Background: Symptoms of depersonalisation (DP) and derealisation (DR) are increasingly recognised in both clinical and non-clinical settings, but their importance and underlying pathophysiology is only now being addressed.
Methods: This paper is a systematic review of the current state of knowledge about the prevalence of depersonalisation and derealisation using computerised databases and citation searches. All potential studies were examined and numerical data included. Three categories of study are reviewed: questionnaire and interview surveys of selected student and non-clinical samples; population-based community surveys using standardised diagnostic interviews; and clinical surveys of depersonalisation/derealisation symptoms occurring within inpatients with psychiatric disorders. In addition, we present newly analysed data of the prevalence of depersonalisation/derealisation from five large population-based studies.
Results: Epidemiological surveys demonstrate that transient symptoms of depersonalisation/derealisation in the general population are common, with a lifetime prevalence rate of between 26 and 74% and between 31 and 66% at the time of a traumatic event. Community surveys employing standardised diagnostic interviews reveal rates of between 1.2 and 1.7 % for one month prevalence in a UK sample and a 2.4% current prevalence rate in a Canadian sample. Current prevalence rates in samples of consecutive inpatient admissions are reported between 1 and 16%, although screening measures employed may have resulted in these being an underestimate. Prevalence rates in clinical samples of specific psychiatric disorders vary between 30% of war veterans with PTSD and 60% of those with unipolar depression. There is a high prevalence within panic disorder with rates varying from 7.8 to 82.6%.
Discussion: DP and DR symptoms are common in normal and psychiatric populations, but prevalence estimates are hampered by inconsistent definitions and the use of variable time-frames. Population-based surveys using diagnostic interviews yield prevalence rates of clinically significant DP/DR in the region of 1-2%. Surveys of clinical populations in which common screening and assessment instruments were used also yield consistently high prevalence rates. The use of reliable diagnostic assessments and rating scales is needed. The relationship between DP/DR and certain other psychiatric disorders (e. g. panic) suggests possible common pathophysiological or aetiological factors.