Prevalence rates ERQ

Introduction: What are prevalence rates?

Prevalence rates refer to how common a specific disorder is within a defined population at a given time period. They describe the proportion of individuals in a population who have a particular disorder.

Introduction: Prevalence rates and MDD

For Major Depressive Disorder (MDD), prevalence rates measure how many people in a population are diagnosed with MDD during a specified time frame, such as one year or across a lifetime.

Introduction: How prevalence rates are calculated

Prevalence is calculated by dividing the total number of diagnosed cases of a disorder by the total population size. This value can be expressed as a proportion, percentage, or cases per 100,000 people.

Introduction: Example of prevalence calculation

If 4,500 people in a population of 50,000 are diagnosed with MDD, the prevalence rate is 0.09 (4,500 ÷ 50,000), equivalent to 9,000 cases per 100,000 people.

Introduction: Why prevalence rates are useful

Prevalence rates allow researchers and policymakers to estimate how likely an individual in a population is to be diagnosed with a disorder. They are used as predictive tools to allocate healthcare resources and plan interventions.

Introduction: Focus of this ERQ

This ERQ discusses prevalence rates of MDD using global statistics and two key studies: Abdoli et al. (2022) on elderly populations and the Global Burden of Disease study (Spencer et al., 2017). Variations by age, gender, and culture are considered.

General prevalence of MDD worldwide

The World Health Organisation estimates that 3.8% of the global population suffers from MDD at any given time, equivalent to approximately 280 million people worldwide.

Prevalence of MDD by age group

Globally, prevalence is estimated at 5% for adults and 5.7% for individuals aged 60 and above, suggesting increased vulnerability in older populations.

Prevalence of MDD in the UK

The prevalence rate of MDD in the UK is approximately 0.17, meaning around 1 in 6 adults experience MDD.

Gender differences in MDD prevalence

MDD is more prevalent in women than men both globally and in the UK. Approximately 15% of women seek treatment for MDD compared to 9% of men.

Cultural variation in MDD prevalence

Prevalence rates vary by country: approximately 1% in the Czech Republic, 9% in Chile, and 16.9% in the United States, indicating sociocultural influences on diagnosis and reporting.

Abdoli et al. (2022) - Aim

To investigate the global prevalence of Major Depressive Disorder in elderly populations.

Abdoli et al. (2022) - Participants

A total sample of 18,953 participants drawn from 20 studies included in the meta-analysis. Participants represented elderly populations from multiple countries worldwide.

Abdoli et al. (2022) - Procedure

A meta-analysis was conducted using 20 studies identified through a systematic database search. Studies investigating MDD in elderly populations up to March 2021 were included.

Abdoli et al. (2022) - Results

The global prevalence rate of MDD in the elderly was 13.3%. Elderly women showed a prevalence rate of 11.9% and men 9.7%, though this gender difference was not statistically significant. The highest prevalence rates were observed in Australia (20.1%) and Europe (12.9%).

Abdoli et al. (2022) - Conclusion

MDD has a high global prevalence among elderly populations. Findings highlight the need for social support and mental health interventions for older adults. Gender differences should not lead to stereotypical assumptions in treatment.

Abdoli et al. (2022) - Strengths

The large combined sample and statistical methodology increase robustness and reliability. The study is socially relevant due to the growing global elderly population.

Abdoli et al. (2022) - Weaknesses

The study identifies prevalence rates but cannot explain why elderly individuals develop MDD, limiting explanatory power. Prevalence data rely on reported diagnoses, likely underestimating true rates due to underreporting or lack of recognition.

Global Burden of Disease (2017) - Aim

To estimate the worldwide prevalence and burden of Major Depressive Disorder and examine variations by age and gender.

Global Burden of Disease (2017) - Participants

Population-level data from multiple countries worldwide collected through epidemiological surveillance and health records.

Global Burden of Disease (2017) - Procedure

A large-scale epidemiological analysis combining national surveys, health records, and statistical modelling to estimate global prevalence rates of MDD.

Global Burden of Disease (2017) - Results

The global prevalence of MDD in 2015 was estimated at 4.4%. Depression was more prevalent among females (5.1%) than males (3.6%). Prevalence increased with age, peaking in older adulthood.

Global Burden of Disease (2017) - Additional findings

The total number of individuals living with depression increased by 18.4% between 2005 and 2015, partly due to population growth and ageing.

Global Burden of Disease (2017) - Conclusion

MDD represents a major global public health issue, with significant variation by gender and age. Increasing prevalence highlights the need for global mental health strategies.

Global Burden of Disease (2017) - Strengths

Large-scale global data increase external validity. Allows comparison across countries, genders, and age groups, making it valuable for public health planning.

Global Burden of Disease (2017) - Weaknesses

Estimates rely on reported data and modelling, which may miss undiagnosed cases. Cultural differences in diagnosis and stigma may affect accuracy of prevalence rates.

Biological explanations for gender differences

Hormonal differences and genetic vulnerability may contribute to higher prevalence of MDD in women.

Cognitive explanations for gender differences

Women may be more prone to rumination, guilt, and negative attributional styles, increasing vulnerability to depressive symptoms.

Sociocultural explanations for gender differences

Women are more likely to seek medical help, increasing diagnosis rates. Gender stereotypes among clinicians may influence diagnosis. Social isolation and caregiving roles may also increase risk.

Holistic Discussion: Value of prevalence studies

Prevalence studies provide essential data on how widespread MDD is, allowing governments and health systems to allocate resources and plan interventions effectively.

Holistic Discussion: Strength of combining global and focused studies

Using both global epidemiological data (Global Burden of Disease) and focused meta-analyses (Abdoli et al.) allows both breadth and depth, strengthening conclusions about prevalence patterns.

Holistic Discussion: Limitations of prevalence data

Prevalence rates depend on diagnosis and reporting. Many individuals with MDD may not recognise symptoms, seek help, or disclose distress due to stigma, leading to underestimation.

Holistic Discussion: Cultural influences on prevalence

Cultural norms influence willingness to report symptoms and access mental healthcare. Therefore, observed differences in prevalence may reflect reporting practices as much as true disorder rates.

Holistic Discussion: Explanatory limitations

Prevalence studies describe how common MDD is but do not explain causation. To fully understand MDD, prevalence data must be integrated with biological, cognitive, and sociocultural explanations.

Holistic Discussion: Overall evaluation

Prevalence rates show that MDD is a common and growing global disorder, particularly among women and older adults. While highly informative, prevalence data are most valuable when combined with explanatory research to understand why these patterns exist.