IR Sant Pau Study Proposes Dimensional Shift for Depression Diagnosis

Researchers at the Sant Pau Research Institute have published a scientific review proposing a shift away from broad psychiatric diagnostic categories toward a dimensional approach focused on specific symptoms and underlying neurobiological mechanisms. Published in Translational Psychiatry, the study examines resting-state functional brain connectivity to map major depression symptoms to distinct neural circuits.

Limitations of Traditional Depression Diagnoses in Clinical Practice

In clinical practice, diagnosing major depressive disorder relies on symptom combinations defined by international diagnostic manuals, such as the Diagnostic and Statistical Manual of Mental Disorders developed by the American Psychiatric Association. This system establishes a minimum number of required symptoms but permits numerous possible combinations under a single clinical label. This diagnostic flexibility creates substantial heterogeneity among patients who share a formal diagnosis yet present with divergent clinical profiles. This diversity complicates the identification of consistent brain biomarkers and the prediction of treatment responses.

“When we use a single diagnostic category for people with very different symptoms, it becomes much more difficult to identify clear brain correlates or anticipate which treatment may work best in each case,” said Dr. Marta Cano, a researcher with the Mental Health group at IR Sant Pau and co-author of the study.

Cano added, “Analyzing depression through specific clinical dimensions allows us to examine more precisely the brain mechanisms underlying each symptom and better understand why the experience of the disorder differs so much from one patient to another.”

Neurofunctional Signatures Across Four Clinical Dimensions

The review evaluates studies utilizing resting-state functional magnetic resonance imaging, a technique used to analyze how different brain regions communicate when a subject performs no specific task. This approach targets persistent, self-referential mental processes relevant to depression. Based on existing evidence, the study concentrates on four clinical dimensions: anhedonia, rumination, insomnia, and suicidal behavior.

In the analysis of anhedonia—defined as difficulty experiencing pleasure—the review separates consummatory anhedonia, related to immediate pleasure, from anticipatory anhedonia, linked to motivation and reward expectation. Consummatory anhedonia consistently correlates with reduced connectivity between the ventral striatum and prefrontal cortex regions involved in hedonic valuation. Anticipatory anhedonia displays more complex connectivity patterns, indicating the two processes rely on partially distinct brain circuits.

Rumination is evaluated as a pattern of repetitive, self-referential thinking split into maladaptive rumination, or brooding, and reflective rumination. Brooding associates primarily with increased connectivity within the default mode network, whereas reflective rumination engages executive networks related to cognitive control. Insomnia is highlighted not as a secondary complaint, but as a core dimension of depression.

“The aim of this study is to change the way we interpret depression from the perspective of the brain, moving from a single diagnosis toward the identification of circuits associated with specific symptoms,” Cano said. “This approach allows us to better account for the clinical diversity we see every day in patient care.”