental health condition involving persistent feelings of detachment from oneself or surroundings, as if observing from outside.
Medical records documenting your formal diagnosis of Depersonalization/Derealization disorder are the starting point. Beyond that, evidence needs to reflect how your symptoms affect your ability to work and function day to day, because the rating levels are defined by that impact.
For the higher ratings, records showing symptoms such as panic attacks and how often they occur, sleep disturbance, memory difficulties, problems with speech or thinking, impaired judgment, suicidal ideation, disorientation, or difficulty maintaining personal hygiene can all be relevant. Mental health treatment notes, psychiatric evaluations, and neuropsychological testing can document the nature and severity of these symptoms.
Statements from you describing how symptoms interfere with your job, schooling, or family relationships are relevant at every level. Statements from people who know you, such as a spouse, coworker, or supervisor, can corroborate what your daily functioning actually looks like. If continuous medication is part of your treatment, records showing that are relevant to the 10% level.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.
