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Researchers at Stanford Medicine have described a novel subtype of depression known as the cognitive biotype, which affects 27 per cent of people with depression but is unresponsive to treatment with antidepressants that are frequently administered.
These patients' cognitive abilities to plan ahead, exhibit self-control, maintain concentrate despite distractions, and suppress inappropriate behaviour were shown to be compromised by cognitive activities; imaging revealed decreased activity in two brain regions in charge of those functions. SSRIs, or selective serotonin reuptake inhibitors, are antidepressants that target serotonin and are frequently prescribed by doctors since depression is typically thought of as a mood disease. However, these medications are less beneficial for individuals who have cognitive dysfunction. According to research, treating these cognitive dysfunctions with antidepressants that are less widely prescribed or other therapies may help with symptoms relief and the restoration of social and occupational capacities. Leanne Williams, PhD, the Vincent V.C. Woo Professor and professor of psychiatry and behavioural sciences, is the senior author of the study, which was released on June 15 in JAMA Network Open. She claims that the study is a part of a larger endeavour by neuroscientists to discover treatments that target certain depression biotypes. "One of the big challenges is to find a new way to address what is currently a trial-and-error process so that more people can get better sooner," Williams said. "Bringing in these objective cognitive measures like imaging will make sure we're not using the same treatment on every patient." Finding the biotype In the study, 1,008 adults with previously unmedicated major depressive disorder were randomly given one of three widely prescribed typical antidepressants: escitalopram (brand name Lexapro) or sertraline (Zoloft), which act on serotonin, or venlafaxine-XR (Effexor), which acts on both serotonin and norepinephrine. Seven hundred and twelve of the participants completed the eight-week regimen. Before and after treatment with the antidepressants, the participants' depressive symptoms were measured using two surveys -- one, clinician-administered, and the other, a self-assessment, which included questions related to changes in sleep and eating. Measures on social and occupational functioning, as well as quality of life, were tracked as well. The participants also completed a series of cognitive tests, before and after treatment, measuring verbal memory, working memory, decision speed and sustained attention, among other tasks. Before treatment, scientists scanned 96 of the participants using functional magnetic resonance imaging as they engaged in a task called the "GoNoGo" that requires participants to press a button as quickly as possible when they see "Go" in green and to not press when they see "NoGo" in red. The fMRI tracked neuronal activity by measuring changes in blood oxygen levels, which showed levels of activity in different brain regions corresponding to Go or NoGo responses. Researchers then compared the participants' images with those of individuals without depression. The researchers found that 27% of the participants had more prominent symptoms of cognitive slowing and insomnia, impaired cognitive function on behavioral tests, as well as reduced activity in certain frontal brain regions -- a profile they labeled the cognitive biotype. "This study is crucial because psychiatrists have few measurement tools for depression to help make treatment decisions," said Laura Hack, MD, PhD, the lead author of the study and an assistant professor of psychiatry and behavioral sciences. "It's mostly making observations and self-report measures. Imaging while performing cognitive tasks is rather novel in depression treatment studies." Pre-treatment fMRI showed those with the cognitive biotype had significantly reduced activity in the dorsolateral prefrontal cortex and dorsal anterior cingulate regions during the GoNoGo task compared with the activity levels in participants who did not have the cognitive biotype. Together, the two regions form the cognitive control circuit, which is responsible for limiting unwanted or irrelevant thoughts and responses and improving goal selection, among other tasks. After treatment, the researchers found that for the three antidepressants administered, the overall remission rates -- the absence of overall depression symptoms -- were 38.8% for participants with the newly discovered biotype and 47.7% for those without it. This difference was most prominent for sertraline, for which the remission rates were 35.9% and 50% for those with the biotype and those without, respectively. "Depression presents in different ways in different people, but finding commonalities -- like similar profiles of brain function -- helps medical professionals effectively treat participants by individualizing care," Williams said. Depression isn't one size fits all Williams and Hack propose that behavior measurement and imaging could help diagnose depression biotypes and lead to better treatment. A patient could complete a survey on their own computer or in the doctor's office, and if they are found to display a certain biotype, they might be referred to imaging for confirmation before undergoing treatment. Researchers at the Stanford Center for Precision Mental Health and Wellness, which Williams directs, in partnership with the Stanford Translational Precision Mental Health Clinic, which Hack directs, are studying another medication -- guanfacine -- that specifically targets the dorsolateral prefrontal cortex region with support from Stanford University Innovative Medicines Accelerator. They believe this treatment could be more effective for patients with the cognitive subtype. Williams and Hack hope to conduct studies with participants who have the cognitive biotype, comparing different types of medication with treatments such as transcranial magnetic stimulation and cognitive behavioral therapy. In transcranial magnetic stimulation, commonly referred to as TMS, magnetic fields stimulate nerve cells; in cognitive behavioral therapy, patients are taught to use problem-solving strategies to counter negative thoughts that contribute to both emotional dysregulation and loss of social and occupational abilities. "I regularly witness the suffering, the loss of hope and the increase in suicidality that occurs when people are going through our trial-and-error process," Hack said. "And it's because we start with medications that have the same mechanism of action for everyone with depression, even though depression is quite heterogeneous. I think this study could help change that." (ANI)
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