Prevalence rates are not simply statistical accounts of how many people suffer from a specific disorder.  They also provide us with information about the nature of disorders.  For example, we sometimes see that there is a difference in the prevalence rates of a disorder in men and women. We also see that different cultures have different levels of a disorder.  For example, McGrath et al (2003) found that the prevalence of schizophrenia varies significantly among cultures, with a median value of 15.2 per 100 000, with a range of 7.7 to 43.

Prevalence rates are also problematic because a diagnosis is not always reliable across cultures.  Symptoms may be different for the same disorder in different cultures.

When applying an etic approach, we may see that another culture exhibits a lower prevalence of a disorder because the symptoms do not align with a standardized checklist.  On the other hand, if we use an emic approach and then attribute a set of symptoms within a culture to a disorder in another culture, this could also be problematic.  For example, if we assume that somatic symptoms are actually signs of depression, this may raise the prevalence rate.  However, is this truly the same disorder that we are seeing in Western psychiatry?

For example, Kleinman (2004) argues that depressed Chinese people do not report feeling sad, but rather express boredom, discomfort, feelings of inner pressure, and symptoms of pain, dizziness, and fatigue. When attempting to diagnose these patients, Western psychiatrists may fail to attribute these symptoms to depression.  On the other hand, with regard to the etiology of depression, we have to question whether this is, in fact, the same disorder.

Prevalence rates are not universal - and they also change over time. There are several arguments about why this may be true, ranging from the way that data is collected, to the level of stigma in society to the role of globalization.

Changes over time

A recent report carried out in the USA  by the George Washington University Milken Institute School of Public Health (2015) showed that the rate of diagnosis of Attention Deficit Hyperactive Disorder [ADHD] has increased by 43% over the past eight years.  Twenge (2014) found that teens in the US are significantly more likely to show signs of depression than their 1980’s counterparts. And research on schizophrenia (Healy et al, 2012)  shows a drop in the number of schizophrenic cases in hospitals. It is clear that prevalence rates are not constant.  Why do they appear to change over time?  There are several factors that could be considered.

When looking at prevalence rates, it is important to consider the environmental factors that may play a role in triggering disorders.  Some environmental triggers are obvious. For example, the Rwandan genocide had a significant impact on the mental health of the average Rwandan. However, we cannot assume that negative environmental conditions will always lead to an increase in mental illness. When considering the economic crises that hit such countries as Greece and Spain in the early 2000s, one would expect to see an increase in mental health problems.  However, the World Health Organization (2011) published a report that showed that there was no clear link between the economic crises and a change in the prevalence of disorders. According to the report, family support, state programs and an increase in the price of alcohol may have all contributed to the stability of prevalence rates.  

Twenge (2015) argues that one of the reasons for an increase in the prevalence of depression among young people is a change in social norms that make a diagnosis of depression less of a stigma. The media may play a role in promoting the need to seek help or to take medication. Prevalence rates are based on reported cases - if there are more people coming forward for help, that will result in a higher prevalence rate.

The case of schizophrenia is an interesting one.  Why might the rate be going down?  There are two potential answers.  An optimistic approach argues that we are now better at identifying and addressing risk factors, thus leading to a lower number of cases.  The more pessimistic argument has to do with how the statistics are gathered.  Healy et al (2012) found that the rate of hospital admissions for schizophrenia has dropped.  This may mean that doctors are less likely to admit patients and that this does not reflect an actual decrease in the prevalence of the disorder – but more about the accessibility of mental health care.

The role of globalization

Today we live in a globalized society.  One of the key arguments for why we see a change in prevalence rates is that cultural groups around the world may change their expression of psychological distress as a result of exposure to media from other cultures.  Ethan Watters writes about this extensively in his book Crazy Like Us.  An example that he gives is the growth of anorexia in Hong Kong.

In Hong Kong, prior to the late 1990s, there were almost no women diagnosed with anorexia nervosa. The prevalence rate was negligible.  There was a similar disorder that existed in which patients wasted away.  Patients often complained that their stomachs felt distended and that they were not hungry. The patients complained of a lack of meaning to their existence, or that they had let down their families and as a result, experienced and relentless sense of shame.  The key difference between this disorder and Western anorexia is that the patients did not have a false perception of their body weight. They were fully aware that they were wasting away but felt unable to stop the process.

Watters argues that it was the death of a popular singer, Charlene Hsu Chi-Ying, that began the increase in the prevalence of the disorder in Hong Kong. Charlene had a heart attack on the metro (subway) in Hong Kong.  When the paramedics went to assist her, they were shocked to find that she was only skin and bones.

This case received high publicity. In order to discuss what happened, Chinese reporters looked to Western experts. The news presented this as a health concern that needed to be addressed. Within a few years of Charlene's death, there were several Hong Kong actresses coming out as anorexic. By 1997 fear of being overweight had become the single most important reason given for self-starvation.  Also, previous somatic signs of the disorder - e.g. distended stomach - no longer were noted.  As time progressed, the prevalence of the disorder increased to a level similar to those seen in Western countries.

In the case of anorexia in Hong Kong, Watters argues that the women are attracted to the "cultural template of behaviour" which shows dysfunction or distress. In other words, when an individual feels psychological distress, the symptoms that one adopts come out of the "symptom pool" that is appropriate for one's culture, age, and gender. Society dictates what the appropriate "illness" is.  As society becomes more globalized, we see a rise in illnesses formerly seen outside of the culture.

The case study that Watters presents describes how Western influence had a major effect on the prevalence of anorexia in Hong Kong.  However, the theory that young women adopt the symptoms of the "cultural template of behaviour" is difficult to test.  The theory cannot be easily falsified and although it may seem reasonable enough, it is not based on an actual empirical study.  That being said, obsession with bodyweight continues to be a problem in China.  The following video from 2016 shows a trend called the A4 challenge. Once again, it spread around the world through social media.

A final concern about globalization is the marketing of pharmaceuticals.  As individuals are exposed to the marketing of drugs that are alleged to improve one's mental health, this may lead to more people seeking out medical advice. This may also increase the reported prevalence of a disorder.

An example of this is the prevalence of Major Depressive Disorder in Japan.  Traditionally, depression was seen as a need for spiritual guidance and/or time with family. The Japanese did not see depression as a "disorder," but rather as a sign that one had to get back to their "moral compass."

 Teacher only box

When considering the pros of Direct to Consumer advertising [DTC], students may come up with some of the following:

• DTC prescription drug ads encourage people to seek medical advice for health problems.
• DTC drug ads inform patients about medical conditions and possible treatments.
• They encourage patient compliance with treatment instructions. Because the patient requests the drug, they are more likely to stick to regularly taking their medication.
• The ads help remove the stigma associated with both the medical condition and the treatment.
• The ads create revenue that can be used for developing better drugs.

When considering the cons of Direct-Consumer advertising, students may come up with some of the following:

• DTC ads may misinform patients. According to a study published in the Sept 2013 issue of the Journal of General Internal Medicine, 60% of claims made in DTC prescription drug ads aired from 2008 to 2010 “left out important information, exaggerated information, provided opinions, or made meaningless associations with lifestyles.” The study found 43% of the claims in DTC drug ads were “objectively true” while 55% were “potentially misleading” and 2% were “false.”
• DTC ads may lead consumers to believe that drug treatment is the only viable form of therapy.
• DTC ads may encourage over-medication.
• Health care professionals may feel pressured to prescribe drugs that may not be in the best interest of the patient.
• Some doctors argue that the ads weaken their relationship with their patients.
• Often this leads to the purchase of "brand name" drugs rather than generic alternatives, driving up the cost of health care.

As for whether this should be allowed or not - that is the discussion to be had with your students!

Checking for understanding

Treatment of disorders