Prevalence represents the overall proportion of individuals in a population who have the disorder of interest. It is different from incidence, which represents only the new cases that have developed over a particular time period. Point prevalence is the proportion of individuals in a population who have the disorder at a given point in time (e.g., at one-month post-trauma), while period prevalence is the proportion of individuals in a population who have the disorder over specific time periods (e.g., one to two months post-trauma). Lifetime prevalence is the proportion of individuals in a population who have ever had the disorder and lifetime morbid risk also includes those who had the disorder but who were deceased at the time of the survey.

What is the evidence for spatial variation in the prevalence of PTSD?

Moderate quality evidence finds the overall lifetime prevalence of PTSD in the population is around 3.9%. Lifetime rates were higher in high-income countries (5%) than in upper-middle or low-middle income countries (both around 2%). Lifetime rates were higher in the WHO Western Pacific region (5.7%), the Western European region (4.0%) and the Americas (3.8%), than in the Eastern European region (2.4%), Africa (2.3%) and the Eastern Mediterranean region (2.1%). However, the pooled current and lifetime prevalence of PTSD in the Eastern Mediterranean region is around 7%. The 10-year prevalence of PTSD in South Asia (India, Pakistan, Nepal, Sri Lanka, and Bangladesh) is around 17%.

October 2021

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Prevalence rates of bipolar disorder may differ across regions. Prevalence quantifies the proportion of individuals in a population who have a disease during a specific time period, while incidence refers to the number of new cases of disease that develop in a population during a specific time period. In disorders of short duration, incidence and prevalence rates may be similar, however with disorders of long duration such as with bipolar disorder there can be variation between the two. Point prevalence is the proportion of individuals who manifest a disorder at a given point in time, period measures the proportion of individuals who manifest a disorder during a specified period (e.g. one year), lifetime is the proportion of individuals in the population who have ever manifested a disorder who are alive on a given day and lifetime morbid risk also includes those deceased at the time of the assessment.

Is there variation in prevalence rates of bipolar disorder across countries?

Moderate quality evidence finds the lifetime prevalence rates of bipolar disorders are significantly higher in North America (2.9%), South America (3%), Australia (2.1%) and Europe (1.7%), than in the Middle East (1.1%), Africa (0.7%), and Asia (0.5%).

The 10-year prevalence of bipolar disorder in South Asia (India, Pakistan, Nepal, Sri Lanka, and Bangladesh) is around 0.6%. The pooled prevalence of bipolar disorder in the WHO Eastern Mediterranean region (Iran, Pakistan, Egypt, Lebanon, Sudan, Saudi Arabia, Morocco, Iraq, Afghanistan, Jordan, Qatar, Bahrain, Palestine, United Arab Emirates, and Tunisia) is around 0.7%. Current prevalence is around 1.9%, lifetime prevalence is around 0.2%, and period (6-12 month) prevalence is around 0.6% in the WHO Eastern Mediterranean region.

October 2021

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Prevalence measures the proportion of individuals who have a disorder at a particular point in time (point prevalence) or during a specified period (annual prevalence, lifetime prevalence) and this may vary across regions. It is distinct from incidence, which refers to how many new cases there are per population in a specified time period. Lifetime prevalence is the number of individuals in a population that at some point in their life have experienced schizophrenia compared to the total number of individuals.

What is the evidence for spatial variation in prevalence rates of schizophrenia?

High quality evidence indicates there is worldwide spatial variation in the prevalence of schizophrenia and schizophrenia-related disorders. There is increased prevalence of schizophrenia with higher latitudes and colder climates. At the same latitude, prevalence is higher for people with dark skin colour (African American, sub-Saharan Africa and southern Indian regions). Moderate quality evidence suggests there is less prevalence in least developed countries compared to developed countries. High quality evidence suggests no differences in the prevalence of schizophrenia in urban versus rural or mixed urban/rural areas. The age-standardised 2016 prevalence rate was 0.28%, with variance from 0.19% in Africa, to 0.42% in East Asia.

April 2022

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