Depression takes its toll worldwide

Depression is more debilitating and harmful to a person’s health than asthma, angina, arthritis and diabetes, several news sources reported. In particular, those people with depression in addition to another medical condition suffer the most.

The reports were based on a survey carried out by the World Health Organisation (WHO) of 250,000 people from 60 countries, where people were given a “health score” for questions that they answered on their health and wellbeing. The survey found that those with depression had worse health scores than those with other common medical conditions. The authors suggest that better funding for mental health services is needed and that it should be considered a “public health priority”.

The World Health Survey has examined the prevalence of depression and four other common medical conditions across 60 countries using participants’ responses to questions on health and well being. It is a large study; however care is needed when interpreting and generalising its overall findings to any given population. The main finding of this study was that people with one or more chronic diseases plus depression (i.e. co-morbid depression) had the worst health scores.

Where did the story come from?

Saba Moussavi and colleagues of Department of Measurement and Health Information Systems, WHO, Geneva, Switzerland, Asian Development Bank, Philippines, and London School of Hygiene and Tropical Medicine, London, conducted this research. Funding was provided by WHO. The study was published in the peer-reviewed medical journal, the Lancet.

What kind of scientific study was this?

This was a multinational cross sectional study designed to look into the worldwide health burden of depression, and to examine the impact that it has on health status, both alone and alongside other medical conditions.

The World Health Survey took a representative sample of 60 countries that were “willing and able to participate”. About 245,000 selected participants were interviewed using a standardised survey. The survey asked a series of questions about symptoms that they had experienced over the past 12 months to determine whether they could be diagnosed as having depression, asthma, arthritis or angina. A diagnosis of diabetes was recorded if the participant reported ever being diagnosed (only asked in 46 of the 60 countries).

The measure of health status was based on a 100 point score derived from 16 self-reported health questions (0 indicating worst health, and 100 indicating best health). The questions assessed the following health domains; vision, mobility, self care, cognition, interpersonal activities, pain and discomfort, sleep and energy, and affect. Participants were given an overall health status score depending on how they responded to the questions about these domains.

Using the survey’s results, researchers then looked at the prevalence of the conditions, alone or in combination with depression, and then looked at the average health score for these groups taking into account other factors such as age, sex and income.

What were the results of the study?

The researchers found that, across all the countries combined, the average prevalence of the five conditions ranged from 2% for diabetes to 4.5% for angina. The prevalence of depression alone (without other illness) was low, at 3.2%.

They found that depression was often present in people with the other medical conditions. Averages for depressed people also having a medical condition ranged from 9.3% in people who also had diabetes up to 23% in those with two or more of the conditions. Overall, they found that depression was more common in the presence of one or more of the other chronic diseases (asthma, angina, arthritis or diabetes).

When examining health scores, they found that on average, the best health scores were in those without either depression or the other chronic illnesses. People with depression were found to have worse health scores than those with only one of the physical conditions. However, the worst scores were in people with two or more of the chronic physical conditions or with two or more chronic conditions plus depression.

What interpretations did the researchers draw from these results?

The researchers find that the prevalence of the chronic conditions examined are similar. However, they conclude that, compared to the chronic conditions asthma, angina, diabetes, and arthritis (on their own), depression (on its own) causes the greatest detriment to health.

However, the worst health was experienced by those who had depression in addition to one of these chronic illnesses.

The researchers suggest that their findings “indicate the urgency of addressing depression as a public health priority to reduce disease burden and disability.”

What does the NHS Knowledge Service make of this study?

This was a large global study that examined the health status and medical conditions of a large number of people across many countries. The following important points should be considered when interpreting it’s results:

• This study has collectively reported the results from all 60 countries grouped together. The prevalence of different diseases and the reporting of them is likely to be variable between individual countries, and as the researchers acknowledge, there may be cultural differences in the way people report their symptoms.
• The survey relies on the participants self-reporting their medical conditions; this may have  introduced some inaccuracies.
• The measure of health status was developed by the World Health Organisation and we must remember that it provides a subjective measure of how people view their health and their difficulties in certain areas. The questionnaire has been tested in a previous study and performed fairly well.
• The study only looked at the effect on health and well being of only four chronic physical conditions combined with depression. Additionally, it did not consider the length of time that an individual had been suffering from the illness. People suffering from osteoarthritis for the past 40 years would be expected to experience far worse related disability than those who have started to have problems within the past year only.
• A person with depression may be in a more negative frame of mind and so could generally have a more negative overall response to questions. Although the study’s authors used a method designed to take this effect into account, there is the possibility that this may still have skewed the results.

This study highlights the significant health burden associated with depression, and the need for it’s proper acknowledgment and appropriate care within the medical profession.

Sir Muir Gray adds...

This study found what previous studies such as the WHO global burden of disease study and the Department of health's own study in 1978 concluded; that for individuals and society, mental health problems and particularly depression, are major causes of suffering.