Siblings of Fibromyalgia Patients Have Heightened Pain Sensitivity

SAN ANTONIO – Women with fibromyalgia and their siblings experience a generalized sensitivity to pain and lower levels of serum serotonin, according to new research.

These are the preliminary results of an ongoing study, said Dr. Laurence A. Bradley, who presented the study at the annual meeting of the American Pain Society.

Several recent studies have shown that first-degree relatives of women with fibromyalgia have higher lifetime rates of major depressive and anxiety disorders, compared with first-degree relatives of those with rheumatoid arthritis. Other research has found that fibromyalgia and reduced pressure pain thresholds aggregate in families.

“Some studies show that female relatives of the fibromyalgia probands display higher rates of psychiatric disorders than do male relatives,” said Dr. Bradley, who is a professor of medicine in the division of clinical immunology and rheumatology at the University of Alabama, Birmingham.

The goal of the current study was to measure pain sensitivity and blood serum levels of serotonin in female patients with fibromyalgia, sex-matched healthy controls, and the siblings of both the fibromyalgia probands and the controls.

It is unknown if the first-degree relatives of women with fibromyalgia exhibit the same pain sensitivity, Dr. Bradley explained, and if there are differences in the expression of serotonin in these relatives as well as in the patients. It is also unclear to what degree serotonin levels may mediate differences in pain sensitivity, not only in patients vs. controls but also in relatives of patients vs. relatives of controls.

Thus far, the study has enrolled 49 families, and includes 16 probands with fibromyalgia; 5 male and 11 female proband siblings; 23 female, pain-free, control individuals; and 8 male and 15 female control siblings. All of the participants had blood drawn for measurement of serum serotonin, and underwent testing for pain thresholds. Pain sensitivity was measured after stimulation of pressure points and control points. Thermal heat and ischemic pain threshold tolerance was also evaluated in all study participants.

The pain threshold and serum serotonin levels were measured between probands vs. controls and proband siblings vs. control siblings. Dr. Bradley and his colleagues also evaluated the group differences in pain thresholds after controlling for the influence of serotonin.

“We found that not only were pain thresholds lower in probands as compared with healthy controls, but we also saw the same pattern in proband relatives as compared with the relatives of the control group,” Dr. Bradley said. Lower levels of serum serotonin also were seen in both the patients and their siblings, compared with controls.

However, analysis revealed that serum serotonin levels partially mediated these group differences in pain threshold only for ischemic stimulation. Thus, serotonin appears to have a limited influence on pressure and thermal pain thresholds.

“The fact that we found only a modest relationship between ischemic pain thresholds and serotonin in patient probands and controls helps explain why early studies using tricyclic antidepressants and pressure point stimulation found no changes in pain response,” Dr. Bradley said. In future studies, “we need to look at multiple factors such as differences in family environments and gene variances,” he said.

SAN ANTONIO – Women with fibromyalgia and their siblings experience a generalized sensitivity to pain and lower levels of serum serotonin, according to new research.

These are the preliminary results of an ongoing study, said Dr. Laurence A. Bradley, who presented the study at the annual meeting of the American Pain Society.

Several recent studies have shown that first-degree relatives of women with fibromyalgia have higher lifetime rates of major depressive and anxiety disorders, compared with first-degree relatives of those with rheumatoid arthritis. Other research has found that fibromyalgia and reduced pressure pain thresholds aggregate in families.

“Some studies show that female relatives of the fibromyalgia probands display higher rates of psychiatric disorders than do male relatives,” said Dr. Bradley, who is a professor of medicine in the division of clinical immunology and rheumatology at the University of Alabama, Birmingham.

The goal of the current study was to measure pain sensitivity and blood serum levels of serotonin in female patients with fibromyalgia, sex-matched healthy controls, and the siblings of both the fibromyalgia probands and the controls.

It is unknown if the first-degree relatives of women with fibromyalgia exhibit the same pain sensitivity, Dr. Bradley explained, and if there are differences in the expression of serotonin in these relatives as well as in the patients. It is also unclear to what degree serotonin levels may mediate differences in pain sensitivity, not only in patients vs. controls but also in relatives of patients vs. relatives of controls.

Thus far, the study has enrolled 49 families, and includes 16 probands with fibromyalgia; 5 male and 11 female proband siblings; 23 female, pain-free, control individuals; and 8 male and 15 female control siblings. All of the participants had blood drawn for measurement of serum serotonin, and underwent testing for pain thresholds. Pain sensitivity was measured after stimulation of pressure points and control points. Thermal heat and ischemic pain threshold tolerance was also evaluated in all study participants.

The pain threshold and serum serotonin levels were measured between probands vs. controls and proband siblings vs. control siblings. Dr. Bradley and his colleagues also evaluated the group differences in pain thresholds after controlling for the influence of serotonin.

“We found that not only were pain thresholds lower in probands as compared with healthy controls, but we also saw the same pattern in proband relatives as compared with the relatives of the control group,” Dr. Bradley said. Lower levels of serum serotonin also were seen in both the patients and their siblings, compared with controls.

However, analysis revealed that serum serotonin levels partially mediated these group differences in pain threshold only for ischemic stimulation. Thus, serotonin appears to have a limited influence on pressure and thermal pain thresholds.

“The fact that we found only a modest relationship between ischemic pain thresholds and serotonin in patient probands and controls helps explain why early studies using tricyclic antidepressants and pressure point stimulation found no changes in pain response,” Dr. Bradley said. In future studies, “we need to look at multiple factors such as differences in family environments and gene variances,” he said.

SAN ANTONIO – Women with fibromyalgia and their siblings experience a generalized sensitivity to pain and lower levels of serum serotonin, according to new research.

These are the preliminary results of an ongoing study, said Dr. Laurence A. Bradley, who presented the study at the annual meeting of the American Pain Society.

Several recent studies have shown that first-degree relatives of women with fibromyalgia have higher lifetime rates of major depressive and anxiety disorders, compared with first-degree relatives of those with rheumatoid arthritis. Other research has found that fibromyalgia and reduced pressure pain thresholds aggregate in families.

“Some studies show that female relatives of the fibromyalgia probands display higher rates of psychiatric disorders than do male relatives,” said Dr. Bradley, who is a professor of medicine in the division of clinical immunology and rheumatology at the University of Alabama, Birmingham.

The goal of the current study was to measure pain sensitivity and blood serum levels of serotonin in female patients with fibromyalgia, sex-matched healthy controls, and the siblings of both the fibromyalgia probands and the controls.

It is unknown if the first-degree relatives of women with fibromyalgia exhibit the same pain sensitivity, Dr. Bradley explained, and if there are differences in the expression of serotonin in these relatives as well as in the patients. It is also unclear to what degree serotonin levels may mediate differences in pain sensitivity, not only in patients vs. controls but also in relatives of patients vs. relatives of controls.

Thus far, the study has enrolled 49 families, and includes 16 probands with fibromyalgia; 5 male and 11 female proband siblings; 23 female, pain-free, control individuals; and 8 male and 15 female control siblings. All of the participants had blood drawn for measurement of serum serotonin, and underwent testing for pain thresholds. Pain sensitivity was measured after stimulation of pressure points and control points. Thermal heat and ischemic pain threshold tolerance was also evaluated in all study participants.

The pain threshold and serum serotonin levels were measured between probands vs. controls and proband siblings vs. control siblings. Dr. Bradley and his colleagues also evaluated the group differences in pain thresholds after controlling for the influence of serotonin.

“We found that not only were pain thresholds lower in probands as compared with healthy controls, but we also saw the same pattern in proband relatives as compared with the relatives of the control group,” Dr. Bradley said. Lower levels of serum serotonin also were seen in both the patients and their siblings, compared with controls.

However, analysis revealed that serum serotonin levels partially mediated these group differences in pain threshold only for ischemic stimulation. Thus, serotonin appears to have a limited influence on pressure and thermal pain thresholds.

“The fact that we found only a modest relationship between ischemic pain thresholds and serotonin in patient probands and controls helps explain why early studies using tricyclic antidepressants and pressure point stimulation found no changes in pain response,” Dr. Bradley said. In future studies, “we need to look at multiple factors such as differences in family environments and gene variances,” he said.