Machine learning uncovers early warning signs of depression in brain scans

A new computational model combined with brain imaging data reveals that relying too heavily on prior expectations when perceiving facial expressions can predict a person’s risk for developing depression. By analyzing how the human brain processes angry faces, researchers identified a mathematical pattern of visual distortion that appears up to four years before clinical symptoms emerge. The study was published in Science Advances.

Major depressive disorder affects millions of people worldwide and is often difficult to treat once established. Early detection remains a high priority for public health experts, but predicting who will develop the condition relies mostly on self-reported symptoms and environmental risk factors. Identifying biological markers that indicate an individual’s vulnerability before they feel ill could improve prevention efforts.

Mental health conditions are often characterized by altered emotional processing, such as a tendency to interpret ambiguous social cues as negative or threatening. Leading psychological theories propose that our brains construct emotional experiences by using abstract concepts stored in our memory to interpret raw sensory information, like the visual details of a face. In recent years, researchers have mapped out various brain regions associated with depression, but these descriptive patterns do not explain the exact mechanisms driving the illness.

Han Lu and Qiang Luo, researchers at Shenzhen University and Fudan University, respectively, sought to understand how this integration of sensory input and abstract memory might go wrong in people prone to depression. They hypothesized that the visual cortex, the brain region responsible for processing sight, might act as an early bottleneck where social threat signals become distorted. To test this idea, the researchers developed a mathematical simulation to replicate how the human brain learns to recognize emotional expressions.

The researchers first analyzed functional magnetic resonance imaging brain scans from 1,332 nineteen-year-old participants in a population-based European study known as the IMAGEN cohort. This imaging technique measures blood flow in the brain to detect areas of neural activity. The scans tracked the adolescents’ brain activity while they viewed short video clips of faces transitioning from neutral expressions to angry ones.

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Using a machine learning algorithm, the research team extracted a mathematical representation of how each participant’s visual cortex encoded the angry faces. They refer to this specific pattern of neural activity as a visual code. The team then grouped the participants based on the efficiency of these visual codes, separating them into one group with typical, highly efficient visual encoding and another with inefficient, noisy visual processing.

Adolescents in the less efficient group reported higher levels of emotional symptoms, such as anxiety and low mood, on clinical questionnaires. This relationship indicated that a degraded visual representation of angry faces was tied to emotional distress. The researchers determined that poor visual coding in the brain was directly related to the presence of emotional symptoms.

To understand the computational mechanism behind this degraded visual processing, the team built a deep neural network, which is an artificial intelligence model composed of interconnected algorithms modeled after the human brain. This specific model featured two distinct processing pathways. One pathway processed raw visual information from images, while the other pathway held abstract conceptual knowledge about different emotions.

In standard human perception, the brain uses abstract knowledge to guide and speed up the processing of visual information, allowing a person to recognize a facial expression quickly. The researchers programmed their artificial network to mimic this process, allowing the conceptual pathway to regulate the visual pathway as the model learned to identify facial expressions. When the researchers compared the artificial network’s internal mathematical code to the human brain scans, they found a strong alignment.

This similarity suggested the model successfully replicated the visual perception of angry faces. The team then conducted an experiment on the model by altering the strength of the conceptual pathway’s influence over the visual pathway. They systematically turned the regulation strength up and down to observe how the network would respond.

When the regulation was set to an intermediate level, the model achieved optimal emotion recognition. However, when the researchers forced the model to apply excessive conceptual regulation, it began to misclassify neutral faces as angry or sad. This overreliance on abstract concepts overrode the actual visual details, producing a computational negative bias.

The internal code of this overly regulated artificial model closely matched the inefficient, noisy brain patterns found in the adolescents with higher emotional symptoms. This suggests that overregularization, which is the act of letting preexisting beliefs overpower sensory reality, acts as a mechanism that drives negative emotional biases.

Building on this simulation, the researchers created a computational marker that quantified each human participant’s degree of visual overregularization based on their brain scans at age nineteen. They then followed up with 725 of these participants four years later. The goal was to see if the marker could forecast the onset of mental health issues.

Among the young adults who had no clinical symptoms at age nineteen, the mathematical marker successfully predicted which individuals would develop high levels of emotional symptoms by age twenty-three. This prediction model outperformed traditional baseline measures that rely only on demographics and basic brain activation levels. The finding suggests that the overregulation mechanism may precede the onset of emotional symptoms.

To determine if this computational mechanism was specific to depression, the team examined genetic data from the IMAGEN participants. They checked for associations between the overregulation marker and genetic variants tied to various psychiatric conditions. The analysis showed a link between the overregulated visual marker and a specific genetic variant associated with major depressive disorder, located on a gene involved in brain development.

The marker was also linked to the participants’ polygenic risk score for depression, which is a number that summarizes the estimated effect of many different genetic variants on a person’s risk for a disease. The visual marker did not show any links to the genetic risks for alcohol use disorder or eating disorders. This specificity supported the idea that the visual distortion mechanism is uniquely tied to depression.

Finally, the researchers tested their marker in a separate clinical dataset of young adults to see if it persisted in established illnesses. They analyzed brain scans from 134 patients diagnosed with major depressive disorder and 62 healthy control subjects. The patients with depression exhibited higher levels of the overregulation marker compared to the healthy controls.

The marker accurately classified whether a participant had depression or not. When applied to patients with alcohol use disorder, anorexia nervosa, and bulimia nervosa, the marker showed no group differences. The traditional brain activation measures were not statistically significant in distinguishing the depressed patients from the healthy controls.

The study participants from both the population-based and clinical cohorts were predominantly white individuals from middle-to-high socioeconomic backgrounds. Future research will need to examine whether these specific computational patterns apply equally to populations with different ethnic, racial, and socioeconomic demographics. The differences in emotional symptoms between the high-efficiency and low-efficiency visual processing groups in the general adolescent sample were also relatively small.

While expected in general population studies capturing subclinical distress, this small effect size means the visual clustering approach alone has limited diagnostic power for individual patients at this stage. Researchers must validate the broader clinical utility of this marker in independent patient groups. Tracking these computational markers in younger adolescents could reveal if the visual distortions appear even earlier in development.

Tracking patients over time will also help determine if the marker can predict long-term recovery versus chronic illness. Identifying whether the visual distortion is a permanent trait or a temporary state would assist in designing targeted therapies. Interventions that aim to retrain visual processing might one day help mitigate this depression risk.

The study, “Deep learning reveals a neurocomputational mechanism predicting depression risk in adolescents,” was authored by Han Lu, Xiaoqian Yan, Benjamin Becker, Andreas Heinz, Barbara J. Sahakian, Christelle Langley, Zhaoyu Zuo, Luolong Cao, Zuo Zhang, Lauren Robinson, Nilakshi Vaidya, Jeanne Winterer, Sinead King, Charlotte Walton, Tobias Banaschewski, Gareth J. Barker, Arun L.W. Bokde, Rüdiger Brühl, Herta Flor, Hugh Garavan, Penny Gowland, Antoine Grigis, Herve Lemaitre, Jean-Luc Martinot, Marie-Laure Paillère Martinot, Eric Artiges, Frauke Nees, Dimitri Papadopoulos Orfanos, Luise Poustka, Hedi Kebir, Ulrike Schmidt, Julia Sinclair, Michael N. Smolka, Sarah Hohmann, Nathalie Holz, Henrik Walter, Robert Whelan, Sylvane Desrivières, Gunter Schumann, Qiang Luo, STRATIFY/ESTRA Consortium, and IMAGEN Consortium.