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  1. A Fo Ben
  1. Correspondence to Dr A Fo Ben; rhys-thomas{at}

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Vaccine trials and tribulations

Decades of vaccine scepticism predicated on a deep human fear of injectable toxins means that people expect a reaction from vaccines. What better way to survey the rate and scope of these than looking at the placebo arm of the COVID-19 jab trials? A systematic review and meta-analysis of 12 articles (45 380 participants) showed that 35% of people receiving their first placebo jab experienced a serious adverse event (32% with the second dose). The most commonly reported problems in the placebo groups were headache (19% first dose, 16% second) and fatigue (first dose: 17%, 15% second). There were more reactions in the genuine vaccine arm—but allowing for such a hefty nocebo response this accounts for 76% of all adverse events from the first jab (52% of the second).

JAMA Netw Open. 2022;5 (1):e2143955.

Multiple sclerosis, single cause?

Bad luck if you were doing research into the causes of MS, it has all been completed now. Hand your P45s in and pack your bags. Do not let A Fo Ben’s tongue in cheek comment detract from a blockbuster clinical research paper on a 20-year cohort of US military recruits, 10 million in all (955 of whom developed MS). Their risk of developing MS was 32-fold higher after Epstein-Barr virus (EBV) infection, but not following other viruses, including CMV. Serum levels of neurofilament light chain increased only after EBV seroconversion. The strength of this association means a confounder would need to have a greater than 60-fold risk of causing MS, a greater than 60-fold risk of EBV seroconversion. When do we start vaccination against MS? And then we can redeploy the MS doctors?

Science. 2022;375 (6578):296–301.

Cat nip prevents bugs that nip

Have you ever wondered why cats are so attracted to catnip? They rub their faces and heads against catnip (Nepeta cataria) and silver vine (Actinidia polygama) and then roll about on the floor. Authors (who I have to admit are much more curious about this than I have ever been) have been rewarded with a surprising answer. They identified iridoid nepetalactol is the major component of silver vine that elicits this potent response which increases plasma β-endorphin levels. The rubbing behaviour transfers nepetalactol onto feline faces and heads where it repels the mosquito, Aedes albopictus. The authors suggest that this attraction and behavioural response is a neurophysiological chemical pest defence that protects dear moggy from mosquito bites.

Sci Adv. 2021 Jan 20;7 (4):eabd9135.

If it is all in your mind, then it is all in your brain also

A recent systematic review of biomarkers for pathological dissociation (because we all dissociate a little) identified 205 unique studies. The key structural biomarkers were decreased hippocampal volume, basal ganglia volume and thalamus volume (figure 1). Functional differences are seen across related regions including the prefrontal cortex, bilateral superior frontal regions, anterior cingulate, posterior association areas and basal ganglia. Neuroimaging is currently the most attractive modality for studying pathological disassociation, in the absence of psychophysiological and genetic biomarkers.

Figure 1

Systematic review of neuroimaging markers of pathological dissociation. Sections B (limbic and subcortical regions) and C (lobar) demonstrating the frequency of findings as increase, decrease, a positive or a negative correlation, or ‘none’.

Neurosci Biobehav Rev. 2021;123:120–202.


  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

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