Researchers at NYU Langone Health have built a phone game that can spot signs of major depressive disorder in as little as three minutes by tracking how long a person keeps trying when rewards start to shrink. The study was published on May 18 in the Proceedings of the National Academy of Sciences.
The game asks players to collect apples from digital trees. With each round of picking, a tree gives fewer apples, and the software records the moment a player decides the smaller harvest is no longer worth the trouble and moves to a new tree. That switch-over point is what the researchers measure.
In a study of 120 people, 50 diagnosed with major depression and 70 without, those with depression gave up on the fading reward about 50% sooner than healthy participants. Healthy players usually stayed until a tree dropped to around five apples. Depressed players left much earlier, when the tree still had eight or nine apples, depending on how severe their symptoms were.
The task measures anhedonia, a loss of pleasure felt by roughly 70% of people with major depression. The researchers believe that depression shifts the brain's internal benchmark for what counts as rewarding, so things that normally feel good end up feeling flat or negative. The game taps into a known connection between anhedonia and a brain region called the anterior cingulate cortex, which helps set expectations.
Screenshot: The game the scientists designed to potentially detect depression in participants.
A second task asked participants to bid on snack foods. When healthy people bid on their favourite snacks and then on a mixed list, their sense of value shifted for a while but soon returned to normal. In depressed patients, that sense of value stayed stuck in the shifted position and never recovered.
"Patients with depression do not seem to be able to adapt their expectations normally as conditions change, which gives us a hint about what is wrong mechanistically in their brains," said co-first author Aadith Vittala, an MD/PhD student at the NYU Grossman School of Medicine, in a press release on the findings. "This looks to us like a therapeutic target, and we are already checking to see if a behavioural therapy or a drug might be able to fix this reference point stickiness."
Co-senior author Paul W. Glimcher, chair of the Department of Neuroscience, said in the press release that the game works a bit like measuring blood pressure. "Our behavioural game gives us clues to what is happening in the brains of patients with depression, which we hope will let us identify them as reliably as finding heart disease by taking someone's blood pressure," he said.
The game can be played remotely, and its accuracy matches that of standard tests that usually need several in-person clinic visits, the study authors said. Co-senior author Dan Iosifescu, a professor of psychiatry, explained in the press release that tracking a patient's reference points could help doctors identify a particular type of depression tied to anhedonia and adjust treatment more quickly. "We may be able to do this remotely by asking patients, rather than travelling repeatedly for in-person visits, to spend a few minutes per week playing a smartphone game that lets us quickly adjust their treatment," he said. The study was funded by the National Institute of Mental Health.
