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French fries are comfort food for many. But reaching for fried foods may have a negative impact on mental health. 

A research team in Hangzhou, China, found that frequent consumption of fried foods, especially fried potatoes, was linked with a 12% higher risk of anxiety and 7% higher risk of depression than in people who didn't eat fried foods. 

Fried foods are known risk factors for obesity, high blood pressure and other health effects. These results "open an avenue in the significance of reducing fried food consumption for mental health," according to the paper published Monday in the journal PNAS. 

However, experts who study nutrition said the results are preliminary, and it's not necessarily clear whether the fried foods were driving mental health issues, or people experiencing symptoms of depression or anxiety turned to fried foods. 

The study evaluated 140,728 people over 11.3 years. After excluding participants diagnosed with depression within the first two years, a total of 8,294 cases of anxiety and 12,735 cases of depression were found in those that consumed fried food, while specifically fried potatoes were found to have a 2% increase in risk of depression over fried white meat. 

The study had also found that the participants consuming more than one serving of fried food regularly were more likely to be younger men. 

Unhealthy food and poor nutrition can lower one's mood and progress a mental health condition, as found in a prior study cited within this new one. 

In the new study, the researchers suggest that acrylamide, a chemical formed during the frying process, especially in fried potatoes, is to blame for the higher risk of anxiety and depression. 

In a separate paper referenced in the new study, the researchers exposed zebrafish to the chemical, finding that long-term exposure had caused the fish to dwell in dark zones within the tank, a common sign of a higher anxiety level in the fish. 

The zebrafish had also displayed a reduced ability to explore their tanks and socialize, as they did not swim closely with other zebrafish, even though zebrafish are known to form schools with their species. 

"The health effects of fried food will depend greatly on what food is fried and what type of fat is used for frying," said Willett, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health, via email. "Potatoes are a concern for possible effects of mood because they can cause large surges in blood sugar and then hormonal responses to these surges. However, these surges are partly blunted by fat, which would be provided by the fat from frying." 

Willett also noted that acrylamide isn't only produced by frying. It's in coffee, because of the roasting of the beans, and in toast, because "heating carbohydrates together with protein can do this." 

Zhejiang University researcher Yu Zhang, an author of the study, said in an email that "there is no need to panic about the adverse effects of fried food." But maintaining a healthy lifestyle and reducing consumption of fried foods may be helpful for mental health in addition to overall health.

The researchers had pointed to a recent rise in depression and anxiety worldwide, with 2020 seeing an increase of 27.6% and 25.6%, respectively. The World Health Organization also estimates that more than 5% of adults suffer from depression, globally, as noted in the paper.