Multiple physical symptoms and coping in the Danish general population

Many people frequently experience symptoms like abdominal pain, headache, dizziness, and tiredness. Although most symptoms are mild and self-limiting, a minority become recurrent or persisting. This can impair physical and mental health, leading to reduced quality of life and increased levels of sick leave and disability pension. There is not always an obvious explanation for symptoms, and hence they can be termed functional somatic symptoms in this PhD project, it has been challenging to determine alternative causes for the symptoms, and therefore the term “multiple physical symptoms” has been used to describe individuals bothered by four somatic symptoms regardless of etiology.

The etiology of multiple physical symptoms is often described within the bio-psycho-social model which emphasizes that biological, psychological, and social factors are important for the development of symptoms. The complex etiology and the lack of simple treatment options make the condition difficult to manage in the healthcare system, particularly in general practice where most consultations are restricted to 10–15 minutes.

Although a great deal of research within symptom disorders has been conducted in past years, most research is conducted in specialized settings, while only a small proportion is conducted in the general population. It is known from previous studies that the way people react in relation to symptoms (i.e., coping with symptoms) can maintain symptoms. Yet knowledge is lacking about whether the way people usually react to stress and difficult situations (i.e., general coping), is associated with the development and persistence of symptoms in the general population. It is particularly interesting to examine whether certain types of coping strategies together with sociodemographic variables such as sex, age, educational level, and ethnicity are associated with the development and persistence of symptoms.

These questions have been answered in this thesis, based on questionnaire data combined with register data. In 2012, a total of 100,000 Danish citizens aged 20 years or older were randomly selected from the civil registration system and invited to participate in a survey about symptom experiences and healthcare seeking as part of the Danish Symptom Cohort (DaSC). In 2022, a new random sample of 100,000 citizens aged 20 years or older were invited to participate in a follow-up survey. The survey questionnaires included a checklist of 25 symptoms and a brief coping scale, measuring approach and avoidance coping.

Study 1 included nearly 36,000 individuals aged 20 to 64 years who participated in the DaSC survey in 2012. Study 1 showed that individuals with multiple physical symptoms had lower scores on approach coping strategies such as “I make an active effort to find a solution to my problems” and “I think something positive could come out of my problems.” At the same time, these individuals had higher scores on avoidant coping strategies such as “I put my problems behind me by concentrating on something else” and “I withdraw from other people when things get difficult.” Similar results were found in Study 2, which included around 18,000 individuals aged 20 to 64 years who participated in the DaSC II survey in 2022. Study 3 included around 16,000 individuals from Study 1 who also participated in the DaSC II survey in 2022, thus providing 10-year follow-up data. Study 3 showed that individuals who developed and maintained multiple physical symptoms over the decade had higher baseline scores on avoidant strategies and lower baseline scores on approach strategies compared with other individuals in the Danish general population. These results indicate that the way people in the general population respond to stress and difficult situations in their everyday lives can affect the development and persistence of symptoms and in this respect, avoidance seems less beneficial.

In a comparison of the two cross-sectional samples from Study 1 and 2, it appeared that more participants fulfilled the criteria for MPS in 2022 compared with 2012. The results also showed that the coping scores were slightly different in the two samples, with lower scores for approach and higher scores for avoidance.

Knowledge about the symptom burden in the Danish population is valuable when organizing the future healthcare system, and the results of this thesis point to a need for greater capacity in specialized centers. Additionally, early interventions are needed to prevent milder cases progressing to severe cases. In this respect, knowledge about coping in the general population could be beneficial to provide earlier and better treatment to individuals experiencing multiple physical symptoms.