, reported researchers in a small retrospective case-control study.
Delusions of parasitosis (DOP) affects mostly middle-aged women and has associations with renal failure and some medications, wrote corresponding author Colleen Reisz, MD, a dermatologist with the department of internal medicine at the University of Missouri–Kansas City School of Medicine, and her coauthors. The study was published online December 15, 2023, in the Journal of the American Academy of Dermatology.
“We hypothesize that vulnerability to DOP emerges when multiple factors combine, such as age, sex, medications, and changes in [drug] clearance capacity,” Dr. Reisz and her coauthors wrote. “Changes in health care, such as the dramatic increase in stimulant prescriptions and alternatives to opioids in pain management, may be contributing to off target drug effects on the brain.”
To test their hypothesis, the researchers conducted a case-control study of biometric and pharmaceutical data from 34 patients with DOP which they compared to an age-matched control group of 53 women presenting with a dermatitis above the clavicle from a general dermatology practice between 2012 and 2020. They de-identified the data and performed statistical analysis on variables that included biometric data and intake of pharmaceuticals and nutraceuticals. Polypharmacy was defined as five or more drugs.
Of the 34 patients with DOP, 27 were women with a mean age of 58 years and 7 were men with a mean age of 60 years. Dr. Reisz and her colleagues observed statistical significance between cases and controls in terms of polypharmacy (P = .011), attention-deficit/hyperactivity disorder medications (P < .001), selective serotonin reuptake inhibitors (P = .005), opioids (P = .003), and gabapentin (P = .003).
In other findings, half of DOP cases presented with samples of perceived parasitic material, and four associated the perceived infestation with a single emotion-laden event. This prompted the researchers “to consider that DOP may share mechanisms with fear conditioning and extinction,” they wrote. “Fear conditioning refers to the process of memory acquisition and extinction. This process is essential for survival and has been studied in posttraumatic stress disorder.”
They acknowledged certain limitations of the study, including its retrospective single-center design and the lack of control for factors such as socioeconomic background and level of education.
“Patients with DOP should undergo detailed drug histories and examination of clearance profiles, especially renal function,” the researchers concluded.
Evan A. Rieder, MD, a New York City–based dermatologist and psychiatrist who was asked to comment on the study, said that delusional infestation is one of the most difficult medical conditions to treat and study.
Dr. Rieder
Dr. Evan A. Rieder
“Though the numbers of cases in this research letter are small, they are instructive in demonstrating a high burden of polypharmacy including psychostimulants, opioids, and SSRIs in such patients,” he told this news organization. “Dermatologists should be performing detailed drug histories, obtaining comprehensive lab work, and considering the effects of medications — both illicit and prescribed — on clinical presentations. While in many cases, delusional patients refuse to consent to psychopharmacologic medications (or treatment in general), the elimination or decrease in dose of certain problematic medications may be helpful in and of themselves.”
The researchers reported having no financial disclosures. Dr. Rieder disclosed that he is a consultant for AbbVie, L’Oréal, Pierre Fabre, Procter & Gamble, and Unilever.