Reading the Mind in the Blood

When it comes to diagnosis and prognosis, mental health conditions are among the most elusive. What works perfectly for one patient may fail utterly or even make the problem worse for another, and the range of medications available to treat disorders like depression is ever-broadening. At the moment, doctors treat through trial and error, prescribing one type of antidepressant after another until they strike upon the one that works for a given patient. There’s currently no better way of doing it – but that may be about to change. Researchers from King’s College London have developed a potential blood test to determine whether or not patients with depression are likely to respond to conventional treatments.

The test measures the absolute mRNA values of two inflammatory factors, macrophage migration inhibitory factor (MIF) and interleukin-1β (1). In an initial sample of 142 patients, those who exhibited higher concentrations of the two biomarkers were less likely to respond to standard treatments like selective serotonin reuptake inhibitors or tricyclic antidepressants (see Figure 1). It’s possible that inflammation interferes with biochemical and neurological functions required for antidepressant function in some individuals, while others may have genetic differences that affect both inflammation and drug response. To find out more, the researchers will need to expand their work to larger and more varied patient cohorts before bringing the test to the clinic.

Carmine Pariante, principal investigator on the study, estimates that about one-third of patients exhibit levels of inflammatory marker mRNA above the established cutoffs. Those are the patients he encourages to seek more aggressive treatment – perhaps by prescribing a less common drug, or by combining depression treatment with anti-inflammatory medication. He said, “We would not want to go on prescribing too much medicine if it’s not necessary, but we would want to escalate people sooner rather than later if they need it. (2)”.