Hayes agreed, and explained how his team tried to account for that: They looked at whether mentally ill patients fared any better when they had prescriptions for a diuretic (a high blood pressure drug).
There is existing evidence that statins, calcium channel blockers and metformin may, in theory, have mental health benefits. In contrast, there is no similar evidence for diuretics. So, Hayes explained, if medication use is simply a marker of better health care — or more stability in patients’ lives — then those on diuretics should also do better.
It turned out they didn’t.
“So this goes against the argument that what we observe is just related to a greater period of stability,” Hayes said.
The results are based on medical records from 142,691 Swedish adults and teenagers who were treated for schizophrenia, bipolar disorder or non-affective psychosis in the years 2005 through 2016.
The researchers focused on patients’ use of statins, calcium channel blockers or metformin because of the evidence those drugs might ease mental health symptoms.
Statins, for instance, are anti-inflammatory, and various psychiatric disorders are thought to involve inflammation in the central nervous system, according to Hayes. Plus, animal research has hinted that statins might have antipsychotic effects or protect brain cells from damage.
Metformin, meanwhile, might help address problems in the way the brain uses glucose (sugar) in people with certain mental disorders. For their part, calcium channel blockers target so-called L-type calcium channels — which exist not only in the heart and blood vessels, but in the brain. And animal research suggests they help control emotional behavior.
Overall, the investigators found, patients were less likely to be admitted to a psychiatric hospital during periods where they had prescriptions for any of those medications, versus other times.
They were also less likely to self-harm, which includes suicide attempts.
The study, published online Jan. 9 in JAMA Psychiatry, was funded by government and foundation grants.
“At this stage,” Hayes said, “we are not suggesting people with these mental illnesses change their treatment.”
But, he added, if they do have health conditions that warrant taking a statin, calcium channel blocker or metformin, then perhaps they should.