Prospective associations between major depressive disorder, generalized anxiety disorder, fibromyalgia, and myalgic encephalomyelitis/chronic fatigue syndrome.
Thomas, Nathaniel Stembridge, Neale, Michael C, Kendler, Kenneth S et al. · Psychological medicine · 2025 · DOI
Quick Summary
This study followed over 100,000 people over time to understand how depression, anxiety, fibromyalgia, and ME/CFS relate to each other. The researchers found that these conditions tend to be connected, but the direction of the connection varies: fibromyalgia appears to lead to depression, while ME/CFS and depression seem to influence each other in both directions. The study suggests that these conditions should be studied separately rather than grouped together, since they may work differently.
Why It Matters
Understanding whether ME/CFS causes depression or vice versa—or whether they influence each other mutually—is crucial for developing targeted treatments. This study provides evidence that ME/CFS may have a bidirectional relationship with mood disorders, suggesting that treating one condition may help the other, and that patients experiencing both deserve integrated care approaches.
Observed Findings
Functional disorders (FM and ME/CFS) showed greater stability over time than internalizing disorders (MDD and GAD).
Fibromyalgia predicted the development or worsening of major depressive disorder in a unidirectional pattern (β=0.14).
ME/CFS demonstrated bidirectional associations with both MDD and GAD, suggesting mutual influence.
Initial comprehensive models supported mostly bidirectional relationships between internalizing and functional disorders.
Functional disorders were more commonly present than internalizing disorders at baseline.
Inferred Conclusions
Fibromyalgia and depression may have a unidirectional causal relationship, with fibromyalgia potentially causing or exacerbating depression.
ME/CFS appears to have a bidirectional relationship with mood disorders, meaning depression and anxiety may both result from and contribute to ME/CFS symptoms.
Functional disorders should be studied as distinct conditions rather than lumped together, as they show different patterns of association with psychiatric symptoms.
The relative stability of functional disorders suggests they may be primary drivers of psychological distress in some cases.
Remaining Questions
What are the biological mechanisms underlying the unidirectional effect of fibromyalgia on depression versus the bidirectional relationship between ME/CFS and mood disorders?
What This Study Does Not Prove
This study demonstrates associations over time but cannot definitively prove causation; the bidirectional relationships could be explained by shared underlying biological mechanisms or unmeasured factors. The results are 'consistent with' a causal link from fibromyalgia to depression but do not conclusively establish it. Additionally, findings from a Dutch population-based cohort may not generalize to all ME/CFS populations, particularly those with more severe disease.
Tags
Symptom:PainFatigue
Method Flag:PEM Not DefinedWeak Case DefinitionMixed Cohort
Can these findings be replicated in different populations, particularly in more severely affected ME/CFS patients or those diagnosed through specialized clinics?
To what extent do shared genetic or environmental factors explain the associations observed, and how much is due to direct causal effects?
Do interventions targeting one condition (e.g., treating depression in ME/CFS) effectively reduce symptoms of the other, and does the directionality of the relationship predict treatment response?