Researchers very comprehensively studied the trends in diagnosed mental health disorders in Denmark over many years. A researcher says that this provides a basis for discussing how to improve mental health.
The incidence of mental health disorders has been increasing in many countries in recent years, including anxiety, depression, mood disorders, eating disorders, schizophrenia and bipolar disorder. Researchers carried out the most comprehensive study ever of the incidence in Denmark.
The survey found that both younger men and younger women develop more mental health disorders than other generations, and people are diagnosed at specific periods in life.
The results also indicate surprising trends: in recent years, almost as many young women as young men have been diagnosed with schizophrenia.
According to a researcher behind the study, the results can help politicians and decision-makers to focus on areas in mental health services requiring intervention.
“Mental health disorders are much in focus in Denmark today, and this focus should remain strong. These data show that young people not only more often develop mental health disorders but are often afflicted during a vulnerable period of their lives, having young children and entering the labour market, when good mental health is important,” explains Oleguer Plana-Ripoll, Associate Professor, Department of Clinical Medicine, Aarhus University, Denmark.
The research has been published in JAMA Psychiatry.
Detailed analysis is important
The researchers aimed to analyse the data on the mental health of people in Denmark and the trends over time in more detail. They therefore investigated the trends in eight birth cohorts: 1924–1939, 1940–1949, 1950–1959 and further cohorts up to 2011.
The researchers also examined the incidence of mental health disorders in six three-year periods from 2004 to 2021.
Oleguer Plana-Ripoll explains that the birth cohorts indicate the incidence of mental health disorders among people born at a given time, and the differentiation by three-year periods shows how a specific time period can be associated with better or worse mental health and thereby the incidence of mental health disorders.
For example, events such as wars and pandemics may affect how many people develop a mental health disorder across all birth cohorts.
“Few studies have examined all the numbers. When mental health disorders increase over time, we can have difficulty in discerning whether this results from a cohort effect or particular events in a specific period. Separating these can be difficult, which is why we aimed to provide numbers for both: how this manifests in the birth cohorts, in three-year periods and between the sexes,” says Oleguer Plana-Ripoll.
The research was carried out using anonymised data from the extensive registries covering the entire population of Denmark, and individuals cannot be identified.
Increasing number of mental health disorders
The data reveal an increase in mental health disorders over time for both birth cohorts and three-year periods.
Overall, most mental health disorders are diagnosed when people are 5–40 years old.
The highest number of mental health disorders are diagnosed at 15–20 years old, with up to 250 new mental health disorders per 10,000 person-years for women born in 2000–2009 versus about 125 new mental health disorders per 10,000 person-years for women born in 1980–1989.
Similarly, there were slightly more than 250 new mental health disorders per 10,000 person-years for women 15–20 years old in 2019–2021 versus about 125 new mental health disorders per 10,000 person-years for women 15–20 years old in 2004–2006.
However, the survey also found no large increase in new mental health disorders among people older than 40 years for birth cohorts or three-year periods.
“However, the numbers for mental health disorders are the ones diagnosed in hospitals, so this does not include all mental health disorders. We only have data about people diagnosed in hospitals and nothing about people treated in municipal care or by their general practitioner,” explains Oleguer Plana-Ripoll.
More women diagnosed with schizophrenia
The survey also reveals other trends, some of which are surprising.
For example, the incidence of substance abuse is similar over time for birth cohorts and across three-year periods for younger people, but not for older people, for whom substance abuse is declining across both birth cohorts and three-year periods.
Perhaps even more surprising is that although men historically have developed schizophrenia more often than women, the numbers seem to have evened out, with men having about the same incidence and women increasing.
Oleguer Plana-Ripoll has several explanations for these results.
“More women could have developed schizophrenia, but I find this hard to believe. Instead, I think that diagnostic practices have changed, so that more women who previously would not have been diagnosed are being diagnosed today. This result is surprising. Other studies have shown a narrowing gap between the sexes, but we did not imagine this level. Investigating this more closely in the future would make sense,” he notes.
Important research resource
According to Oleguer Plana-Ripoll, the results can primarily be used as a resource for other researchers to explore.
Researchers can investigate whether more people develop depression today than previously or whether changing diagnostic practices account for the increases.
People who set policy guidelines within this area can also delve into the numbers and use them to make decisions based on firm evidence.
“Today there is great focus on improving the lives of people with a mental health disorder, but remember that the group of people who develop these disorders is constantly changing. Based on these data, we cannot say why the changes we observe occur, but this will be relevant to investigate in future studies,” concludes Oleguer Plana-Ripoll.
