Risk Of Chronic Fatigue Syndrome Research Articles

Increased risk of chronic fatigue syndrome following infection: a 17-year population-based cohort study

BackgroundPrevious serological studies have indicated an association between viruses and atypical pathogens and Chronic Fatigue Syndrome (CFS). This study aims to investigate the correlation between infections from common pathogens, including typical bacteria, and the subsequent risk of developing CFS. The analysis is based on data from Taiwan’s National Health Insurance Research Database.MethodsFrom 2000 to 2017, we included a total of 395,811 cases aged 20 years or older newly diagnosed with infection. The cases were matched 1:1 with controls using a propensity score and were followed up until diagnoses of CFS were made.ResultsThe Cox proportional hazards regression analysis was used to estimate the relationship between infection and the subsequent risk of CFS. The incidence density rates among non-infection and infection population were 3.67 and 5.40 per 1000 person‐years, respectively (adjusted hazard ratio [HR] = 1.5, with a 95% confidence interval [CI] 1.47–1.54). Patients infected with Varicella-zoster virus, Mycobacterium tuberculosis, Escherichia coli, Candida, Salmonella, Staphylococcus aureus and influenza virus had a significantly higher risk of CFS than those without these pathogens (p < 0.05). Patients taking doxycycline, azithromycin, moxifloxacin, levofloxacin, or ciprofloxacin had a significantly lower risk of CFS than patients in the corresponding control group (p < 0.05).ConclusionOur population-based retrospective cohort study found that infection with common pathogens, including bacteria, viruses, is associated with an increased risk of developing CFS.

How mycobacterium tuberculosis infection could lead to the increasing risks of chronic fatigue syndrome and the potential immunological effects: a population-based retrospective cohort study

BackgroundChronic fatigue syndrome (CFS) has been shown to be associated with infections. Tuberculosis (TB) is a highly prevalent infectious disease. Patients with chronic fatigue syndrome and post-tuberculosis experience similar symptoms. Furthermore, chronic fatigue syndrome and tuberculosis share similar plasma immunosignatures. This study aimed to clarify the risk of chronic fatigue syndrome following the diagnosis of Mycobacterium tuberculosis infection (MTI), by analyzing the National Health Insurance Research Database of Taiwan.Methods7666 patients aged 20 years or older with newly diagnosed Mycobacterium tuberculosis infection during 2000–2011 and 30,663 participants without Mycobacterium tuberculosis infection were identified. Both groups were followed up until the diagnoses of chronic fatigue syndrome were made at the end of 2011.ResultsThe relationship between Mycobacterium tuberculosis infection and the subsequent risk of chronic fatigue syndrome was estimated through Cox proportional hazards regression analysis, with the incidence density rates being 3.04 and 3.69 per 1000 person‐years among the non‐Mycobacterium tuberculosis infection and Mycobacterium tuberculosis infection populations, respectively (adjusted hazard ratio [HR] = 1.23, with 95% confidence interval [CI] 1.03–1.47). In the stratified analysis, the Mycobacterium tuberculosis infection group were consistently associated with a higher risk of chronic fatigue syndrome in the male sex (HR = 1.27, 95% CI 1.02–1.58) and age group of ≥ 65 years old (HR = 2.50, 95% CI 1.86–3.38).ConclusionsThe data from this population‐based retrospective cohort study revealed that Mycobacterium tuberculosis infection is associated with an elevated risk of subsequent chronic fatigue syndrome.

Human Herpesvirus 6 Infection and Risk of Chronic Fatigue Syndrome: A Systematic Review and Meta-Analysis

Introduction: Chronic fatigue syndrome (CFS) is a neurological disease that is accompanied by excessive fatigue or tiredness. There are several reports confirming the association between human herpesvirus 6 (HHV-6) infection and CFS illness. This systematic review and meta-analysis was performed to integrate the information of published studies with regard to this association until May 2021. Methods: The literature search was based on keywords including “chronic fatigue syndrome and HHV 6,” “chronic fatigue syndrome and HHV-6,” “chronic fatigue syndrome and HHV6,” “chronic fatigue syndrome and Herpes virus 6,” and “chronic fatigue syndrome and Herpesvirus6” in MEDLINE (PubMed), Web of Science, and EMBASE. Results: The literature search identified 17 studies to be included in the systematic review and 11 studies in meta-analysis. The symmetry funnel plot and Egger’s test (p value = 0.2) identified no publication bias among studies. Moreover, the low level of I² revealed homogeneity across studies. Discussion: In conclusion, the association between the HHV-6 infection and CFS incidence was substantiated. However, the results of this study also suggest that further comprehensive studies are needed to solidify the association between HHV-6 and CFS. Future studies should consider additional factors that may have affected the significance of such a correlation.

Associations of physical and psychiatric conditions with chronic fatigue syndrome in Germany: an exploratory case-control study.

Only a few studies have analyzed the effects of physical and psychiatric conditions on the risk of chronic fatigue syndrome (CFS). Therefore, the goal of this exploratory case-control study was to investigate the associations of physical and psychiatric conditions with CFS in almost 19 800 adults from Germany. This study included patients diagnosed for the first time with CFS in one of 1238 general practices in Germany between 2010 and 2017 (index date). Controls without CFS were matched (1:1) to cases with CFS by sex, age, index year, and practice. Physical and psychiatric conditions diagnosed in the year prior to the index date were included if they were present in at least 3% of patients with CFS. Associations between physical and psychiatric conditions (33 potential independent variables) and CFS (dependent variable) were analyzed in an adjusted conditional logistic regression model, and physical and psychiatric disorders were included in the model using forward stepwise selection. This study included 9896 cases with CFS and 9896 controls without CFS [65.1% women; mean (standard deviation) age 49.5 (18.3) years]. Seven conditions were associated with CFS in the adjusted regression model. The disorders displaying the strongest relationship with CFS were cancer [odds ratio (OR) = 2.57, 95% confidence interval (CI) = 2.24-2.95], sleep disorders (OR = 1.88, 95% CI = 1.66-2.12) and depression (OR = 1.77, 95% CI = 1.61-1.95). Cancer, sleep disorders, and depression were strongly and positively associated with CFS. Additional studies are needed to gain a better understanding of the mechanisms underlying these relationships.

Associations of occupational stress, workplace violence, and organizational support on chronic fatigue syndrome among nurses.

Chronic fatigue syndrome is an agnogenic disease worldwide. Nurses are at a high risk of chronic fatigue syndrome. However, no research has been done to examine the associations of workplace violence, organizational support, and occupational stress with chronic fatigue syndrome among Chinese nurses. This study aimed to examine effects of these factors on chronic fatigue syndrome in this occupational group. Cross-sectional. All participants voluntarily completed a questionnaire survey. The study was conducted in Liaoning province from December 2017-January 2018. Self-administered questionnaires were distributed to 1,200 nurses, including Effort-Reward-Imbalance, Workplace Violence Scale, Survey of Perceived Organizational Support, together with age, gender, marital status, education levels, physical activities, job rank, monthly income, and weekly working hours. Complete responses were obtained from 1,080 (90%) participants. Chronic fatigue syndrome was diagnosed by doctors according to the Centers for Disease Control and Prevention criteria. Multivariable logistic regression was performed to examine these independent risk factors. The prevalence of chronic fatigue syndrome was 6.76%. The results of logistic regression analysis showed that nurses who experienced serious higher levels of overcommitment, workplace violence and less organizational support were more likely to be classified as chronic fatigue syndrome. There was a high prevalence of chronic fatigue syndrome. Lower workplace violence, more organizational support and lower overcommitment could be effective resources for reducing chronic fatigue syndrome. Workplace violence, organizational support, and occupational stress were related to chronic fatigue syndrome, which helped to explain why Chinese nurses suffered higher prevalence of chronic fatigue syndrome. Overcommitment explained chronic fatigue syndrome better than Effort/Reward Ratio, so intrinsic stress played a more critical role than extrinsic stress in chronic fatigue syndrome. Chinese nurses suffered serious sleep disorders and impairment of concentration and memory. These symptoms might also attribute to serious occupational stress, unsafe and unsupportive working environment. Creating a safe and supportive working environment, relieving intrinsic occupational stress should be considered as an institutional strategy to early prevent chronic fatigue syndrome.

Increased risk of chronic fatigue syndrome following psoriasis: a nationwide population-based cohort study

BackgroundThe onset of chronic fatigue syndrome (CFS) has been shown to be associated with several immunological conditions such as infections or atopy. The aim of this study was to clarify the risk of chronic fatigue syndrome following the diagnosis of psoriasis, an immune-related dermatological disease, by analyzing the National Health Insurance Research Database of Taiwan.Method2616 patients aged 20 years or older with newly diagnosed psoriasis during 2004–2008 and 10,464 participants without psoriasis were identified. Both groups were followed up until the diagnoses of CFS were made at the end of 2011.ResultsThe relationship between psoriasis and the subsequent risk of CFS was estimated through Cox proportional hazards regression analysis, with the incidence density rates being 2.27 and 3.58 per 1000 person-years among the non-psoriasis and psoriasis populations, respectively (adjusted hazard ratio [HR] = 1.48, with 95% confidence interval [CI] 1.07–2.06). In the stratified analysis, the psoriasis group were consistently associated with a higher risk of CFS in male sex (HR = 2.05, 95% CI 1.31–3.20) and age group of ≥ 60 years old (HR = 2.32, 95% CI 1.33–4.06). In addition, we discovered that the significantly increased risk of CFS among psoriasis patients is attenuated after they receive phototherapy and/or immunomodulatory drugs.ConclusionsThe data from this population-based retrospective cohort study revealed that psoriasis is associated with an elevated risk of subsequent CFS, which is differentiated by sex and age.

THE IMPORTANCE OF GEROHYGIENE FOR THE IDENTIFICATION AND ASSESSMENT OF OCCUPATIONAL, ENVIRONMENTAL AND SOCIAL RISKS

A consistent criterion and scale are proposed for the identification and comparative evaluation of occupational, environmental and social factors affecting human health. With the aid of the criterion for the annual risk increase (ARI) it is possible to determine harmful effects of factors of the environment by means of the measurement of the rate of the gain in the population risk for chronic health problems. For the hygienic assessment in a unitary scale of ARI values for a number of diseases there are used control and background values characterizing the age-related trend in the risk of these diseases in the absence of harmful exogenous factors. The application of the criteria and ARI scale is illustrated by the data on age dynamics of the risk of chronic bronchitis in dockers-drivers, the dynamics of the risk of long-term diseases with the temporary disability (workers, specialists, leaders of industrial enterprises in acceptable and hazardous conditions), the dynamics of the risk of chronic fatigue syndrome (working in harmful conditions, smoking and non-smoking women, women living near heavy traffic). The amount of the ARI for the chronic fatigue under exposure to occupational and non-occupational can coincide.

Increased risk of chronic fatigue syndrome in patients with inflammatory bowel disease: a population-based retrospective cohort study

BackgroundSimilarities in the symptoms of chronic fatigue syndrome (CFS) and inflammatory bowel disease (IBD) have been observed as follows: severe disease activity in IBD correlates with severe fatigue, major psychiatric signs, the common use of medication, and bacterial translocation. One of several hypotheses for explaining the mechanisms underlying CFS suggests a similarity to the impaired intestinal mucosa of IBD. “This study investigated the risk of incident CFS among patients with IBD”.MethodsWe conducted a population-based retrospective cohort study by using Taiwan’s National Health Insurance Research Database to evaluate the subsequent risk of CFS in patients with IBD, according to demographic characteristics and comorbidities. The exposure cohort comprised 2163 patients with new diagnoses of IBD. Each patient was randomly selected and frequency matching according to gender and age with four participants from the general population who had no history of CFS at the index date (control cohort). Cox proportional hazards regression analysis was conducted to estimate the relationship between IBD and the subsequent risk of CFS.ResultsThe exposure cohort had a significantly higher overall risk of subsequent CFS than that of the control group [adjusted hazard ratio (Christophi in Inflamm Bowel Dis 18(12):2342–2356, 2012) = 2.25, 95%, confidence interval (Aaron and Buchwald in Ann Intern Med 134(9 Pt 2):868–881, 2001; Farraye et al. in Am J Gastroenterol 112:241, 2017) 1.70–2.99]. Further analysis indicated a significantly higher risk of CFS in patients who were male (HR = 3.23, 95% CI 2.12–4.91), were older than 35 years, and had IBD but without comorbidity status, e.g. Cancers, diabetes, obesity, depression, anxiety, sleep disorder, renal disease (HR = 2.50, 95% CI 1.63–3.84) after adjustment.ConclusionThe findings from this population-based retrospective cohort study suggest that IBD, especially Crohn’s disease, is associated with an increased risk of subsequent CFS.

Increased risk of chronic fatigue syndrome following burn injuries

BackgroundThe overlapping symptoms and pathophysiological similarities between burn injury and chronic fatigue syndrome (CFS) are noteworthy. Thus, this study explores the possible association between burn injury and the subsequent risk of CFS.MethodWe used data from the Taiwan National Health Insurance system to address the research topic. The exposure cohort comprised of 17,204 patients with new diagnoses of burn injury. Each patient was frequency matched according to age, sex, index year, and comorbidities with four participants from the general population who did not have a history of CFS (control cohort). Cox proportional hazards regression analysis was conducted to estimate the relationship between burn injury and the risk of subsequent CFS.ResultThe incidence of CFS in the exposure and control cohorts was 1.61 and 0.86 per 1000 person-years, respectively. The exposure cohort had a significantly higher overall risk of subsequent CFS than did the control cohort (adjusted hazard ratio [HR] = 1.48, 95% confidence interval [CI] = 1.41–1.56). The risk of CFS in patients with burn injury in whichever stratification (including sex, age, and comorbidity) was also higher than that of the control cohort.ConclusionThe findings from this population-based retrospective cohort study suggest that thermal injury is associated with an increased risk of subsequent CFS and provided a point of view suggesting burn injuries in sun- exposed areas such as the face and limbs had greater impact on subsequent development of CFS compared with trunk areas. In addition, extensively burned areas and visible scars were predictors of greater physiological and psychosocial that are needed to follow-up in the long run.

Dry eye syndrome and the subsequent risk of chronic fatigue syndrome-a prospective population-based study in Taiwan.

Background and AimThe clinical association between dry eye syndrome (DES) and chronic fatigue syndrome (CFS) remain unclear with less evidences. We aimed to investigate the relationship between CFS and DES using a national insurance and prospective cohort study.MethodsData from the Longitudinal Health Insurance Database 2000 was applied to estimate the incidence of CFS among patients with DES, and their age- and sex-matched controls without DES over a long-term follow-up period. All participants were CFS free at baseline, before the interval (2005–2007), but were later diagnosed with CFS. DES patients and its relative matched controls were excluded prevalent CFS before the same interval.ResultsWe identified 884 patients with DES and 3,536 matched controls in baseline and estimated the hazard ratios for incident CFS in the follow-up period. Patients with DES had a 2.08-fold considerably increasing risk of developing CFS, compared to non-DES group. An elevated risk of developing CFS remained (1.61-fold risk) even after adjusting for age, sex, and comorbidities. There was a presence of increasing risk in DES-related CFS when CFS-related comorbidities existing (adjusted hazard ratio, 1.98, 95% confidence interval, 1.19–3.29; p < 0.01). The subsequent risk for CFS between DES and non-DES patients was significant increased with three or more annual medical visits, the adjusted risk for CFS was 4.88-fold risk (95% CI, 2.26–10.58, p < 0.001).ConclusionWe recommended that physicians should be aware of the increased risk of CFS among DES patients and adequately assess the health impacts among these patients.

Increased risk of chronic fatigue syndrome in patients with migraine: A retrospective cohort study

ObjectiveThe common concurrence of migraine and chronic fatigue syndrome (CFS) has been reported but whether migraine poses a higher risk of CFS remains unknown. In this retrospective case–control study, we examined the association between the 2 disorders by using a nationwide, population-based database in Taiwan. MethodsThe data were retrieved and analyzed from the National Health Insurance Research Database (NHIRD) of Taiwan; 6902 newly diagnosed migraine cases from 2006–2010 were identified in a subset of the NHIRD, and 27,608 migraine-free individuals were randomly selected as the comparison cohort. The multivariate Cox proportional hazards regression model was used to investigate the risk of CFS in migraineurs after adjustment for demographic characteristics and comorbidities. ResultsAfter adjustment for the covariates, the risk of CFS was 1.5-fold higher in the migraine cohort than in the comparison cohort (52.72 vs. 28.85 per 10,000person-years). Intriguingly, the risk was most prominent in the oldest group (≥65years), with a 2.11-fold increased risk (95% confidence interval 1.31–3.41) of CFS. In addition, the adjusted cumulative incidence of CFS in the follow-up years was higher in the migraine group (log-rank test, P<.0001), and CFS incidence appeared to increase with the frequency of migraine diagnoses. ConclusionThe current study demonstrated an increased risk of CFS in migraineurs. Proposed mechanisms in previous studies such as mitochondrial dysfunction and central sensitization may underlie the shared pathophysiology of these seemingly distinct but potentially overlapping disorders.

Increased Risk of Chronic Fatigue Syndrome Following Atopy: A Population-Based Study.

Several hypotheses have been proposed to explain the etiopathogenesis of chronic fatigue syndrome (CFS), including immune dysregulation. However, few population-based prospective cohort studies have been conducted on CFS and atopy. We investigated the relationship between atopy and CFS by using a population-based cohort study.In this prospective, population-based cohort study of the National Health Insurance Research Database, we identified 42,558 patients with atopy and 170,232 patients without atopy from 2005 to 2007 with follow-up to 2011. The incidence rates and risks for CFS were estimated using Cox proportion hazards regression.The overall incidence rate of CFS was higher in the atopy cohort compared with the nonatopy cohort (1.37 versus 0.87 per 1000 person-year), with an adjusted hazard ratio of 1.48 (95% confidence interval 1.30–1.69). The risk of CFS in the atopy cohort increased 1.47- to 1.50-fold for each nonexisting comorbidity. Patients with numerous atopic symptoms exhibited a biological gradient of increasing risk for CFS, and the risk changed significantly after adjustment for age, sex, and comorbidities, increasing from 1.46- to 2.59-fold.We revealed that atopy is associated with CFS, particularly in patients with numerous atopic syndromes. The actual mechanism for CFS development in patients with atopy remains unclear and requires further investigation. We recommend researching the subsequent fatigue symptom in patients with atopy, particularly those with multiple atopic syndromes.

Erratum to: Increased risk of chronic fatigue syndrome following herpes zoster: a population-based study

Erratum to: Increased risk of chronic fatigue syndrome following herpes zoster: a population-based study

Increased risk of chronic fatigue syndrome following herpes zoster: a population-based study

Chronic fatigue syndrome (CFS) is a complex disorder accompanied by unexplainable persistent fatigue, in which several etiological factors exist, such as viral infections. Using the National Health Insurance Research Database (NHIRD) of Taiwan, this study evaluated the association between herpes zoster (HZ) infection and the risk of CFS, and examined the possibility of patients developing postviral fatigue effects, including the possibility of developing other unexplainable chronic fatigue conditions. In this prospective cohort study using the NHIRD, we identified 9,205 patients with HZ infection [ICD-9 (International Classification of Disease, Ninth Revision), code 053] and 36,820 patients without HZ infection (non-HZ) from 2005 to 2007, and followed up to the end of 2010. The incidence rate of CFS was higher in the HZ cohort than in the non-HZ cohort (4.56 vs. 3.44 per 1,000 person-years), with an adjusted hazard ratio of 1.29 [95% confidence interval (CI) = 1.09-1.53]. It was shown that the risk of CFS without comorbidity for each patient increased from 1.25- to 1.36-fold between the CFS and non-CFS cohorts; with long-term follow-up, the HZ cohort showed a significantly higher cumulative incidence rate of developing CFS than the non-HZ patients. We propose that patients with chronic fatigue might exist in a subset of patients that would be associated with HZ infection. The actual mechanism of development of CFS that is attributed to HZ infection remains unclear. The findings of this population cohort study provide pivotal evidence of postviral fatigue among patients with HZ infection.

Cervarix does not increase the risk of chronic fatigue syndrome, says MHRA

Cervarix does not increase the risk of chronic fatigue syndrome, says MHRA

Childhood Trauma and Risk for Chronic Fatigue Syndrome

Childhood trauma appears to be a potent risk factor for chronic fatigue syndrome (CFS). Evidence from developmental neuroscience suggests that early experience programs the development of regulatory systems that are implicated in the pathophysiology of CFS, including the hypothalamic-pituitary-adrenal axis. However, the contribution of childhood trauma to neuroendocrine dysfunction in CFS remains obscure. To replicate findings on the relationship between childhood trauma and risk for CFS and to evaluate the association between childhood trauma and neuroendocrine dysfunction in CFS. A case-control study of 113 persons with CFS and 124 well control subjects identified from a general population sample of 19 381 adult residents of Georgia. Self-reported childhood trauma (sexual, physical, and emotional abuse; emotional and physical neglect), psychopathology (depression, anxiety, and posttraumatic stress disorder), and salivary cortisol response to awakening. Individuals with CFS reported significantly higher levels of childhood trauma and psychopathological symptoms than control subjects. Exposure to childhood trauma was associated with a 6-fold increased risk of CFS. Sexual abuse, emotional abuse, and emotional neglect were most effective in discriminating CFS cases from controls. There was a graded relationship between exposure level and CFS risk. The risk of CFS conveyed by childhood trauma further increased with the presence of posttraumatic stress disorder symptoms. Only individuals with CFS and with childhood trauma exposure, but not individuals with CFS without exposure, exhibited decreased salivary cortisol concentrations after awakening compared with control subjects. Our results confirm childhood trauma as an important risk factor of CFS. In addition, neuroendocrine dysfunction, a hallmark feature of CFS, appears to be associated with childhood trauma. This possibly reflects a biological correlate of vulnerability due to early developmental insults. Our findings are critical to inform pathophysiological research and to devise targets for the prevention of CFS.

Early Adverse Experience and Risk for Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) is an important public health problem. The causes of CFS are unknown and effective prevention strategies remain elusive. A growing literature suggests that early adverse experience increases the risk for a range of negative health outcomes, including fatiguing illnesses. Identification of developmental risk factors for CFS is critical to inform pathophysiological research and devise targets for primary prevention. To examine the relationship between early adverse experience and risk for CFS in a population-based sample of clinically confirmed CFS cases and nonfatigued control subjects. A case-control study of 43 cases with current CFS and 60 nonfatigued controls identified from a general population sample of 56 146 adult residents from Wichita, Kan. Self-reported childhood trauma (sexual, physical, and emotional abuse and emotional and physical neglect) and psychopathology (depression, anxiety, and posttraumatic stress disorder) by CFS status. The CFS cases reported significantly higher levels of childhood trauma and psychopathology compared with the controls. Exposure to childhood trauma was associated with a 3- to 8-fold increased risk for CFS across different trauma types. There was a graded relationship between the degree of trauma exposure and CFS risk. Childhood trauma was associated with greater CFS symptom severity and with symptoms of depression, anxiety, and posttraumatic stress disorder. The risk for CFS conveyed by childhood trauma increased with the presence of concurrent psychopathology. This study provides evidence of increased levels of multiple types of childhood trauma in a population-based sample of clinically confirmed CFS cases compared with nonfatigued controls. Our results suggest that childhood trauma is an important risk factor for CFS. This risk was in part associated with altered emotional state. Studies scrutinizing the psychological and neurobiological mechanisms that translate childhood adversity into CFS risk may provide direct targets for the early prevention of CFS.

Mirrored Symptoms in Mother and Child With Chronic Fatigue Syndrome

Our aim with this study was to assess the relation between chronic fatigue syndrome in adolescents and fatigue and associated symptoms in their fathers and mothers, more specifically the presence of chronic fatigue syndrome-like symptoms and psychologic distress. In this cross-sectional study, 40 adolescents with chronic fatigue syndrome according to the Centers for Disease Control and Prevention criteria were compared with 36 healthy control subjects and their respective parents. Questionnaires regarding fatigue (Checklist Individual Strength), fatigue-associated symptoms, and psychopathology (Symptom Checklist-90) were applied to the children and their parents. Psychologic distress in the mother corresponds with an adjusted odds ratio of 5.6 for the presence of CFS in the child. The presence of fatigue in the mother and dimensional assessment of fatigue with the Checklist Individual Strength revealed odds ratios of, respectively, 5.29 and 2.86 for the presence of chronic fatigue syndrome in the child. An increase of 1 SD of the hours spent by the working mother outside the home reduced the risk for chronic fatigue syndrome in their child with 61%. The fathers did not show any risk indicator for chronic fatigue syndrome in their child. Mothers of adolescents with chronic fatigue syndrome exhibit fatigue and psychologic symptoms similar to their child in contrast with the fathers. The striking difference between the absent association in fathers and the evident association in mothers suggests that the shared symptom complex of mother and child is the result of an interplay between genetic vulnerability and environmental factors.