Changes in prescription of antidepressants and disability pension due to back pain, compared with other musculoskeletal and other somatic diagnoses: a cohort study in Sweden

Low back pain (LBP) constitutes one of the most critical public health problems today.1 Particularly, the chronicity plays an important role in the often long process from onset of disease to becoming work disabled. LBP ranks among the most frequent causes of sickness absence (SA) and disability pension (DP) and covers a clinically heterogeneous patient group from unspecific pain to more specific disorders.1–3 In the ranking of risk factors for disease burden, occupational LBP ranks high although without attributable deaths.4 In addition, LBP and neck pain is the fourth leading cause of the burden of disease measured as loss of disability adjusted life years. This compares to ischaemic heart diseases and cerebrovascular diseases that are the number one and two, respectively, and to depressive disorders at 11th place.5

LBP is strongly interlinked with common mental disorders (ie, depressive and anxiety disorders),6 7 which may additionally worsen work ability.2 In Europe, up to 30% of subjects with chronic pain (the majority with LBP) have a comorbid depression or anxiety.8 Partially based on the same dataset as in this study, coexisting common mental disorders and LBP increased the risk of granting DP.2 Still, to date the role of common mental disorders in the process to DP has received little scientific interest. Hence, a need exists to elaborate whether worsening mental health is aggravating the disabling process finally resulting in permanent work disability. For example, patterns related to the development of mental health problems in the process to DP might be specific for individuals with LBP or comparable to such patterns in individuals with other musculoskeletal or other somatic disorders. Elucidating any differences between LBP, mental disorders or their mutual effects is therefore warranted.

Although no time trend in depressive symptoms in association with DP has been shown,9 an expectation is that mental health may deteriorate after DP. However, also the opposite might be true, namely that mental health improves after a DP due to LBP as physical and psychological work demands are removed.10 Previous studies on DP due to mental diagnoses suggest a worsening of mental symptoms before DP, after which mental health seems to improve.11 Indicators of mental health such as SA, inpatient or outpatient care due to mental diagnoses,2 12 or use of psychotropic drugs,11 13 14 can be used for assessing the development of mental health before and after granting of DP.

Mental health trajectories following DP might also be related to the severity and progression of the disorder underlying the DP.15 Consideration of disease severity conceptualised by treatment in specialised healthcare is crucial. In specific, individuals seem to seek help for common mental disorders relatively late in the disease trajectory, hence potentially reflecting also the severity of common mental disorders.16 We hypothesised that the prescription of antidepressants would differ not only regarding timing in relation to DP but also with regard to diagnosis for DP and severity of the underlying disease.

This study aimed to investigate (1) if the years preceding and the years following granting of DP due to back pain were associated with changes in prescription of antidepressants, (2) if there were variations in these patterns regarding previous specialised healthcare and (3) if there were differences in comparison to DP due to other musculoskeletal and other somatic than musculoskeletal diagnoses.