Type of study: Case-control

The finding: Somatic symptom disorder patients exhibited selective volume reductions in specific cortico-limbic regions of the brain which are involved in the circuitry of pain and emotional processing. Worse symptomatology correlated with greater reductions in specific grey matter volumes in frontal-limbic and parietal regions. These results suggest a potential unique neuro-anatomic correlate for somatic symptom disorder.

Strength and weaknesses: This the first study to specifically examine associations between grey matter volume changes in patients with somatic symptom disorder and clinical (including cognitive) measures.

The limitations include a relatively small sample size which could have limited the statistical power of analyses, as well as a study population which might not be generalizable to all somatic symptom disorder patients since it included only hospitalized patients as well as some patients with no pain. Information was not collected about the duration of illness and any psychiatric meds the patients may have been taking, which could have potentially influenced observed brain changes. Neuro-psychological testing was not performed in healthy controls, which did not allow normative data for comparison to the performance of somatic symptom disorder patients and thus ultimately limits the inferential power of the results.

Relevance: Identifying specific biological markers in somatic symptom disorder may have significant implications for designing more targeted, effective treatment options.

Type of study: Case control

The finding: This study revealed a clear, statistically significant association between increasing patient-reported, chart-documented adverse drug reactions (or “polyallergy”) and various demographic, diagnostic, pharmacological, and health care utilization trends, namely: higher degrees of health care utilization, increased rates of psychiatric and functional somatic syndrome diagnoses, and increased odds of use of psychotropic agents.

Strength and weaknesses: The study was powered by a very large clinical sample (over 2 million patients, allowing for detection of statistically significant associations despite multiple potential confounders. It also included a naturalistic group of all patients with a documented clinical encounter within a given large medical system over a period of greater than half a decade. Distinct data were examined across multiple realms (demographic, medical, psychiatric, pharmacologic, and health care utilization), providing a multi-dimensional understanding of patients with polyallergy.

Limitations of the study include a retrospective design restricting examined data, as well as the crude capture of documented allergies—some of which might not be verified, and which could be highly patient- and operator-dependent in documentation. Clinician behavior is a complex and important confounder which could potentially have impacted allergy documentation. The allergy count cohort definitions were also arbitrary, even after sensitivity analysis. Patients were limited to one clinical site, which could also affect the generalizability of the results. Health care utilization is a complex metric, and utilization outside of the one site was not available. Finally, medications that were listed under certain groups of illnesses might have been used for indications other than that specific category (e.g., benzos prescribed for seizures rather than anxiety).

Relevance: This study demonstrates that the presence of polyallergy/multiple chemical sensitivity may signal accompanying psychopathology and/or abnormal illness behaviour. Understanding this association could potentially impact management of patients with polyallergy, including educating them about non-immune mediated sensitivities. This could, in turn, lead to a transparent re-evaluation of allergy lists that might otherwise unnecessarily complicate clinical care.