Psychological flexibility in somatic symptom and related disorders: A case control study.

A key diagnostic criterion of Somatic Symptom and related Disorders (SSD) comprises significant distress and excessive time-and-energy consuming thoughts, feelings, and behavior pertaining to somatic symptoms. This diagnostic criterion is lacking in central sensitivity syndromes (CSS), such as fibromyalgia, irritable bowel syndrome, and chronic fatigue syndrome. This strong emphasis on disturbed psychological processing of somatic symptoms, suggests that psychological flexibility is low in SDD. Psychological flexibility is defined as the ability to approach difficult or challenging internal states (thoughts, emotions, and bodily sensations) in a non-judgmental, mindful way, and being committed to pursue one's values. To clarify the potential significance of psychological flexibility in SSD, we examined its levels in 154 people referred to specialized treatment for SDD, as compared to reference groups from the general population encompassing 597 people with CSS and 1422 people without SSD or CSS (controls). Mean levels of psychological flexibility (adjusted for demographic covariates) were lowest for SSD and highest for controls (F = 154.5, p < 0.001, pη2 = 0.13). Percentages of people with low psychological flexibility (<0.8 SD below the mean of controls) were: SSD 74%, CSS 42%, controls 21%. In SSD, higher psychological flexibility was associated with better mental health (ß = 0.56, p < 0.001), but interaction analysis rejected that psychological flexibility preserved health when having more severe somatic symptoms (ß ≤ 0.08, p ≥ 0.10). The results indicate that lower psychological flexibility is a prevalent problem in SSD that is associated with lower mental health. This suggests that it is worthwhile to take account of psychological flexibility in SSD in screening, monitoring, and therapy.

Individual outcomes after tailored versus generic self-management strategies for persistent fatigue in youth with a fatigue syndrome or rheumatic condition: A multiple single-case study.

OBJECTIVE: To examine individual outcomes after tailored lifestyle (PROfeel) or generic dietary advice as self-management intervention for persistent fatigue in adolescents and young adults with a chronic condition, to compare participants who did and did not benefit and to explore changes to factors in the biopsychosocial model of fatigue after PROfeel. METHOD: A multiple single-case AB-phase design was embedded in a randomized crossover trial (N = 45). Intensive longitudinal data (ILD) on outcomes 'fatigue severity', 'self-efficacy' and 'quality of life' (QoL) were collected through weekly smartphone measurement for 20 weeks. ILD on biopsychosocial factors were collected through experience sampling methodology for 28 days pre-post first intervention. Baseline characteristics were compared with t-tests and chi-square tests. Permutation distancing tests were used to assess change over time in all ILD. RESULTS: Regarding weekly measurements, nineteen participants (42.22%) showed small to large positive outcomes (drange = .05 to 2.59), mostly after PROfeel. Eleven participants (24.44%) showed small to moderate negative outcomes (drange = -.02 to -2.46), mostly after dietary advice. Fatigue severity improved most, followed by self-efficacy. Participants who benefitted showed higher QoL levels and lower fatigue and pain levels compared with others at baseline (all p < .02). When positive outcomes were observed after PROfeel, typically ≥1 biopsychosocial factor had been targeted successfully. CONCLUSION: Self-management advice has more potential when tailored to individual characteristics, including the biopsychosocial model of fatigue. PROfeel appears particularly useful as fatigue intervention for individuals with relatively less severe symptoms.

The Permutation Distancing Test for dependent single-case observational AB-phase design data: A Monte Carlo simulation study.

The Permutation Distancing Test (PDT) is a nonparametric test for evaluating treatment effects in dependent single-case observational design (SCOD) AB-phase data without linear trends. Monte Carlo methods were used to estimate the PDT power and type I error rate, and to compare them to those of the Single-Case Randomization Test (SCRT) assuming a randomly determined intervention point and the traditional permutation test assuming full exchangeability. Data were simulated without linear trends for five treatment effect levels (- 2, - 1, 0, 1, 2), five autocorrelation levels (0, .15, .30, .45, .60), and four observation number levels (30, 60, 90, 120). The power was calculated multiple times for all combinations of factor levels each generating 1000 replications. With 30 observations, the PDT showed sufficient power (≥ 80%) to detect medium treatment effects up to autocorrelation ≤ .45. Using 60 observations, the PDT showed sufficient power to detect medium treatment effects regardless of autocorrelation. With ≥ 90 observations, the PDT could also detect small treatment effects up to autocorrelation ≤ .30. With 30 observations, the type I error rate was 5-7%. With 60 observations and more, the type I error rate was ≤ 5% with autocorrelation < .60. The PDT outperformed the SCRT regarding power, particularly with a small number of observations. The PDT outperformed the traditional permutation test regarding type I error rate control, especially when autocorrelation increased. In conclusion, the PDT is a useful and promising nonparametric test to evaluate treatment effects in dependent SCOD AB-phase data without linear trends.

Internet-delivered cognitive behavioural therapy for chronic fatigue among adolescents with a chronic medical condition: a single case study.

BACKGROUND: Severe fatigue is a prominent symptom among adolescents with a chronic medical condition, with major impact on their well-being and daily functioning. Internet-based cognitive behavioural therapy (I-CBT) is a promising treatment for severe fatigue among adolescents with a chronic medical condition, but its effectiveness has not been studied. AIMS: We developed an I-CBT intervention for disabling fatigue in a chronic medical condition and tested its feasibility and effectiveness in an adolescent with an immune dysregulation disorder (IDD), namely juvenile idiopathic arthritis (JIA). METHOD: The application of I-CBT is illustrated through a clinical case study of a 15-year-old girl with JIA and chronic severe fatigue. An A-B single case experimental design was used with randomization of the waiting period prior to start of the intervention. Outcomes were weekly measures of fatigue severity, physical functioning, school absence and pain severity. RESULTS: Fatigue severity significantly decreased following I-CBT. Improvements were observed towards increased school attendance and improved physical functioning following the intervention, but these effects were too small to become significant. CONCLUSIONS: The study provides preliminary support for the feasibility and effectiveness of the application of I-CBT for severe fatigue in adolescents with a long-term medical condition.

Dynamic modeling of experience sampling methodology data reveals large heterogeneity in biopsychosocial factors associated with persistent fatigue in young people living with a chronic condition.

OBJECTIVE: To evaluate associations between self-reported biopsychosocial factors and persistent fatigue with dynamic single-case networks. METHODS: 31 persistently fatigued adolescents and young adults with various chronic conditions (aged 12 to 29 years) completed 28 days of Experience Sampling Methodology (ESM) with five prompts per day. ESM surveys consisted of eight generic and up to seven personalized biopsychosocial factors. Residual Dynamic Structural Equation Modeling (RDSEM) was used to analyze the data and derive dynamic single-case networks, controlling for circadian cycle effects, weekend effects, and low-frequency trends. Networks included contemporaneous and cross-lagged associations between biopsychosocial factors and fatigue. Network associations were selected for evaluation if both significant (α < 0.025) and relevant (ß ≥ 0.20). RESULTS: Participants chose 42 different biopsychosocial factors as personalized ESM items. In total, 154 fatigue associations with biopsychosocial factors were found. Most associations were contemporaneous (67.5%). Between chronic condition groups, no significant differences were observed in the associations. There were large inter-individual differences in which biopsychosocial factors were associated with fatigue. Contemporaneous and cross-lagged associations with fatigue varied widely in direction and strength. CONCLUSIONS: The heterogeneity found in biopsychosocial factors associated with fatigue underlines that persistent fatigue stems from a complex interplay between biopsychosocial factors. The present findings support the need for personalized treatment of persistent fatigue. Discussing the dynamic networks with the participant can be a promising step towards tailored treatment. TRIAL REGISTRATION: No. NL8789 (http://www.trialregister.nl).

Identifying disrupted biological factors and patient-tailored interventions for chronic fatigue in adolescents and young adults with Q-Fever Fatigue Syndrome, Chronic Fatigue Syndrome and Juvenile Idiopathic Arthritis (QFS-study): study protocol for a randomized controlled trial with single-subject experimental case series design.

BACKGROUND: Chronic fatigue with a debilitating effect on daily life is a frequently reported symptom among adolescents and young adults with a history of Q-fever infection (QFS). Persisting fatigue after infection may have a biological origin with psychological and social factors contributing to the disease phenotype. This is consistent with the biopsychosocial framework, which considers fatigue to be the result of a complex interaction between biological, psychological, and social factors. In line, similar manifestations of chronic fatigue are observed in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) and juvenile idiopathic arthritis (JIA). Cognitive behavioral therapy is often recommended as treatment for chronic fatigue, considering its effectiveness on the group level. However, not everybody benefits on the individual level. More treatment success at the individual level might be achieved with patient-tailored treatments that incorporate the biopsychosocial framework. METHODS: In addition to biological assessments of blood, stool, saliva, and hair, the QFS-study consists of a randomized controlled trial (RCT) in which a single-subject experimental case series (N=1) design will be implemented using Experience Sampling Methodology in fatigued adolescents and young adults with QFS, CFS/ME, and JIA (aged 12-29). With the RCT design, the effectiveness of patient-tailored PROfeel lifestyle advices will be compared against generic dietary advices in reducing fatigue severity at the group level. Pre-post analyses will be conducted to determine relevance of intervention order. By means of the N=1 design, effectiveness of both advices will be measured at the individual level. DISCUSSION: The QFS-study is a comprehensive study exploring disrupted biological factors and patient-tailored lifestyle advices as intervention in adolescent and young adults with QFS and similar manifestations of chronic fatigue. Practical or operational issues are expected during the study, but can be overcome through innovative study design, statistical approaches, and recruitment strategies. Ultimately, the study aims to contribute to biological research and (personalized) treatment in QFS and similar manifestations of chronic fatigue. TRIAL REGISTRATION: Trial NL8789 . Registered July 21, 2020.

Changed dynamic symptom networks after a self-compassion training in patients with somatic symptom disorder: A multiple single-case pilot project.

OBJECTIVE: Pre-to-post mean group differences of intermittently assessed generic outcome variables may not capture all relevant treatment-related changes in individual patients with somatic symptom disorder (SSD). Aim of this multiple single-case observational pilot project was to find out whether the Experience Sampling Method (ESM) and dynamic symptom networks may offer new opportunities in evaluating treatment outcomes for individual patients with SSD. METHODS: Patients with SSD (N = 6 in study 1, N = 7 in study 2) received a self-compassion training in a tertiary care mental health expert center. Using a single-case pre-post treatment observational design, intensive longitudinal data were collected with ESM. A brief questionnaire was presented via the patient's smartphone three times per day for 16 weeks before, during and after the training in study 1, and for 5 weeks before and 5 weeks after the training in study 2. Eleven questions comprised somatic symptoms, functional disability, stress, self-compassion, and acceptance of affect; three personalized questions comprised self-chosen affects and an additional symptom. RESULTS: Sufficient observations for means and network comparison were obtained for 11 and 10 patients, respectively. After the training, self-compassion was significantly increased in 10 patients, functional disability, stress and affect improved in 6 patients, and (although not a treatment goal) somatic symptoms decreased in 6 patients. Dynamic symptom networks significantly changed in 5 patients. CONCLUSION: Patient-specific changes in means and dynamic symptom networks were observed after self-compassion training. In future clinical trials, single-case ESM may offer new opportunities to evaluate treatment outcomes in patients with SSD.

Internet and smartphone-based ecological momentary assessment and personalized advice (PROfeel) in adolescents with chronic conditions: A feasibility study.

OBJECTIVE: Growing up with a chronic disease comes with challenges, such as coping with fatigue. Many adolescents are severely fatigued, though its associated factors exhibit considerable interpersonal and longitudinal variation. We assessed whether PROfeel, a combination of a smartphone-based ecological momentary assessment (EMA) method using the internet, followed by a face-to-face dialogue and personalized advice for improvement of symptoms or tailor treatment based on a dynamic network analysis report, was feasible and useful. STUDY DESIGN: Feasibility study in fatigued outpatient adolescents 12-18 years of age with cystic fibrosis, autoimmune disease, post-cancer treatment, or with medically unexplained fatigue. Participants were assessed at baseline to personalize EMA questions. EMA was conducted via smartphone notifications five times per day for approximately six weeks. Hereby, data was collected via the internet. The EMA results were translated into a personalized report, discussed with the participant, and subsequently translated into a personalized advice. Afterwards, semi-structured interviews on feasibility and usefulness were held. RESULTS: Fifty-seven adolescents were assessed (mean age 16.2 y ± 1.6, 16% male). Adolescents deemed the smartphone-based EMA feasible, with the app being used for an average of 49 days. Forty-two percent of the notifications were answered and 85% of the participants would recommend the app to other adolescents. The personalized report was deemed useful and comprehensible and 95% recognized themselves in the personalized report, with 64% rating improved insight in their symptoms and subsequent steps towards an approach to reduce one's fatigue as good or very good. CONCLUSIONS: PROfeel was found to be highly feasible and useful for fatigued adolescents with a chronic condition. This innovative method has clinical relevance through bringing a patient's daily life into the clinical conversation.

Ecological momentary assessment study of exposure to radiofrequency electromagnetic fields and non-specific physical symptoms with self-declared electrosensitives.

The main objective of the study is to determine if non-specific physical symptoms (NSPS) in people with self-declared sensitivity to radiofrequency electromagnetic fields (RF EMF) can be explained (across subjects) by exposure to RF EMF. Furthermore, we pioneered whether analysis at the individual level or at the group level may lead to different conclusions. By our knowledge, this is the first longitudinal study exploring the data at the individual level. A group of 57 participants was equipped with a measurement set for five consecutive days. The measurement set consisted of a body worn exposimeter measuring the radiofrequency electromagnetic field in twelve frequency bands used for communication, a GPS logger, and an electronic diary giving cues at random intervals within a two to three hour interval. At every cue, a questionnaire on the most important health complaint and nine NSPS had to be filled out. We analysed the (time-lagged) associations between RF-EMF exposure in the included frequency bands and the total number of NSPS and self-rated severity of the most important health complaint. The manifestation of NSPS was studied during two different time lags - 0-1 h, and 1-4 h - after exposure and for different exposure metrics of RF EMF. The exposure was characterised by exposure metrics describing the central tendency and the intermittency of the signal, i.e. the time-weighted average exposure, the time above an exposure level or the rate of change metric. At group level, there was no statistically significant and relevant (fixed effect) association between the measured personal exposure to RF EMF and NSPS. At individual level, after correction for multiple testing and confounding, we found significant within-person associations between WiFi (the self-declared most important source) exposure metrics and the total NSPS score and severity of the most important complaint in one participant. However, it cannot be ruled out that this association is explained by residual confounding due to imperfect control for location or activities. Therefore, the outcomes have to be regarded very prudently. The significant associations were found for the short and the long time lag, but not always concurrently, so both provide complementary information. We also conclude that analyses at the individual level can lead to different findings when compared to an analysis at group level.

A concept mapping study on perpetuating factors of functional somatic symptoms from clinicians' perspective.

OBJECTIVE: The aim of this concept mapping study was to identify the structure and alleged importance of perpetuating factors of functional somatic symptoms (FSS) from the perspective of professionals. Further, we examined to which extent these factors have been addressed in scientific literature. METHODS: Ninety-nine perpetuating factors were sorted with respect to content using a card-sorting task by 61 experienced clinicians (62.3% psychologists, 75.4% female, mean age: 45.7 [SD: 10.6] years, mean duration of experience in treating FSS patients: 10.5 [SD: 7.6] years). These factors had been derived from in-depth interviews with 12 clinicians, with extensive experience in treating FSS. Thirty-eight clinicians rated the importance of the 99 factors on a scale ranging from 1 ('not important at all') to 10 ('extremely important'). RESULTS: Hierarchical cluster analysis revealed three overarching domains of perpetuating factors: 'Hypochondria', 'Social and relational problems' and 'Symptom-related emotions and habits'. These domains comprised 16 clusters, which were rated on importance between 6.1, 'Adverse physical factors and counterproductive lifestyle', and 7.8, 'Frustration and despair regarding the symptoms'. All clusters have been addressed in scientific literature. CONCLUSIONS: This study revealed an encompassing hierarchical structure of somatic, emotional, cognitive, behavioral, and social factors of importance in the perpetuation of FSS based on expert opinions. This structure will guide the development of personalized treatment of FSS.

Incorporating measurement error in n = 1 psychological autoregressive modeling.

Measurement error is omnipresent in psychological data. However, the vast majority of applications of autoregressive time series analyses in psychology do not take measurement error into account. Disregarding measurement error when it is present in the data results in a bias of the autoregressive parameters. We discuss two models that take measurement error into account: An autoregressive model with a white noise term (AR+WN), and an autoregressive moving average (ARMA) model. In a simulation study we compare the parameter recovery performance of these models, and compare this performance for both a Bayesian and frequentist approach. We find that overall, the AR+WN model performs better. Furthermore, we find that for realistic (i.e., small) sample sizes, psychological research would benefit from a Bayesian approach in fitting these models. Finally, we illustrate the effect of disregarding measurement error in an AR(1) model by means of an empirical application on mood data in women. We find that, depending on the person, approximately 30-50% of the total variance was due to measurement error, and that disregarding this measurement error results in a substantial underestimation of the autoregressive parameters.

The day-to-day concurrence of bodily complaints and affect in patients with severe somatoform disorder.

Based on the concept of somatization, psychological distress can be experienced as symptoms of physical illness. This suggests a close-fitting intra-individual association between bodily complaints and mood in patients with somatoform disorder (SFD). The contemporaneous day-to-day complaints-mood association was investigated in patients with severe chronic SFD using an ecological momentary assessment (EMA) design. Eleven patients, who had recently received specialized tertiary care treatment for severe chronic SFD, kept an online electronic diary for four consecutive weeks. They were prompted at intervals throughout the day to complete questions on their momentary primary symptoms (pain and fatigue), and mood state (negative and positive). For each measure, day-mean aggregated values were computed and analyzed using linear multilevel (mixed model) regression analysis. Fixed factor results showed that symptoms were associated with both negative mood state (ß = 0.47) and positive mood state (ß = -0.59). Random results, however, indicated large inter-individual differences, with correlations varying between 0.17 and 0.99 for negative affect, and between -0.88 and 0.14 for positive affect. A substantial day-to-day contemporaneous association between symptoms and affect across subjects, as well as large inter-individual differences in this association, were demonstrated in patients with severe chronic SFD. EMA-data showing the relationship between both negative and (inverse) positive mood and complaints has potential clinical relevance: providing SFD patients with feedback consisting of their personal day-to-day concurrency graph may promote their understanding of their own complaints in a broader context than the somatic area.

Intensive multidisciplinary treatment of severe somatoform disorder: a prospective evaluation.

Chronic severe somatoform disorder (SFD) is resistant to treatment. In a prospective observational study, we evaluated an intensive multidisciplinary treatment focusing on body-related mentalization and acceptance. Patients included in the study were 183 (146 women, 37 men) of 311 eligible patients with chronic severe SFD, referred consecutively to a specialized tertiary care center between 2002 and 2009. Primary outcome measures were somatic symptoms (SCL-90) and health-related quality of life (EuroQol 5-Dimensional [EQ-5D]). These measures were assessed four times before treatment (on intake, twice during an observation period, at start of treatment) and four times after treatment (during follow-up for 2 years). Multilevel analysis was used to separate effects of time (maturation) and treatment. Results revealed significant improvements in SCL-90 somatic symptoms (d = 0.51), EQ-5D index (d = 0.27), and EQ visual analogue scale (d = 0.56). Significant reductions were also observed in SCL-90 anxiety, depression, and overall psychopathology as well as in medical consumption associated with psychiatric illness (Trimbos/iMTA Questionnaire for Costs Associated With Psychiatric Illness). Large interindividual differences were found in treatment outcome. The long-term improvement seen in many patients suggests that intensive multidisciplinary tertiary care treatment is a useful approach to chronic severe SFD.

Effectiveness of psychotherapy for severe somatoform disorder: meta-analysis.

BACKGROUND: Patients with severe somatoform disorder (in secondary and tertiary care) typically experience functional impairment associated with physical symptoms and mental distress. Although psychotherapy is the preferred treatment, its effectiveness remains to be demonstrated. AIMS: To examine the effectiveness of psychotherapy for severe somatoform disorder in secondary and tertiary care compared with treatment as usual (TAU) but not waiting-list conditions. METHOD: Main inclusion criteria were presence of a somatoform disorder according to established diagnostic criteria and receiving psychotherapy for somatoform disorder in secondary and tertiary care. Both randomised and non-randomised trials were included. The evaluated outcome domains were physical symptoms, psychological symptoms (depression, anxiety, anger, general symptoms) and functional impairment (health, life satisfaction, interpersonal problems, maladaptive cognitions and behaviour). RESULTS: Ten randomised and six non-randomised trials were included, comprising 890 patients receiving psychotherapy and 548 patients receiving TAU. Psychotherapy was more effective than TAU for physical symptoms (d = 0.80 v. d = 0.31, P<0.05) and functional impairment (d = 0.45 v. d = 0.15, P<0.01), but not for psychological symptoms (d = 0.75 v. d = 0.51, P = 0.21). These effects were maintained at follow-up. CONCLUSIONS: Overall findings suggest that psychotherapy is effective in severe somatoform disorder. Future randomised controlled studies should examine specific interventions and mechanisms of change.

Infection load as a predisposing factor for somatoform disorders: evidence from a Dutch General Practice Registry.

OBJECTIVE: Somatoform disorders (SDs) are characterized by chronic multiple functional somatic (FS) symptoms. It has been suggested that infections may be triggers for FS symptoms to occur, pointing to the immune system as a pathogenic factor in their development. The current study aimed to compare the prevalence of infections (i.e., infection load) in the history of patients with SDs with that of matched controls. METHODS: Samples (n = 185) were identified in the Psychiatric Case Register Middle Netherlands and the Julius General Practitioners Network. Patients with an SD diagnosis in the Psychiatric Case Register Middle Netherlands were compared with matched persons without somatoform complaints (controls) on their infection load in two periods before the date of the psychiatric diagnosis or a matched date for the controls (i.e., the total period for which data were available and a 3-year period). Infection load was defined as the total number of infections documented in the Julius General Practitioners Network. RESULTS: Patients with SD had significantly more infections than did controls in both periods (total period: mean [standard error] = 0.87 [0.10] versus 0.51 [0.06], z = -3.08, p = .002; 3-year period: 3.44 [0.47] versus 2.15 [0.50], z = -2.91, p = .004). CONCLUSIONS: Results show that patients with SD have a higher infection load preceding their diagnosis as compared with matched controls, implicating that infection load may indeed predispose for developing FS symptoms. These findings emphasize the importance of further research on immunological mechanisms in FS symptoms. Limitations of the study are discussed.

Prodromal functioning of migraine patients relative to their interictal state--an ecological momentary assessment study.

Smartphones were used in an online Ecological Momentary Assessment (EMA) design to test prodromal functioning relative to the interictal state in migraine patients. Eighty-seven participants completed an electronic diary 4 times daily during 3-6 weeks to monitor their migraine attacks. Twice daily the diary additionally included 16 multi-answer questions covering physical symptoms (30 items), cognitive-affective functioning (25 items) and external factors (25 items). Eight clustered prodromal features were identified in the current study: sensory sensitivity, pain/stiffness, fatigue, cognitive functioning, positive affect, negative affect, effort spent and stressors encountered. Per feature, individual change scores with interictal control days--excluding 24-hour post-attack recovery--were computed for six 12-hour pre-attack time windows covering three prodromal days. Linear mixed model (fixed-effect) analysis established significant increases in sensory sensitivity, pain/stiffness and fatigue, and a tendency for increased negative affect, in the 12 hours prior to the attack. Positive affect and cognitive functioning were impaired both in the 25-36 hour and--more strongly--in the 12-hour time window before the attack. No effects were found for effort spent and stressors encountered. Exploratory (random effect) analysis revealed significant individual differences in the change scores in sensory sensitivity, pain/stiffness, fatigue and negative affect. It is concluded that the prodromal change in migraine--relative to interictal functioning--predominantly exists within the last 12 hours before attack onset. Individual diversity is large, however. Future research should zoom in to identify prodrome development within the 12 pre-attack hours as well as to isolate individual patterns.

The impact of emotion-related autonomic nervous system responsiveness on pain sensitivity in female patients with fibromyalgia.

OBJECTIVE: Patients with fibromyalgia have shown hyporeactive autonomic nervous system (ANS) responses to physical stressors, augmented pain to ANS changes, and heightened negative emotions, which can increase pain. This study examined ANS reactivity to negative emotions and its association with pain in fibromyalgia and control participants. METHODS: Sixty-two women with fibromyalgia and 59 women in a control group recalled neutral, and anger- and sadness-eliciting experiences while ANS activity was monitored. Clinical and experimental pain were assessed in response to each emotion. RESULTS: Compared with neutral recall, heart rate (p = .050), mean arterial pressure (p < .001), and high-frequency heart rate variability (p = .012) increased in response to sadness, whereas heart rate decreased (p = .002) and mean arterial pressure increased (p < .001) in response to anger; however, ANS responses did not differ between patients and control participants (all p > .29). Among patients only, decreased preejection period (anger-pain threshold: r = 0.31, p = .018) and total peripheral resistance in response to negative emotions (anger-pain tolerance: r = 0.35, p = .025; sadness-pain threshold: r = 0.51, p < .001; sadness-pain tolerance: r = 0.61, p < .001) correlated with more pain. CONCLUSIONS: These data suggest that the ANS is not hyporesponsive to elicited emotions in fibromyalgia; however, patients with a larger pain response showed an ANS response pattern reflecting heightened ß-adrenergic and reduced α-adrenergic reactivity. Future research should test whether a specific ANS response pattern to emotions is a consequence of increased pain or whether it amplifies pain.

Design of an ecological momentary assessment study of exposure to radiofrequency electromagnetic fields and non-specific physical symptoms.

INTRODUCTION: Idiopathic Environmental Intolerance (IEI) attributed to electromagnetic fields (EMF) refers to self-reported sensitivity mainly characterised by the attribution of non-specific physical symptoms to low-level EMF exposure emitted from sources such as mobile phones. Scientific studies have not provided evidence for the existence of IEI-EMF, but these studies did not resemble the real-life situation or suffered from poor exposure characterisation and biased recall of health symptoms. To improve existing methods for the study of IEI-EMF, an Ecological Momentary Assessment (EMA) study is designed. METHODS AND ANALYSIS: The study is an EMA study in which respondents carry personal exposure metres (exposimeters) that measure radiofrequency (RF) EMF, with frequent assessment of health symptoms and perceived EMF exposure through electronic diary registration during five consecutive days. Participants will be a selection from an epidemiological study who report to be sensitive to RF EMF. The exposimeters measure electric field strength in 12 frequency bands. Diary questions include the occurrence and severity of 10 non-specific physical symptoms, mood states and perceived exposure to (sources of) EMF. The relationship of actual and perceived EMF exposure and mood with non-specific physical symptoms will be analysed using multilevel regression analysis with time-shift models. DISCUSSION: The study has several advantages over previous studies, including assessment of personal EMF exposure and non-specific physical symptoms by an ecological method with a minimised chance of recall bias. The within-person design reduces confounding by time-stable factors (eg, personal characteristics). In the conduct of the study and the analysis and interpretation of its outcomes, some methodological issues including a high participant burden, reactivity, compliance to the study protocol and the potential of chance findings due to multiple statistical testing will be accounted for and limited as much as possible.