Based on a meta-analysis of 11 studies.
In what the researchers say is the first meta-analysis to compare the levels of cortisol, a common stress hormone, with the stage of schizophrenia a patient is suffering from, the team found a link between cortisol and psychosis.
Meta-analyses like this one are particularly compelling because they compile data from multiple studies, in this case 11 studies with sample sizes ranging from 26 to 68. While a single study may be susceptible to random effects, a meta-analysis looks at data from a large number of participants, making it a powerful tool for deciphering results.
Dr. Zoltan Sarnyai, an associate professor at James Cook University who led the analysis, says that this finding may eventually help doctors identify which patients will develop full-blown psychosis among those who show early stages of the disease.
"Only some 20 to 30 per cent of individuals who are at high-risk of developing psychosis due to their clinical presentation or family history actually do so,” Sarnyai explained in a press release. “Identifying those people early is where the cortisol measurement comes in.”
The researchers looked at the different levels of cortisol after waking up in the morning, called Cortisol Awakening Response (CAR), and compared the data to healthy controls.
Study co-author Dr. Maximus Berger said that scientists have long suspected that cortisol plays a role in psychotic disorders, but some study results had been contradictory — until now.
"We were able to show that patients with psychosis fail to produce cortisol after they wake up in the morning. We found this even in patients with recent onset of the illness," said Dr Berger.
In the paper, which has been published in the journal Neuroscience & Biobehavioral Reviews, the researchers write that a link between blunted CAR and schizophrenia pathophysiology comes from previous human studies which found that individuals with blunted CAR have reduced grey matter volume and increased stress-related activity in particular brain regions associated with psychosis.
An important limitation that the researchers note in their write-up is that, while the included studies were consistent in their methodology, none used an objective verification of saliva sampling.
Still, the researchers believe that looking at biomarkers, like CAR, can prove to be a successful technique in medicine.
"Biomarkers are very few and far between in psychiatry, so even though a huge amount of work is still needed, this could become a valuable technique," said Sarnyai.
He explains that low CAR levels can also indicate a risk for other chronic diseases and have been linked to systemic inflammation, suggesting that there’s a potential for early diagnosis and treatment of those conditions as well.
“Future studies on cortisol alterations in patients with psychosis should use longitudinal designs to further determine the potential use of CAR as a biomarker with predictive value,” the team concluded.
You might also like: Can the Brain Fight off Schizophrenia?