Cognitive dysfunction in fibromyalgia and chronic fatigue syndrome: New trends and future directions

Impact of Repetitive Transcranial Magnetic Stimulation on Cognitive and Psychiatric Dysfunction in Patients with Fibromyalgia: A Double-Blinded, Randomized Clinical Trial

Few randomized controlled trials have reported that repetitive transcranial magnetic stimulation (rTMS) has controversial results for managing multiple domains of fibromyalgia-related symptoms. This work aimed to evaluate the effect of low-frequency rTMS over the right dorsolateral prefrontal area (DLPFC) on the Fibromyalgia Impact Questionnaire (FIQ) concerning psychiatric and cognitive disorders. Forty-two eligible patients with fibromyalgia (FM) were randomized to have 20 sessions of active or sham rTMS (1 Hz, 120% of resting motor threshold with a total of 1200 pules/session) over the right DLPFC. All participants were evaluated at baseline, post sessions, and 3 months after sessions with the FIQ, Hamilton depression, and anxiety rating scales (HDRS and HARS), Montreal Cognitive Assessment (MoCA), Rey Auditory Verbal Learning Test (RAVLT), Tower of London test (TOL), the Trail Making, and Digit Span Tests. Both groups showed improvement in most rating scales at 1 and 3 months follow-up, with greater improvement in the active group, with significant correlation between FIQ cognitive rating scales, including RAVLT and TOL. Twenty sessions of low-frequency rTMS over the right DLPFC can improve FIQ scores regarding the psychiatric and cognitive symptoms of medicated patients with FM to a greater extent than sham. Changes in RAVLT and TOL correlated with changes in FIQ results.

Preferences for risks and benefits of treatment outcomes for chronic low back pain: Choice-based conjoint measure development and discrete choice experiment

INTRODUCTION

Understanding individual patient preferences for chronic low back pain (cLBP) outcomes is essential for targeting available therapeutic options; yet tools to elicit patient outcome preferences are limited.

OBJECTIVE

To develop and test a choice-based conjoint (CBC) measure, commonly used in behavioral economics research, to elicit what outcomes patients with cLBP want to achieve and avoid.

DESIGN

We developed a survey-based CBC measure to allow patients to make risk/benefit trade-off choices between possible treatment outcomes. After extensive literature, clinician, and patient input, our measure included seven attributes: fatigue, anxiety/depression, difficulty thinking/making decisions, pain intensity, physical abilities, change in pain, and ability to enjoy life despite pain. Random-parameters logit models were used to estimate strength of preferences, and latent class analysis was used to identify patient characteristics associated with distinct preference.

SETTING

Online study using the Sawtooth web-based platform.

PARTICIPANTS

Two hundred eleven individuals with cLBP recruited from online advertising as well as at clinical sites across multiple academic and private institutions.

INTERVENTIONS

Not applicable.

RESULTS

The most valued outcome was the highest level of physical activity (β = 1.6-1.98; p < .001), followed by avoiding cognitive difficulties (β = -1.48; p < .001). Avoidance of severe pain was comparable to avoiding constant fatigue and near-constant depression/anxiety (β = -0.99, -1.02); p < .001). There was an association between preferences and current pain/disability status; patients with higher pain had a stronger preference to avoid severe pain, whereas those with higher disability have stronger preferences for achieving physical activity. The latent class analysis identified two distinct groups: (1) more risk-seeking and willing to accept worse outcomes (56%); and (2) more risk-averse with a stronger preference for achieving maximum benefits (44%).

CONCLUSIONS

Our study illuminated cLBP patient preferences for treatment outcomes and heterogeneity in these preferences. Patients stressed the importance of reaching high physical activity and avoiding cognitive declines, even over a desire to avoid pain. More work is needed to understand patient preferences to aid informed, shared decisions.

Fibromyalgia Syndrome and Cognitive Decline: The Role of Body Mass Index and Clinical Symptoms

The high prevalence of obesity and overweight in fibromyalgia (FM) may be an important factor in the well-known cognitive deficits seen in the disorder. This study analyzed the influence of body mass index (BMI) and primary clinical symptoms of FM (pain, fatigue, insomnia, anxiety, and depression) on attention, memory, and processing speed in FM. Fifty-two FM patients and thirty-two healthy participants completed cognitive tasks assessing selective, sustained, and divided attention; visuospatial and verbal memory; and information processing speed. Furthermore, they were evaluated in terms of the main clinical symptoms of the disorder. FM patients showed a marked reduction of cognitive performance in terms of selective, sustained, and divided attention; visuospatial memory; and processing speed, but no group differences were observed in verbal memory. BMI negatively affects sustained and selective attention, verbal memory, and processing speed and is the main predictor of performance in these basic cognitive domains. Our findings confirm the presence of cognitive deficits with respect to attention and visual memory, as well as slower processing speed, in FM. Moreover, the results support a role of BMI in the observed cognitive deficits. Interventions increasing physical activity and promoting cognitive stimulation could be useful for strengthening cognitive function in FM patients.

Altered sub-processes of working memory in fibromyalgia patients: An ERP study using N-back task

OBJECTIVE

Cognitive dysfunction in fibromyalgia has become a key symptom considered by patients as more disabling than pain itself. Experimental evidence from neuropsychological and neuroimaging studies indicates that such cognitive impairments are especially robust when patients need to set in motion working memory processes, suggesting the existence of an altered functioning underlying the cerebral cortices of the frontoparietal memory network. However, the temporal dynamics of working memory sub-processes have not yet been explored in fibromyalgia.

SUBJECTS

Thirty-six right-handed women participated in the experiment: comprising eighteen patients with fibromyalgia and eighteen healthy controls.

METHODS

Event-related potentials (ERPs) and behavioural responses were recorded while participants were engaged in a 2-back working memory task. Principal Component Analyses (PCA) were used to define and quantify the ERP components associated with working memory processes.

RESULTS

Fibromyalgia patients exhibited worse performance than the control group, as revealed by their number of errors in the working memory task. Moreover, both scalp parieto-occipital P2 and parieto-occipital P3 amplitudes were lower for patients than for healthy control participants. Regression analyses revealed that lower P3 amplitudes were observed in those patients with fibromyalgia reporting higher pain ratings.

CONCLUSIONS

Current results suggest that both encoding of information (as reflected by P2) and subsequently, context updating and the replacement (as seen in lower P3 amplitudes), as a part of working memory sub-processes, are impaired in fibromyalgia. Studying the temporal dynamics of working memory using ERP methodology is a helpful approach to detect specific cognitive impaired mechanisms in this chronic pain syndrome. These new data could be used to develop more specific treatments adapted for each patient.

Memory complaints and cognitive performance in fibromyalgia and chronic pain: The key role of depression

To explore the relationship between perceived cognitive problems and cognitive performance in three different samples, taking into account the possible influence of depression, catastrophizing, pain intensity, or medication. Seventy individuals with fibromyalgia, 74 with non-malignant chronic pain and 40 pain-free controls, completed measures of verbal episodic memory, sustained attention, response inhibition, depression, catastrophizing, and pain intensity. Fibromyalgia and chronic pain patients performed worse than controls in verbal memory and sustained attention, but these differences disappeared when depressed participants were excluded from the analyses. Memory complaints were related with depression in all pain patients. However, in the case of fibromyalgia, memory complaints were also related by pain intensity and inversely related by short-term episodic memory. This case-control study shows the importance of jointly assessing cognitive performance and memory complaints and of controlling for variables such as depression, catastrophizing, pain intensity and medication in the studied samples. Accordingly, this study highlights the differences in memory complaints, between the patients with fibromyalgia and the patients with other chronic pain conditions. Finally, it has highlighted the important role played by depression in cognitive performance and memory complaints considering the Neurocognitive Model of Attention to pain.

Screening for Adult ADHD in Patients with Fibromyalgia Syndrome

Objective

Fibromyalgia syndrome (FMS) is a common chronic pain disorder associated with altered activity of neurotransmitters involved in pain sensitivity such as dopamine, serotonin, and noradrenaline. FMS may significantly impact an individual's functioning due to the presence of chronic pain, fatigue, and cognitive impairment. Dyscognition may be more disabling than the chronic pain but is mostly under-recognized. This study aimed to assess the potential co-occurrence of FMS and adult attention deficit hyperactivity disorder (ADHD), a chronic neurodevelopmental disorder also associated with impaired cognition and dopaminergic function.

Methods

In a cross-sectional observational study, 123 previously confirmed FMS patients were screened for adult ADHD using the World Health Organization Adult ADHD Self Report scale v1.1. The Revised Fibromyalgia Impact Questionnaire (FIQ-R) was used to assess the impact of FMS. Cognitive assessment was based on self-report in accordance with the 2011 modified American College of Rheumatology criteria and the FIQ-R, respectively.

Results

Of the 123 participants, 44.72% (N = 55) screened positive for adult ADHD. Participants with both FMS and a positive adult ADHD screening test scored higher on the FIQ-R score (64.74, SD = 17.66, vs 54.10, SD = 17.10). Self-reported cognitive impairment was rated higher in the combined group (odds ratio = 10.61, 95% confidence interval; 3.77-29.86, P < 0.01).

Conclusions

These results indicate that the co-occurrence of adult ADHD in FMS may be highly prevalent and may also significantly impact the morbidity of FMS. Patients with FMS should be assessed for the presence of adult ADHD.

Multidimensional Comparison of Cancer-Related Fatigue and Chronic Fatigue Syndrome: The Role of Psychophysiological Markers

OBJECTIVE

The present study compared cancer-related fatigue (CRF) and chronic fatigue syndrome (CFS) using multidimensional measurements with the aim of better understanding characteristics and exploring markers of two similar fatigue syndromes.

METHODS

Twenty-five patients with CRF and twenty patients with CFS completed questionnaires, including the Fatigue Severity Scale (FSS), Hospital Anxiety Depression Scale (HADS), Perceived Stress Scale (PSS), and Pittsburgh Sleep Quality Index (PSQI). Additionally, levels of high sensitivity C-reactive protein (hs-CRP), heart rate variability (HRV), and electroencephalography (EEG) were obtained. Neurocognitive functioning was also evaluated.

RESULTS

Both groups showed comparable levels of psychological variables, including fatigue. Compared to CFS subjects, CRF patients had significantly higher hs-CRP levels and a reduced HRV-index. The within-group analyses revealed that the FSS score of the CRF group was significantly related to scores on the HADS-anxiety, HADS-depression, and PSQI scales. In the CFS group, FSS scores were significantly associated with scores on the PSS and the absolute delta, theta, and alpha powers in frontal EEG.

CONCLUSION

Findings indicate that different pathophysiological mechanisms underlie CFS and CRF. Inflammatory marker and HRV may be potential biomarkers for distinguishing two fatigue syndromes and frontal EEG parameters may be quantitative biomarkers for CFS.

A Concurrent Cognitive Task Does Not Perturb Quiet Standing in Fibromyalgia and Chronic Fatigue Syndrome

Background and Objectives

Cognitive complaints are common in fibromyalgia (FM) and chronic fatigue syndrome (CFS). Fatigue as well as pain may require greater effort to perform cognitive tasks, thereby increasing the load on processing in the central nervous system and interfering with motor control.

Methods

The effect of a concurrent arithmetic cognitive task on postural control during quiet standing was investigated in 75 women (aged 19–49 years) and compared between FM, CFS, and matched controls (n=25/group). Quiet standing on a force plate was performed for 60 s/condition, with and without a concurrent cognitive task. The center of pressure data was decomposed into a slow component and a fast component representing postural sway and adjusting ankle torque.

Results

Compared to controls, CFS and FM displayed lower frequency in the slow component (p < 0.001), and CFS displayed greater amplitude in the slow (p=0.038 and p=0.018) and fast (p=0.045) components. There were no interactions indicating different responses to the added cognitive task between any of the three groups.

Conclusion

Patients displayed insufficient postural control across both conditions, while the concurrent cognitive task did not perturb quiet standing. Fatigue but not pain correlated with postural control variables.

A Pilot Randomized Controlled Trial to Explore Cognitive and Emotional Effects of Probiotics in Fibromyalgia

It has recently been found that microbes in the gut may regulate brain processes through the gut microbiota–brain axis, which modulates affection, motivation and higher cognitive functions. According to this finding, the use of probiotics may be a potential treatment to improve physical, psychological and cognitive status in clinical populations with altered microbiota balance such as those with fibromyalgia (FMS). Thus, the aim of the present pilot study with a double-blind, placebo-controlled, randomised design was to test whether a multispecies probiotic may improve cognition, emotional symptoms and functional state in a sample of patients diagnosed with FMS. Pain, impact of FMS, quality of life, anxiety and depressive symptoms were measured during the pre- and post-intervention phases; participants also completed two computerised cognitive tasks to assess impulsive choice and decision-making. Finally, urinary cortisol concentration was determined. To our knowledge, this is the first study that explore the effect of a multispecies probiotic in FMS patients. Our results indicated that probiotics improved impulsivity and decision-making in these patients. However, more research is needed to further explore the potential effects of probiotics on other cognitive functions affected in FMS as well as in other clinical populations.

Cognitive Impairment in Fibromyalgia: A Meta-Analysis of Case-Control Studies

OBJECTIVE

Cognitive dysfunction has been reported in individuals with fibromyalgia. However, findings regarding cognitive function examined using neuropsychological tests have been inconsistent. The aim of the study was to determine domain-specific cognitive impairment in patients with fibromyalgia compared with healthy controls.

METHODS

We conducted a meta-analysis that systematically searched six databases (PubMed, Ovid MEDLINE, Embase, CINAHL, PsycINFO, and Web of Science) for articles published before September 2017.

RESULTS

Twenty-three case-control studies with a total of 2096 participants were included in the meta-analysis. Cognitive function was significantly lower (g = 0.87, 95% confidence interval [CI] = 0.60-1.15) in individuals with fibromyalgia than in healthy controls. Large effect sizes were found in learning/memory and attention/psychomotor speed (g = 0.94, p = .013; g = 1.22, p < .001, respectively); medium effect sizes were reported in executive function and working memory (g = 0.72, p < .001; g = 0.75, p < .001, respectively). Depression and anxiety scores were associated with the effect size of group differences in cognitive function (B = 0.11, p < .001, 95% CI = 0.09-0.13; B = 0.02, p < .001, 95% CI = 0.01-0.02, respectively).

CONCLUSIONS

Cognitive impairment across different cognitive domains was found in individuals with fibromyalgia compared with healthy controls. Mood states (depression and anxiety) may explain the heterogeneity across studies.

Determining the Minimal Clinically Important Difference for 6-Minute Walk Distance in Fibromyalgia

OBJECTIVE

The aim of this study was to estimate the minimal clinically important difference (MCID) for 6-min walk distance (6MWD) in patients with fibromyalgia.

DESIGN

Data from a recently completed trial that included 187 patients who completed the 6-min walk test, Fibromyalgia Impact Questionnaire (FIQ), and Short-Form 36 (SF36) at 12 and 36 wks were used to examine longitudinal changes in 6MWD. An anchor-based approach that used linear regression analyses was used to determine the MCID for 6MWD, using the total FIQ score (FIQ-Total) and SF36-physical function domain as clinical anchors.

RESULTS

The mean (SD) change in 6MWD from baseline to week 36 was 34.4 (65.2) m (P < 0.001). The anchor-based MCIDs for the 6MWD were 156 and 167 m for the FIQ and SF36-physical function domain, respectively. These MCIDs correspond with clinically meaningful improvements in FIQ (14% reduction) and SF36-physical function domain (10-point increase).

CONCLUSION

The MCID for 6MWD in patients with fibromyalgia was 156 to 167 m. These findings provide the first evidence of the change in 6MWD that is perceived by patients to be clinically meaningful. Further research using other MCID calculation methods is needed to refine estimates of the MCID for 6MWD in patients with fibromyalgia.

Anodal transcranial direct current stimulation over the left dorsolateral prefrontal cortex modulates attention and pain in fibromyalgia: randomized clinical trial

Cognitive dysfunction in fibromyalgia patients has been reported, especially when increased attentional demands are required. Transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) has been effective in modulating attention. We tested the effects of a single session of tDCS coupled with a Go/No-go task in modulating three distinct attentional networks: alertness, orienting and executive control. Secondarily, the effect on pain measures was evaluated. Forty females with fibromyalgia were randomized to receive active or sham tDCS. Anodal stimulation (1 mA, 20 min) was applied over the DLPFC. Attention indices were assessed using the Attention Network Test (ANT). Heat pain threshold (HPTh) and tolerance (HPTo) were measured. Active compared to sham tDCS led to increased performance in the orienting (mean difference [MD] = 14.63) and executive (MD = 21.00) attention networks. There was no effect on alertness. Active tDCS increased HPTh as compared to sham (MD = 1.93) and HPTo (MD = 1.52). Regression analysis showed the effect on executive attention is mostly independent of the effect on pain. DLPFC may be an important target for neurostimulation therapies in addition to the primary motor cortex for patients who do not respond adequately to neurostimulation therapies.

Gross and fine motor function in fibromyalgia and chronic fatigue syndrome

Purpose

This paper aimed to investigate motor proficiency in fine and gross motor function, with a focus on reaction time (RT) and movement skill, in patients with fibromyalgia (FM) and chronic fatigue syndrome (CFS) compared to healthy controls (HC).

Methods

A total of 60 individuals (20 CFS, 20 FM, and 20 HC), age 19–49 years, participated in this study. Gross motor function in the lower extremity was assessed using a RT task during gait initiation in response to an auditory trigger. Fine motor function in the upper extremity was measured during a precision task (the Purdue Pegboard test) where the number of pins inserted within 30 s was counted.

Results

No significant differences were found between FM and CFS in any parameters. FM and CFS groups had significantly longer RT than HC in the gait initiation (p=0.001, and p=0.004 respectively). In the Purdue Pegboard test, 20% in the FM group, 15% in the CFS groups, and 0% of HC group, scored below the threshold of the accepted performance. However, there were no significant differences between FM, CFS, and HC in this task (p=0.12).

Conclusion

Compared to controls, both CFS and FM groups displayed significantly longer RT in the gait initiation task. Generally, FM patients showed the worst results in both tests, although no group differences were found in fine motor control, according to the Purdue Pegboard test.

Usefulness of K-Point Injection for the Nonspecific Neck Pain in So-Called K-Point Syndrome

Background

Shoichi Kokubun introduced his successful experience with local anesthetic injection at the occipital insertion of the sternocleidomastoid muscle in K-point syndrome. The purpose of this study was to evaluate the short-term and long-term effectiveness of K-point injection and investigate factors affecting treatment results.

Methods

K-point injection was performed in 58 patients with K-point syndrome at Yeungnam University Medical Center. The syndrome was associated with cervical whiplash injury in 10 patients and was of nonspecific origin in the rest. One milliliter of 2% lidocaine mixed with 1 milliliter of dexamethasone was injected in 50 patients and 2 milliliters of 1% lidocaine alone in the rest. Initially, the severity of local tenderness at the K-point and other tender points was examined and the degree of immediate pain relief effect was assessed within 1 hour after injection. Early effect within 1 month after the injection and current effect were evaluated in 27 patients using a modified Kim's questionnaire with regard to the duration of improvement, degree of improvement in pain and daily living activities, and satisfaction.

Results

Of the total 58 patients, 44 (75.8%) apparently had immediate pain relief after K-point injection. The only factor associated with successful immediate pain relief was the whiplash injury associated with traffic accident (TA). The early pain control effect was associated with the immediate effect. The current effect was associated with the early effect alone. Satisfaction with the K-point injection was related to early successful pain relief.

Conclusions

K-point injection would be useful for early pain relief in nonspecific neck pain syndrome so called K-point syndrome, but not for current pain relief. Especially, it was very effective for early pain control in the whiplash injury associated with TA.

Is there a Lyme-like disease in Australia? Summary of the findings to date

Lyme Borreliosis is a common tick-borne disease of the northern hemisphere caused by the spirochaetes of the Borrelia burgdorferi sensu lato (B. burgdorferi s. l.) complex. It results in multi-organ disease with arthritic, cardiac, neurological and dermatological manifestations. In the last twenty-five years there have been over 500 reports of an Australian Lyme-like syndrome in the scientific literature. However, the diagnoses of Lyme Borreliosis made in these cases have been primarily by clinical presentation and laboratory results of tentative reliability and the true cause of these illnesses remains unknown. A number of animals have been introduced to Australia that may act as B. burgdorferi s. l. reservoirs in Lyme-endemic countries, and there are some Australian Ixodes spp. and Haemaphysalis spp. ticks whose geographical distribution matches that of the Australian Lyme-like cases. Four published studies have searched for Borrelia in Australian ticks, with contradicting results. The cause of the potential Lyme-like disease in Australia remains to be defined. The evidence to date as to whether these illnesses are caused by a Borrelia species, another tick borne pathogen or are due to a novel or unrelated aetiology is summarised in this review.

The Experience of Cognitive Intrusion of Pain: scale development and validation

Patients with chronic pain often report their cognition to be impaired by pain, and this observation has been supported by numerous studies measuring the effects of pain on cognitive task performance. Furthermore, cognitive intrusion by pain has been identified as one of 3 components of pain anxiety, alongside general distress and fear of pain. Although cognitive intrusion is a critical characteristic of pain, no specific measure designed to capture its effects exists. In 3 studies, we describe the initial development and validation of a new measure of pain interruption: the Experience of Cognitive Intrusion of Pain (ECIP) scale. In study 1, the ECIP scale was administered to a general population sample to assess its structure and construct validity. In study 2, the factor structure of the ECIP scale was confirmed in a large general population sample experiencing no pain, acute pain, or chronic pain. In study 3, we examined the predictive value of the ECIP scale in pain-related disability in fibromyalgia patients. The ECIP scale scores followed a normal distribution with good variance in a general population sample. The scale had high internal reliability and a clear 1-component structure. It differentiated between chronic pain and control groups, and it was a significant predictor of pain-related disability over and above pain intensity. Repairing attentional interruption from pain may become a novel target for pain management interventions, both pharmacologic and nonpharmacologic.

Methods and Instruments to Evaluate Cognitive Function in Chronic Pain Patients: A Systematic Review

OBJECTIVE

We aimed to systematically review the methods and instruments used to evaluate cognitive function in chronic pain (CP) patients.

METHODS

A sensitive search strategy was designed using five databases. Based on the objectives and methodology, we selected cross-sectional studies on adults with chronic non-cancer pain in which cognitive function was assessed using validated instruments. The characteristics of the subjects, control groups, and other variables that might affect cognitive function, and the instruments used, were extracted from each article.

RESULTS

In the 42 articles identified, 53 instruments were used to assess cognitive function. Chronic pain criteria were defined in 83.3% of the articles and more than half (57.1%) included single diagnosis samples, with fibromyalgia being the most frequent studied (75%). Patients with prior cognitive impairment were excluded in 61.9% of the studies, and a control group was included in 64.3% of the studies. In most cases potential confounding variables were evaluated. More than 14% of the studies used self-report measures, and 73.8% used neuropsychological instruments, particularly for assessing attention (30%) and memory (27.5%). None of the instruments were specifically validated for pain patients and only five studies analyzed the psychometric properties of the instruments.

CONCLUSIONS

Various instruments and methods were used to assess cognitive function in CP patients, particularly fibromyalgia patients, but also other cohorts with well-defined CP. The instruments used had been validated, but not for pain populations, thus they require specific adaptation and validation to be used in CP patients. Certain recommendations are made in order to improve the evaluation of cognitive function in these patients.

Fibromyalgia, Fibro Fog, and Exercise

Fibro fog causes serious problems for those with fibromyalgia syndrome. The mechanisms that cause it have not been well identified. Since prescription medication and other conventional medical interventions have proven less than satisfactory, and while waiting for more investigational information, research suggests that exercise might be helpful.

Fibrofog and fibromyalgia: a narrative review and implications for clinical practice

Patients with fibromyalgia often report forgetfulness as well as declines in cognitive function, memory, and mental alertness-symptoms that have been termed "fibrofog" in popular and electronic media as well as in professional literature. "Fibrofog" is the subjectively experienced cognitive dysfunction associated with fibromyalgia and is a clinically important yet comparatively less well-studied aspect of the disorder; it includes loss of mental clarity (mental fogginess) as well as attention and memory impairment. Although until recently cognitive symptoms have been largely ignored, these symptoms can be more disturbing than the widespread pain and can change these patients' lives, sometimes dramatically so. Whereas widespread musculoskeletal pain, tenderness, and fatigue may be the hallmark symptoms of fibromyalgia, patients rank cognitive dysfunction highly in terms of disease impact. This review addresses (1) the prevalence of self-reported cognitive disturbances in fibromyalgia, (2) the clinical presentation of fibrofog, (3) neuropsychological test performance, with particular attention to discrepancies between self-report and test results, (3) clinical correlates of impaired cognitive function in fibromyalgia, (4) neurobiology relevant to cognitive disturbances in fibromyalgia, and (5) clinical management of fibrofog. Although the pathophysiology of fibromyalgia remains an enigma, evidence suggests that it may be a brain disorder, with cognitive deficits ("fibrofog") reflecting disturbed centrally mediated processes.

Effects of milnacipran on neurocognition, pain, and fatigue in fibromyalgia: a 13-week, randomized, placebo-controlled, crossover trial

OBJECTIVE

To investigate whether milnacipran is safe and effective in improving cognitive function in patients with fibromyalgia.

METHOD

Patients were randomly assigned to receive milnacipran or placebo for 6 weeks, followed by a 1-week washout and then crossover to the other arm for another 6 weeks. The overall trial lasted 13 weeks and was conducted between July 2011 and May 2013. Assessments were performed at each visit. Neurocognition was measured by the Brief Assessment of Cognition (BAC) and MATRICS. Pain was assessed by the visual analog scale (VAS) for pain. Global assessment of fibromyalgia symptoms was measured by the Fibromyalgia Impact Questionnaire (FIQ) and tender point examination. Depression was assessed by the Beck Depression Inventory (BDI). Fatigue was assessed by the Fatigue Severity Scale. Functional outcome was evaluated by the Health Assessment Questionnaire. The Clinical Global Impressions-Severity of Illness (CGI-S) and Improvement (CGI-I) scales and the Patients Clinical Global Impression of Change were used to measure the global impression of severity and improvement.

RESULTS

26 subjects were screened, and 20 subjects completed the trial. The change in verbal memory (P = .001) and the composite T score (P = .044) of the BAC and the change in the attention-vigilance domain T score (P = .042) were significantly improved, but there were no differences between the drug and placebo groups. The changes in the CGI-S scores were not significant, but the changes in the Clinical Impression-Improvement (CGI-I) scores showed worsening in the placebo group at week 1 (P = .032), week 2 (P = .024), week 4 (P = .024), and week 6 (P = .60) compared to baseline. The change in FIQ scores was not significant.

CONCLUSIONS

Milnacipran may have a potential role in the improvement of pain, disability, and mood. The effect of milnacipran on cognition in fibromyalgia needs further research.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01829243.

Phenylephrine alteration of cerebral blood flow during orthostasis: effect on n-back performance in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) with orthostatic intolerance is characterized by neurocognitive deficits and impaired working memory, concentration, and information processing. In CFS, upright tilting [head-up tilt (HUT)] caused decreased cerebral blood flow velocity (CBFv) related to hyperventilation/hypocapnia and impaired cerebral autoregulation; increasing orthostatic stress resulted in decreased neurocognition. We loaded the baroreflex with phenylephrine to prevent hyperventilation and performed n-back neurocognition testing in 11 control subjects and 15 CFS patients. HUT caused a significant increase in heart rate (109.4 ± 3.9 vs. 77.2 ± 1.6 beats/min, P < 0.05) and respiratory rate (20.9 ± 1.7 vs. 14.2 ± 1.2 breaths/min, P < 0.05) and decrease in end-tidal CO2 (ETCO2; 42.8 ± 1.2 vs. 33.9 ± 1.1 Torr, P < 0.05) in CFS vs. control. HUT caused CBFv to decrease 8.7% in control subjects but fell 22.5% in CFS. In CFS, phenylephrine prevented the HUT-induced hyperventilation/hypocapnia and the significant drop in CBFv with HUT (-8.1% vs. -22.5% untreated). There was no difference in control subject n-back normalized response time (nRT) comparing supine to HUT (106.1 ± 6.9 vs. 97.6 ± 7.1 ms at n = 4), and no difference comparing control to CFS while supine (97.1 ± 7.1 vs 96.5 ± 3.9 ms at n = 4). However, HUT of CFS subjects caused a significant increase in nRT (148.0 ± 9.3 vs. 96.4 ± 6.0 ms at n = 4) compared with supine. Phenylephrine significantly reduced the HUT-induced increase in nRT in CFS to levels similar to supine (114.6 ± 7.1 vs. 114.6 ± 9.3 ms at n = 4). Compared with control subjects, CFS subjects are more sensitive both to orthostatic challenge and to baroreflex/chemoreflex-mediated interventions. Increasing blood pressure with phenylephrine can alter CBFv. In CFS subjects, mitigation of the HUT-induced CBFv decrease with phenylephrine has a beneficial effect on n-back outcome.

Cognitive performance in irritable bowel syndrome: evidence of a stress-related impairment in visuospatial memory

BACKGROUND

Central nervous system (CNS) dysfunction is a prominent feature of the functional gastrointestinal (GI) disorder, irritable bowel syndrome (IBS). However, the neurobiological and cognitive consequences of key pathophysiological features of IBS, such as stress-induced changes in hypothalamic-pituitary-adrenal (HPA)-axis functioning, is unknown. Our aim was to determine whether IBS is associated with cognitive impairment, independently of psychiatric co-morbidity, and whether cognitive performance is related to HPA-axis function.

METHOD

A cross-sectional sample of 39 patients with IBS, a disease control group of 18 patients with Crohn's disease (CD) in clinical remission and 40 healthy age- and IQ-matched control participants were assessed using the Paired Associates Learning (PAL), Intra-Extra Dimensional Set Shift (IED) and Spatial Working Memory (SWM) tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a computerized Stroop test. HPA-axis function was determined by measuring the cortisol awakening response (CAR).

RESULTS

IBS patients exhibited a subtle visuospatial memory deficit at the PAL six- pattern stage (p = 0.03), which remained after psychiatric co-morbidity was controlled for (p = 0.04). Morning cortisol levels were lower in IBS (p = 0.04) and significantly associated with visuospatial memory performance within IBS only (p = 0.02).

CONCLUSIONS

For the first time, altered cognitive function on a hippocampal-mediated test of visuospatial memory, which was related to cortisol levels and independent of psychiatric co-morbidity, has been identified in IBS. Visuospatial memory impairment may be a common, but currently neglected, component of IBS. Further elucidation of the nature of this impairment may lead to a greater understanding of the underlying pathophysiology of IBS, and may provide novel therapeutic approaches.

Effect of moderate to vigorous physical activity on long-term clinical outcomes and pain severity in fibromyalgia

OBJECTIVE

To evaluate the relationship between long-term maintenance of moderate to vigorous physical activity (MVPA) and clinical outcomes in fibromyalgia (FM).

METHODS

Patients with FM (n = 170) received individualized exercise prescriptions and completed baseline and followup physical activity assessments using the Community Health Activities Model Program for Seniors questionnaire at weeks 12, 24, and 36. The primary outcome was the change in the Fibromyalgia Impact Questionnaire-Physical Impairment (FIQ-PI) score. The secondary outcomes included improvements in overall well-being (FIQ total score), pain severity ratings, and depression.

RESULTS

Using a threshold increase in MVPA of ≥10 metabolic equivalent hours/week above usual activities, 27 subjects (15.9%) increased and sustained (SUS-PA), 68 (40%) increased but then declined (UNSUS-PA), and 75 (44.1%) did not achieve (LO-PA) this benchmark. Compared to LO-PA subjects, both SUS-PA and UNSUS-PA subjects reported greater improvement in FIQ-PI (P < 0.01) and FIQ total score (P < 0.05). Additionally, the SUS-PA group reported greater improvement in pain severity compared to the LO-PA group (P < 0.05). However, there were no significant group differences between SUS-PA and UNSUS-PA for any primary or secondary outcome measure.

CONCLUSION

Increased participation in MVPA for at least 12 weeks improved physical function and overall well-being in patients with FM. Although sustained physical activity was not associated with greater clinical benefit compared with unsustained physical activity, these findings also suggest that performing greater volumes of physical activity is not associated with worsening pain in FM. Future research is needed to determine the relationship between sustained MVPA participation and subsequent improvement in patient outcomes.

The neuropsychiatric and neuropsychological features of chronic fatigue syndrome: revisiting the enigma

The aim of this article is to provide a comprehensive and updated review of the key neuropsychiatric and neuropsychological complaints associated with chronic fatigue syndrome (CFS). Neuropsychiatric and neuropsychological difficulties are common in CFS and are linked primarily to disorders of mood, affect and behaviour. The neuropsychiatric complaint most frequently encountered amongst CFS patients is depression and in particular major depressive disorder (MDD). Despite decades of research, the precise aetiological relationship between CFS and MDD remains poorly understood. This has resulted in the development of a number of interesting and polarised hypotheses regarding the aetiological nature of CFS. Recent scientific advances have however begun to unravel a number of interesting inflammatory and immunological explanations that suggest CFS and MDD are distinct yet interrelated conditions. The possibility that the overlap between CFS and MDD might be explained in terms of shared oxidative and nitrosative (IO&NS) pathways is an area of intense research interest and is reviewed in detail in this article. The overlap between CFS and MDD is further differentiated by variations in HPA axis activity between the two disorders. Important immunological differences between MDD and CFS are also reviewed with particular emphasis on antiviral RNase L pathways in CFS. In addition to the presence of neuropsychiatric complaints, CFS is also associated with neuropsychological symptoms such as impaired attention, memory and reaction time. The key neuropsychological problems reported by CFS patients are also included in the review in an effort to understand the significance of cognitive impairment in CFS.

Unilateral repetitive transcranial magnetic stimulation of the motor cortex does not affect cognition in patients with fibromyalgia

Repetitive transcranial magnetic stimulation (rTMS) induces changes in neuronal activity that may affect cognition. We assessed cognitive functions, in patients with fibromyalgia participating in a sham-controlled randomized trial of rTMS for pain management. We randomly assigned 38 non depressed fibromyalgia patients (American College of Rheumatology criteria) to the active (n = 20) and sham (n = 18) rTMS treatment groups, in a double-blind manner. rTMS was applied to the left primary motor cortex (10 Hz at 80% of rest motor threshold). Neuropsychological tests were performed immediately before stimulation, to evaluate episodic memory, selective and divided attention and executive functions at baseline, week 3 (after 7 rTMS sessions) and week 11 (after 11 rTMS sessions). The actively treated and sham-treated groups were similar in terms of clinical and neuropsychological variables at baseline. No difference in overall neuropsychological performance with respect to baseline was found between these two groups, but a significant improvement over time was observed in the rTMS group, for several measurements of attention/executive function (the Symbol Digit Modalities Test and the Stroop Color Word Test). Unilateral rTMS of the motor cortex over a three-month period did not modify cognitive functions in patients with chronic pain. rTMS may have mild beneficial cognitive effects, but confirmation is required in larger groups of patients.

Cognitive performance in women aged 50 years and older with and without fibromyalgia

OBJECTIVES

Persons with fibromyalgia (FM) report having cognitive dysfunction. Neuropsychological performance was compared across a variety of domains in 43 women with FM (Mage = 63 years) and in 44 women without FM (Mage = 65 years).

METHOD

Measures included explicit memory (Consortium to Establish a Registry for Alzheimer's Disease [CERAD] immediate/delayed recall, delayed recognition), aspects of executive function including interference/inhibition (Stroop Color/Word test), working memory (Digit Span Forward/Backward), set-shifting/complex sequencing (Trails B), monitoring (verbal fluency: naming animals), processing speed (Trails A, Digit Symbol Substitution Coding), and problem solving (Everyday Problems Test).

RESULTS

Women with FM performed more poorly than controls on executive function (Stroop Color/Word) and one processing speed measure (Digit Symbol Substitution Coding).

DISCUSSION

Results partly support altered cognitive function in FM. Mixed findings across cognitive domains among individuals with or without FM is consistent with the literature and suggest that factors beyond those typically controlled for (e.g., heterogeneity in FM) may be influencing findings. Future research is warranted.

A systematic review of chronic fatigue syndrome: don't assume it's depression

OBJECTIVE

Chronic fatigue syndrome (CFS) is characterized by profound, debilitating fatigue and a combination of several other symptoms resulting in substantial reduction in occupational, personal, social, and educational status. CFS is often misdiagnosed as depression. The objective of this study was to evaluate and discuss different etiologies, approaches, and management strategies of CFS and to present ways to differentiate it from the fatigue symptom of depression.

DATA SOURCES

A MEDLINE search was conducted to identify existing information about CFS and depression using the headings chronic fatigue syndrome AND depression. The alternative terms major depressive disorder and mood disorder were also searched in conjunction with the term chronic fatigue syndrome. Additionally, MEDLINE was searched using the term chronic fatigue. All searches were limited to articles published within the last 10 years, in English. A total of 302 articles were identified by these searches. Also, the term chronic fatigue syndrome was searched by itself. This search was limited to articles published within the last 5 years, in English, and resulted in an additional 460 articles. Additional publications were identified by manually searching the reference lists of the articles from both searches.

STUDY SELECTION AND DATA EXTRACTION

CFS definitions, etiologies, differential diagnoses (especially depression) and management strategies were extracted, reviewed, and summarized to meet the objectives of this article.

DATA SYNTHESIS

CFS is underdiagnosed in more than 80% of the people who have it; at the same time, it is often misdiagnosed as depression. Genetic, immunologic, infectious, metabolic, and neurologic etiologies were suggested to explain CFS. A biopsychosocial model was suggested for evaluating, managing, and differentiating CFS from depression.

CONCLUSIONS

Evaluating and managing chronic fatigue is a challenging situation for physicians, as it is a challenging and difficult condition for patients. A biopsychosocial approach in the evaluation and management is recommended. More studies about CFS manifestations, evaluation, and management are needed.

Neck pain from a rheumatologic perspective

This article provides a comprehensive review of rheumatologic considerations for a clinician when evaluating a patient with neck pain. Clearly, anatomic derangements of the cervical spine should be considered when a patient complains of cervicalgia. However, one must also entertain the possibility of a systemic illness as the cause of the pain. Examples of diseases that may present with a prominent feature of neck pain are discussed, including rheumatoid arthritis, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis, myositis, and fibromyalgia. Evidence of an underlying rheumatic illness may guide the clinician in a different therapeutic direction.

Altered associative learning and emotional decision making in fibromyalgia

OBJECTIVE

The present study examines the possibility that a chronic pain condition, such as fibromyalgia, was associated with deficits in decision making and associative learning.

METHODS

Fifteen patients with fibromyalgia (aged 42-59 years) and 15 healthy controls (aged 39-61 years) participated in the experiment. Subjects completed anxiety (STAI) and depression (BDI) questionnaires, as well as standardized neuropsychological tests (Stroop and WAIS subscales). In addition, an emotional decision-making task (Iowa Gambling Task) and a conditional associative learning task (CALT) were administered to all participants.

RESULTS

Results indicated that fibromyalgia had a poorer performance than healthy controls in both tasks, showing more perseveration errors in the learning task, and more disadvantageous decisions, as well as a more random behavior in the gambling task. Moreover, we observed that poor performance on the associative learning task was mediated by depression, whereas performance on the gambling task was not influenced by depression. No group differences were found on the standardized neuropsychological tests.

CONCLUSION

These findings indicate that pain and depressive symptoms in fibromyalgia might lead to significant deficits in emotionally charged cognitive tasks. Furthermore, it suggests that chronic pain might impose a high cost on executive control, undermining mainly affective processes involved in learning, memory, attention, and decision-making.

Validity and reliability of community health activities model program for seniors and short-form international physical activity questionnaire as physical activity assessment tools in patients with fibromyalgia

PURPOSE

There currently is a paucity of well-validated instruments to quantitatively measure physical activity (PA) levels in patients with fibromyalgia syndrome (FMS). This study aims to determine the construct validity and test-retest reliability of two self-report physical activity questionnaires [short-form international physical activity questionnaire (s-IPAQ) and community health activities model program for seniors (CHAMPS)] in a fibromyalgia population.

METHODS

Thirty subjects (mean age 49.1 +/- 9.6 years; 90% females) who met the American College of Rheumatology criteria for FMS were invited to participate in the study. Two-week test-retest reliability was evaluated for the CHAMPS and s-IPAQ. Construct validity was evaluated by comparing PA reported from these questionnaires with data obtained from accelerometry (steps/week, counts/week) and the 6-minute walk test (6-MWT).

RESULTS

CHAMPS showed greater test-retest reliability (r = 0.58; p < 0.001) compared with s-IPAQ (r = 0.18; p = 0.15). No significant correlations were observed between the self-report PA questionnaires and the 6-MWT or accelerometry data (p > 0.05).

CONCLUSIONS

In a fibromyalgia population, the s-IPAQ does not appear to be a reliable and valid PA assessment tool. CHAMPS displayed moderate test-retest reliability; however, no associations were found between CHAMPS and objectives measures of PA. In view of the known benefits of exercise in patients with FMS, there is a need to develop new measures or validate other existing well-established PA questionnaires.

Do fall predictors in middle aged and older adults predict fall status in persons 50+ with fibromyalgia? An exploratory study

We explored potential predictors of fall status in 70 community-dwelling persons > or =50 years of age with fibromyalgia (FM). Over 40% of the sample reported one or more falls in the year prior to the study. A logistic regression model using 10 variables known to predict falls in middle aged and older persons predicted 45% of the variance in fall status. Three variables offered significant independent contributions to the overall model predicting fall status: perception of postural instability, balance performance, and executive function processing speed. The results support prior work in both nonclinical and clinical populations of middle aged and older adults indicating that falls are associated with multiple risk factors. Prospective designs with larger samples are needed to (a) validate and extend these findings, and (b) identify risk factors related to fall status that are unique to persons with FM.

Investigating health-related quality of life, mood and neuropsychological test performance in a homogeneous cohort of Irish female hepatitis C patients

Neurocognitive dysfunction has been reported in individuals with chronic hepatitis C (CHC) infection, but HCV populations investigated have often included participants with numerous potential confounding comorbidities. This pilot study sought to investigate functional capacity and neurocognitive function in a homogeneous state-infected HCV population with histologically defined mild liver disease, free from the comorbid factors typically associated with HCV populations. A further aim was to examine cognitive function in a treatment naive population with a similar history of iatrogenic HCV exposure and spontaneous viral clearance. A convenience sample of 29 women, all of whom were carefully screened to exclude relevant comorbidities, was recruited to the study. Twenty women with a history of iatrogenic HCV exposure were recruited from prospective specialist tertiary care liver clinics. A comparison group of healthy controls (n = 9) was also assessed. Study participants underwent mood, health-related quality of life and neuropsychological assessment. CHC patients reported significantly higher levels of cognitive fatigue than healthy controls (F = 3.4, P = 0.04). On cognitive testing, CHC patients showed impairments compared with healthy controls on estimates of general memory [F(2,25) = 4.1, P = 0.03, partial eta squared = 0.25], delayed auditory recognition [F(2,25) = 4.2, P = 0.03, partial eta squared= 0.22] and sustained attention [F(2,25) = 3.6, P = 0.04, partial eta squared = 0.22]. Increased cognitive fatigue only correlated with delayed auditory memory recall ability (r = 0.724, P = 0.006). In conclusion, these findings appear to support the presence of neurocognitive abnormalities in an iatrogenically infected, homogeneous female HCV population who were carefully screened to eliminate other factors affecting neurocognitive test performance and may indicate underlying neurophysiological causative mechanisms.

Milnacipran: beyond a role of antidepressant

Milnacipran is a serotonin and norepinephrine reuptake inhibitor (SNRI) with negligible effects on any presynaptic or postsynaptic receptors. Milnacipran has unique pharmacokinetic and pharmacodynamic characteristics that distinguish it from the other marketed serotonin and norepinephrine reuptake inhibitors, venlafaxine, desvenlafaxine, and duloxetine such as equipotent serotonin and norepinephrine reuptake inhibition and a linear dose-concentration trend at therapeutic doses. The half-life of milnacipran is approximately 8 hours. In addition, milnacipran does not inhibit the cytochrome P 450 system, indicating minimal propensity for drug-drug interactions. The antidepressant efficacy of milnacipran has been clearly established in a number of randomized, double-blind, placebo-controlled clinical trials, and it has been widely used for treating major depressive disorder. Moreover, evidence suggests that milnacipran is effective and tolerable in the treatment of fibromyalgia and may have usefulness for fatigue and anxiety symptoms. The current paper reviews researches conducted to date that is relevant to the efficacy, tolerability, and mechanism of action of milnacipran in the treatment of depression, fibromyalgia, and other psychiatric syndromes. Future directions of research are also identified.

Fibromyalgia syndrome module at OMERACT 9: domain construct

The objective of the module was to (1) establish a core domain set for fibromyalgia (FM) assessment in clinical trials and practice, (2) review outcome measure performance characteristics, (3) discuss development of a responder index for assessment of FM in clinical trials, (4) review objective markers, (5) review the domain of cognitive dysfunction, and (6) establish a research agenda for outcomes research. Presentations at the module included: (1) Results of univariate and multivariate analysis of 10 FM clinical trials of 4 drugs, mapping key domains identified in previous patient focus group: Delphi exercises and a clinician/researcher Delphi exercise, and breakout discussions to vote on possible essential domains and reliable measures; (2) Updates regarding outcome measure status; (3) Update on objective markers to measure FM disease state; and (4) Review of the issue of cognitive dysfunction (dyscognition) in FM. Consensus was reached as follows: (1) Greater than 70% of OMERACT participants agreed that pain, tenderness, fatigue, patient global, multidimensional function and sleep disturbance domains should be measured in all FM clinical trials; dyscognition and depression should be measured in some trials; and stiffness, anxiety, functional imaging, and cerebrospinal fluid biomarkers were identified as domains of research interest. (2) FM domain outcome measures have generally proven to be reliable, discriminative, and feasible. More sophisticated and comprehensive measures are in development, as is a responder index for FM. (3) Increasing numbers of objective markers are being developed for FM assessment. (4) Cognitive dysfunction assessment by self-assessed and applied outcome measures is being developed. In conclusion, a multidimensional symptom core set is proposed for evaluation of FM in clinical trials. Research on improved measures of single domains and composite measures is ongoing.

Physical performance as a predictor of attention and processing speed in fibromyalgia

Cherry BJ, Weiss J, Barakat BK, Rutledge DN, Jones CJ. Physical performance as a predictor of attention and processing speed in fibromyalgia.

OBJECTIVE

To explore the associations between physical (both self-report and objective measures) and cognitive function for persons with fibromyalgia (FM).

DESIGN

Correlational study.

SETTING

An exercise testing laboratory in southern California.

PARTICIPANTS

Community-residing and functionally independent (not wheelchair-bound) adults meeting the American College of Rheumatology 1990 criteria for FM (N=51) with a mean age of 54 years and no history of stroke.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Composite Physical Function Scale, Fibromyalgia Impact Questionnaire, adapted Trail Making Test parts A (TMT-A) and B (TMT-B), Digit Symbol Substitution Test, a composite index of TMT-A, TMT-B, and Digit Symbol Substitution Test combined, and physical performance assessments.

RESULTS

Hierarchical regression analyses indicated that better objective physical performance predicted increased cognitive function for TMT-A and the composite cognitive score after controlling for age and symptom burden. That is, as the physical performance level decreased, cognitive performance levels decreased.

CONCLUSIONS

Findings suggest that research is needed to determine whether patterns of physical activity participation, through their effects on physical fitness and performance, can enhance cognitive performance in persons with FM. Physiologic changes in specific brain regions in FM (eg, hippocampus, neural pain regions) suggest that further research is also warranted in determining specific relationships between biomarkers and cognitive performance in persons with FM.

Developmental influences on medically unexplained symptoms

BACKGROUND

Medically unexplained (or 'functional') symptoms (MUS) are physical symptoms that prompt the sufferer to seek healthcare but remain unexplained after an appropriate medical evaluation. Examples of MUS also occur in veterinary medicine. For example, domestic cats suffer a syndrome comparable to interstitial cystitis, a chronic pelvic pain syndrome of humans.

METHOD

Review of current evidence suggests the hypothesis that developmental factors may play a role in some cases of MUS. Maternal perception of a threatening environment may be transmitted to the fetus when hormones cross the placenta and affect fetal physiology, effectively 'programming' the fetal stress response system and associated behaviors toward enhanced vigilance. After birth, intense stress responses in the individual may result in similar vulnerability, which may be unmasked by subsequent stressors.

RESULTS

Epigenetic modulation of gene expression (EMGEX) appears to play a central role in creation of this 'survival phenotype'. The recent development of techniques to identify the presence of EMGEX provides new tools to investigate these questions, and drugs and other interventions that may reverse EMGEX are also under active investigation.

CONCLUSION

Viewing MUS from the perspective of underlying developmental influences involving EMGEX that affect function of a variety of organs based on familial (genetic and environmental) predispositions rather than from the traditional viewpoint of isolated organ-originating diseases has at least two important implications: it provides a parsimonious explanation for findings heretofore difficult to reconcile, and it opens whole new areas of investigation into causes and treatments for this class of disorders.