Psychiatric disorders and the onset of self-reported fibromyalgia and chronic fatigue syndrome: The Lifelines cohort study

Objective:  This study aimed to assess whether psychiatric disorders predict onset of fibromyalgia and chronic fatigue syndrome (CFS) which develop in the presence of pre-existing muscle pain or fatigue. 
Methods: The population-based Lifelines cohort study included 148,614 adults with relevant data for the fibromyalgia study and 136,423 for the CFS study. Participants with prior self-reported fibromyalgia (or CFS) at baseline were excluded from the relevant analysis. At follow-up (mean 2.4 years) new onsets of each syndrome were identified by self-report.  Logistic regression was used to identify which of the baseline variables predicted new onsets of each syndrome. Prior to the analyses the samples were divided into those with and without marked muscle pain (for fibromyalgia analysis) or persistent fatigue (for CFS). 
Results. During follow-up there were 692 (0.5%) new onsets of self-reported FM in participants without marked muscle pain and 281 (3.75%) in those with such pain; for CFS it was 296 (0.2%) for those without and 192 (1.9%) for those with baseline fatigue. In univariate analysis psychiatric disorder was associated with onset of both FM and CFS but in logistic regression psychiatric disorder was a predictor only in the CFS-onset group who had persistent baseline fatigue.  
 Conclusion. Despite its limitations this study suggests that psychiatric disorders do not predict self-reported fibromyalgia but do predict CFS when there is pre-existing persistent fatigue. Progress in understanding the aetiology these disorder may require understanding the risk factors for severe muscle pain and fatigue rather than relying on diagnostic categories of established cases.

Abbreviations: FM= fibromyalgia,  IBS= Irritable bowel syndrome,  , CFS = chronic fatigue syndrome,  OR =Odds Ratio, SCL= Symptom checklist, PSQI = Pittsburgh Sleep Quality Inventory.