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Mental illness among adults

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This chapter discusses the prevalence of mental disorders among adults, trends over time, risk factors and consequences.

This chapter discusses the prevalence of mental disorders among adults, trends over time, risk factors and consequences.


Key points 

  • Between one in six and one in four people will suffer from a mental disorder over the course of a year. 
  • Mental disorders and substance use disorders often occur at the same time. 
  • We know little about the individual causes, but both genetic and environmental factors increase risk of developing a mental illness. 

About mental disorders 

The term ‘mental disorder’ refers to a wide variety of conditions and diagnoses. International diagnostic criteria are regularly revised as scientific evidence is updated (First, 2017). Mental disorders are diagnosed by doctors and psychologists using structured clinical interviews. 

Background data 

In this chapter, we have used systematic literature searches and registry data analysis. The registry data were obtained from the Norwegian Patient Registry (NPR), the Norway Control and Payment of Health Reimbursement (KUHR) Database and the Norwegian Prescription Database (NorPD). 

There have been no national diagnosis-based population surveys in Norway. However, two older regional surveys and a survey of a sample of twins have been published (see Table 1). In 2019, a diagnosis-based survey will be conducted among adults aged 20-65 in the county of Nord-Trøndelag. This survey, a collaboration between the Norwegian Institute of Public Health and the Health Survey in Nord-Trøndelag (HUNT), is a pilot for a national survey. 

Prevalence of mental disorders among adults 

Over the course of 12 months, around 16-22 per cent of the adult population will experience a mental disorder (Table 3). The most common mental disorders among adults are anxiety disorders, depression, and substance use disorders; see the chapter on Substance use disorders. 

Phobias are the most common type of disorder. These concern specific situations such as fear of dentists, heights, the dark, enclosed spaces, animals or blood. 

Tables 3 and 4 show the 12-month and lifetime prevalence of the various disorders, respectively. 

  • Around 15 per cent of people will have an anxiety disorder over the course of a year. 
  • About one in ten people will have a depressive disorder over the course of a year. 
  • Approximately 1-3.5 per cent of people will have a psychotic disorder during their lifetime (Perala, 2007; Kringlen, 2001).   

Indicators of lifetime prevalence are unreliable because people have limited recall of psychiatric symptoms, resulting in under-reporting of earlier disorders. 

Half of those with mental disorders have at least two mental disorders 

In the Oslo survey conducted from 1994 to 1997, it was estimated that 11.9 per cent of the population would experience two mental disorders during their lifetime, while 14.9 per cent would have three or more (Kringlen, 2001).  

  • Over a 12-month period, almost half of those who have a mental disorder will also experience one or more other mental disorders, according to a German study (Jacobi, 2015). 

Comorbidity between anxiety and depression is particularly strong (Kessler, 2005; Jacobi, 2015). There is also high comorbidity between mental disorders and substance use disorders (Hasin, 2015). Comorbidity is probably due to the effect of the same causal factors  in different disorders (Krueger, 2006). 

Seeking help from healthcare services 

A significant proportion of the population between 18 and 79 years of age is in contact with healthcare services each year due to psychological symptoms and mental disorders (Figure 1). In 2015: 

  • Ten per cent of all men and 15 per cent of all women was in contact with the primary health service (GPs/emergency medical clinics) as a result of mental problems. 
  • Four per cent of all men and six per cent of all women were in contact with the primary healthcare services (GPs/emergency medical clinics) as a result of mental health problems. 
diagram
Click to enlarge. FHI/NIPH.

Figure 1: Proportion of the population aged 18–79 years registered with psychological symptoms and mental health disorders in the primary healthcare service (blue lines), and mental disorders and behavioural disorders in specialist health services (red lines), 2008–2015. Men - left, women - right.

The proportion who contacted the primary healthcare service regarding mental disorders remained relatively stable during the period 2008-2015. Depressive disorders and anxiety disorders are the most common reasons why those with a mental disorder seek medical attention in the primary healthcare service. 

Many people with mental disorders do not seek help 

Studies from both Norway and elsewhere show that many of those who have mental disorders have not sought medical help (Layard, 2006; Moussavi, 2007; Torvik, 2017). 

The results of the Norwegian Institute of Public Health’s twin study, combined with data from the primary and specialist healthcare services,  found that (Torvik, 2017): 

  • 1 in 3 people who reported that they had depression had also been diagnosed with depression by a GP or emergency medical clinic. 
  • 1 in 7 people who reported that they had depression had also been diagnosed with depression by specialist healthcare services. 
  • Among those who reported having anxiety, 21 and 17 per cent were registered as having anxiety by the primary and specialist healthcare services, respectively. 
  • Among those reporting alcohol abuse, only 3 and 7 per cent were registered as having alcohol abuse problems by the primary and specialist healthcare services, respectively. 
  • Some had received treatment for other mental disorders than the self-reported disorder.  

The Health Survey in Nord-Trøndelag found that 13 per cent of those with symptoms of depression and 25 per cent of those with symptoms of anxiety had sought help (Roness, 2005). The percentage was lowest among those with both depression and anxiety (Roness, 2005). 

Failure to seek help is also a challenge among adolescents. Even among those with the most severe symptoms, only half have sought help for their mental disorder (Zachrisson, 2006). These figures correspond with results from other countries (Kessler, 2005b; Wang, 2005; Alonso, 2004; Klein Berg, 2013; Hämäläinen, 2004; Hasin, 2007). 

Little is known about the degree of treatment coverage for patients with mental disorders in Norway.  This is mainly because there have been no nationwide representative studies of the prevalence of mental disorders among the population. Although we have a relatively good overview of treatment of mental illness by GPs and emergency medical clinics, we have no overview of the number of people who receive other services in the primary health service (such as services from municipal psychologists and psychiatric nurses). 

Drug treatment 

The treatment of mental disorders using prescription medications has remained stable over the past ten years. For anxiety disorders, there has been a shift from reliance on traditional anxiolytics towards greater use of antidepressants in line with recent recommendations. Nevertheless, a high proportion of patients are still treated with addictive anxiolytic benzodiazepines. 

  • Drug consumption for mental disorders increases with age. This is most pronounced for traditional anxiolytics. 

There are major geographical differences in the medical treatment of mental disorders. In general, southern and eastern Norway have the highest prevalence of drug treatment. Figure 2 shows purchases of antidepressants in the various counties. 

map regions
FHI/NIPH

Figure 2: Percentage who were prescribed antidepressants (ATC code N06A) by a pharmacy at least once during 2015. Men and women by county. The figures have been adjusted for different age distributions between the counties. Map basis: Norwegian Mapping Authority. NIPH.. 

Trends 

Several factors suggest that the prevalence of mental disorders is increasing: an increase in the proportion of new disability pensions due to mental disorders in recent years (Mykletun, 2009; NAV, 2018), a slight increase in sickness absence due to mental disorders (nav.no), and a sharp rise in the treatment of mental disorders (Kessler, 2005b; Research Council of Norway, 2009; SINTEF, 2007). 

  • However, most studies that have compared the prevalence of mental disorders among the population over time have found no evidence of any increase (Kessler, 2005b; de Graaf, 2012; Baxter, 2014). 

One exception is a Finnish study that showed how the prevalence of depression among women increased from 2000 to 2011. No corresponding increases were found among men (Markkula, 2015). In this study, the same people were monitored with repeated interviews over an 11-year period. For those who did not participate in the repeated interviews, information was obtained from health registries (Markkula, 2015). 

The results of questionnaire surveys provide no strong evidence of any increase in the proportion that report significant disorders. 

  • The proportion of people reporting significant mental disorders fell from 1998 to 2005, but rose somewhat through to 2012. This is indicated by figures from Statistics Norway's annual surveys among adults (Norgeshelsa). 
  • Among young people aged 16-24 years, there appears to be an increase in the proportion who reported significant mental disorders during the period 1998 – 2012. This increase was greatest among young women (Norgeshelsa). 

In order to determine trends in mental illness in Norway over time, further research with a better background data set than is currently available is needed. 

As the population increases, the absolute number of people with mental disorders will rise (Baxter, 2014). 

Differences between groups in the population 

Differences between age groups: 

Limited information is available about the prevalence of mental disorders in different age groups in Norway but several international studies have shown that it is higher among young adults than among the elderly. 

Two European studies have shown that the 12-month prevalence of mental disorders was about twice as high among adults aged under 34 years than among people aged 65 or older (Alonso, 2004b; Jacobi, 2015). 

In the Oslo Study, people between the ages of 30 and 39 were at greater risk of having a mental disorder than younger and older adults. However, in Sogn and Fjordane, there was no clear link between age and prevalence (Kringlen, 2006). 

Gender differences: 

  • From adolescence onwards,  prevalence of anxiety disorders and depression (point- and 12-month prevalence) is about twice as high among women as among men (Alonso, 2004b; APA, 2013; Baxter, 2013, Ferrari, 2013). 
  • For alcohol-related disorders (abuse and addiction), the pattern is the opposite, with prevalence among men being almost twice as high as that among women. 

This pattern was found in studies in both Europe (Alonso, 2004b) and the USA (APA, 2013). 

For the most severe mental disorders, there is no gender difference in the prevalence of schizophrenia (Perala, 2007; Saha, 2005; McGrath, 2008) or bipolar disorder (Perala, 2007; DiFlorio, 2010). 

Risk factors 

Genetic factors 

Results from twin and adoption studies show that genetic factors have an impact on the development of mental disorders. 

Environmental risk factors 

Environmental factors have an impact on the development of mental disorders. These factors include interpersonal, economic and socio-structural factors (Bronfenbrenner, 1986). 

Unemployment and financial difficulties 

People with a low socioeconomic status are at greater risk of developing mental disorders (WHO, 2014). Mental disorders can cause problems with education and employment, and thus low socioeconomic status. Meanwhile, financial difficulties and employment problems can increase the risk of mental disorders. 

In Spain, an increase in the prevalence of mental disorders was seen during the financial crisis that began in 2007 (Gili, 2013). This was partly explained by unemployment and consequent problems associated with coping with mortgage repayments (Gili, 2013). 

Results from British studies have indicated a correlation between the prevalence of psychiatric disorders and receiving demands for overdue payments (Meltzer, 2013). This may be because unpaid debts impact on mental health, but people with mental disorders are also more likely to be unable to repay debts compared to individuals without mental disorders (Meltzer, 2013). 

Difficulties with interpersonal relationships 

People who experience loneliness, humiliation, bullying or major interpersonal conflict are at greater risk of developing mental disorders such as anxiety and depression (Segrin, 2001; Breivik, 2017; Kendler, 2002; Kendler, 2003; Sourander, 2007). People who are separated are also at greater risk of developing mental disorders than those who are married (Amato, 2010). 

Stress and trauma 

Stressful life events and trauma increase the risk of mental disorders (Kendler, 2016; Kessler, 1997; Amstadter, 2013). These include assault, rape and war, losing a job, or the death of a close family member or friend. 

Neglect and sexual, physical or emotional abuse during childhood are other risk factors for the development of mental disorders such as anxiety, depression, bulimia, personality disorders, and schizophrenia (Kendler, 2000; Carr, 2013). 

Consequences and challenges 

Mental disorders are an important cause of years lived with disability.  

Results of burden of disease analyses indicate that mental disorders and substance use disorders were important causes of non-fatal health loss in Norway in 2016, as measured by YLD (Years Lived with Disability) (https://vizhub.healthdata.org/gbd-compare). When disorders are split into smaller categories, depressive and anxiety disorders are in third and fourth place in the list of causes of YLD, respectively (NIPH 2017). Their high position in the list is partly due to their high prevalence and partly due the health loss associated with these disorders.

Schizophrenia was at 17th and bipolar disorder at 21st place in the list of top causes of YLD in Norway in 2013. These diseases are rare  but they have major consequences for those affected (NIPH, 2016). 

  • Mental disorders are particularly important causes of health loss among the population under 50 years of age, affecting therefore those of reproductive and working age. 

Sick leave and disability benefit 

Reduced work capacity is a common and serious consequence of mental disorders. 

  • Anxiety and depression contribute most to sickness absence (Henderson, 2005). 
  • Symptoms of anxiety and depression are associated with both repeated and prolonged periods of sickness absence (Knudsen, 2013). 

The average age at which disability benefit due to mental disorders is given is lower than for other disorders (Mykletun, 2009). In 2014: 

  • Mental disorders were the main diagnoses for 36.8 per cent of those who received a disability benefit. 
  • In comparison, musculoskeletal and cardiovascular diseases (e.g. myocardial infarction) were the main diagnoses for 26.6 per cent and 5.1 per cent respectively of those given a disability benefit. 

Anxiety and depression also increase the likelihood of a disability benefit for a somatic condition (Mykletun, 2006; Knudsen, 2010). 

In Norway, the work participation rate among people with schizophrenia at working age is about 10 per cent (Evensen, 2016). This proportion is roughly equal for both sexes and across all ages. 

A recent Norwegian study found that good follow-up increases workplace participation for individuals with schizophrenia (Falkum, 2017). 

Somatic disorders and mortality 

Mental disorders are associated with an increased risk of physical disorders and premature death. This may be explained by the relationship between mental disorders and the increased tobacco and alcohol consumption, poor diet, overweight and physical inactivity, which are all risk factors for cardiovascular disease, cancer, diabetes and chronic lung diseases. 

People with mental disorders are at greater risk of committing suicide (Walker, 2015; Nordentoft, 2013; Mental Health Foundation, 2016; Scott, 2011; Wahlbeck, 2011; Chesney, 2014). 

  • The life expectancy of individuals with schizophrenia or bipolar disorder is 10-20 years shorter than that for the general population (Laursen, 2011; 2013). 

People with depression or anxiety also have higher mortality rates compared with the general population (Walker, 2015; Laursen, 2016). 

Two Norwegian studies have found that health anxiety is associated with increased likelihood of cardiovascular disease among men and women, and with cancer among men (Berge, 2016; Knudsen, 2015). Anxiety can therefore have negative consequences for somatic health but can also result in health-care seeking behaviour, thereby resulting in early diagnosis of diseases. 

Prevention 

To prevent and reduce the severity of mental health disorders in the general population and improve subjective quality of life and well-being, preventive measures should be implemented to reduce stress and vulnerability and promote conditions that have a positive impact on the health of the general population. 

The foundation for mental health and quality of life for the adult population begins in childhood and adolescence. 

This relies, in part, upon the creation of social environments where children and adolescents are not subject to bullying or social exclusion and where everyone is part of a positive social environment providing opportunities to experience mastery and engagement (Mental Health in Norway). 

In addition, special intervention measures targeting adults and the elderly are required. Important arenas are higher education institutions, the workplace, local communities, volunteer programmes, , health and social services, and institution for the elderly.

Citation

Cite this article as: Mental illness among adults in Norway. In: Public Health Report - Health Status in Norway [online document]. Oslo: Institute of Public Health [updated (insert date); read (insert date)]. Available from: (insert link).

Tables

Table 1. Norwegian and international epidemiological studies

Study

Country

Year

Participants

Interview manual

Diagnostics

manual

Norwegian Twin Registry

Norway

1999-2004

2 801

Age: 19-36

CIDI

DSM-IV

Oslo study

Norway  (Oslo)

1994-1997

2 066

Age: 18-65

CIDI

DSM-III-R

Sogn og Fjordane
County study

Norway
(Sogn og Fjordane County)

1997-1999

1 080

Age: 18-68

CIDI

DSM-III-R

National Comorbidity
Survey (NCS)

 

USA

1990-1992

8 098

Age 15-54

CIDI

DSM-III-R

National Comorbidity
Survey Replication (NCS-R)

 

USA

2001-2003

9 282

Age: 18+

CIDI

DSM-IV

Netherlands Mental Health
Survey and Incidence Study (NEMESIS)

 

Netherlands

1996

7 076

Age: 18-64

CIDI

DSM-III-R

Netherlands Mental Health
Survey and Incidence Study -2 (NEMESIS-2)

 

Netherlands

2007-2009

6 646

Age 18-64

CIDI

DSM-IV

The European Study of Epidemiology of Mental
Disorders project (ESEMeD)

Belgium, France, Germany, Italy, Netherlands and Spain

2001-2003

21 425

Age: 18+

CIDI

DSM-IV

The Health 2000 Study

Finland

2000-2001

6 005

Age: 30+

CIDI

DSM-IV

The Health 2011 Survey

Finland

2011

4 478

Age: 30+

CIDI

DSM-IV

German Health Interview and Examination Survey for Adults – Mental Health (DEGS1-MH)

 

Germany

2009-2012

5 303

Age: 18-79

DEGS-CIDI

DSM-IV

The Canadian Community Health Study – Mental Health (CCHS-MH)

 

Canada

2012

25 113

Age: 15 +

CIDI

DSM-IV

The National Epidemiologic Survey on Alcohol and related Conditions (NESARC) – Wave 1

USA

2001-2002

43 093

Age: 18+

AUDADIS-IV

DSM-IV

The National Epidemiologic Survey on Alcohol and related Conditions (NESARC) – Wave 2

USA

2004-2005

34 093

Age: 20+

AUDADIS-IV

DSM-IV

Dunedin Multidiciplinary Health and

Development Study

New Zealand

1990-2005

1000

Age: 18-32

DIS-III/ DIS-IV

DSM-III-R/ DSM-IV

 

Table 2. 12 month prevalence (%) among adults, Norwegian and international studies.

Disorder

Oslo

S Fj

NCS

NCS-R

NEMESIS

NEMESIS-2

ESEMeD

Health 2000

Health

2011

DEGS1-MH

CCHS-MH

NESARC 1

Dune-din

Anxiety disorders

 

 

17,2

18,1

12,4

10,1

6,4

 

 

15,4

 

11,1

22,8

Specific phobia

11,1

5,0

8,8

8,7

7,1

5,0

3,5

 

 

10,3

 

7,1

7,2

Social anxiety disorder

7,9

5,0

7,9

6,8

4,8

3,8

1,2

1,0

 

2,8

 

2,8

10,8

Agoraphobia

3,1

1,6

2,8

0,8

1,6

0,4

0,4

1,2

 

4,0

 

0,1

 

Panic disorder

2,6

1,2

2,3

2,7

2,2

1,2

0,8

1,9

 

2,0

 

2,1

1,8

Generalized anxiety disorder

1,9

1,1

3,1

3,1

1,2

1,7

1,0

1,3

 

2,3

2,6

2,1

4,2

Obsessive-compulsive disorder (OCD)

0,7

0,3

 

1,0

0,5

 

 

 

 

3,6

 

 

 

Depression and bipolar disorders

 

 

11,3

9,5

7,6

6,1

4,2

 

 

9,8

 

 

 

Major depressive disorder (MDD)

7,3

3,7

10,3

6,7

5,8

5,2

3,9

4,9

7,4  (5,4)*

6,8

3,9

5,3

16,7

Dysthymia

3,8

1,6

2,5

1,5

2,3

0,9

1,1

2,5

4,5 (2,0)*

1,7

 

1,4

 

Bipolar disorder

0,9

0,1

 

2,6

1,1

0,8

 

 

 

1,5

 

2,0**

 

Non-affective psychosis

0,2

0,3

0,5

 

 

 

 

 

 

 

 

 

 

Schizophrenia

 

 

 

 

0,2

 

 

 

 

 

 

 

 

Other disorders

 

 

 

 

 

 

 

 

 

 

 

 

 

Somatoform disorders

2,1

2,2

 

 

 

 

 

 

 

 

 

 

 

Eating disorders

0,7

0,1

 

 

0,4

 

 

 

 

0,9

 

 

 

*Persons with mental disorders are underrepresented in this study, therefore figures are adjusted according to information from national registries. Unadjusted figures in parenthesis.  ** Bipolar type 1.

Table 3.  Lifetime prevalence (%) among adults, Norwegian and international studies.
Lidelse

Oslo

S og Fj

Tvilling

NCS

NCS-R

NEMESIS

NEMESIS-2

ESEMeD

CCHS-MH

NESARC 1

Dunedin

Anxiety disorders

 

 

26,7

24,9

28,8

19,3

19,6

13,6

 

17,2

49,5

Specific phobia

14,4

6,5

18,6

11,3

12,5

10,1

7,9

7,7

 

9,4

18,8

Social anxiety disorder

13,7

7,3

4,0

13,3

12,1

7,8

9,3

2,4

 

5,0

27,9

Agoraphobia

6,1

3,6

4,8

5,3

1,4

3,4

0,9

0,9

 

0,2

 

Panic disorder

4,5

2,6

2,8

3,5

4,7

3,8

3,8

2,1

 

5,1

6,5

Generalized anxiety disorder

4,5

3,4

2,0

5,1

5,7

2,3

4,5

2,8

8,7

4,1

14,2

Obsessive-compulsive disorder (OCD)

1,6

0,6

0,7

 

1,6

0,9

 

 

 

 

 

Depression and bipolar disorders

 

 

 

19,3

20,8

19,0

20,2

14,0

 

 

 

Major depressive disorder (MDD)

17,8

8,3

14,0

17,1

16,6

15,4

18,7

12,8

9,9

13,2

41,4

Dysthymia

10,0

6,3

1,7

6,4

2,5

6,3

1,3

4,1

 

3,2

 

Bipolar disorder

1,6

0,2

 

 

3,9

1,8

1,3

 

 

3,3*

 

Non-affective psychosis

0,4

0,4

 

0,7

 

 

 

 

 

 

 

Schizophrenia

 

 

 

 

 

0,4

 

 

 

 

 

Other disorders

 

 

 

 

 

 

 

 

 

 

 

Somatoform disorders

3,7

3,4

 

 

 

 

 

 

 

 

 

Eating disorders

1,8

0,5

1,7

 

 

0,7

 

 

 

 

 

* Bipolar type 1.

References

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