But you don't need to ditch cured meats yet: The researchers noted that the findings showed only an association between processed meats and manic episodes - the new research didn't prove cause and effect. In the study, some people without a history of psychiatric disorders also consumed meats with nitrates.
The authors of the study published in the journal Molecular Psychiatry hope it will help to prevent mania and develop treatments for mental disorders. They can be found in things like salami, hot dogs, jerky, bacon and lunch meats, though those products can sometimes be purchased nitrate-free.
The dietary survey did not ask about frequency or time frame of cured meat consumption, so the researchers couldn't draw conclusions about exactly how much cured meat boosts one's risk of mania, but Yolken hopes future studies will address this.
Mania is a serious neuropsychiatric condition that's commonly identified with the so-called wild part of a bipolar mood swing and the symptoms include euphoria, insomnia, hyperactivity, risk-taking behavior, and also detachment from reality.
"We looked at a number of different dietary exposures and cured meat really stood out", Yolken told NBC News. Among that long list of questions - in what Dickerson told Live Science was not meant to be a core element of the study but rather filler to "round out" the questionnaire - was whether the patients had ever eaten cured meats.
"While a beef-based diet with added sodium nitrate resulted in mania-like behavior compared to rats consuming beef-based diet without sodium nitrate, these changes did not appear to be as severe as those resulting from consumption of nitrate-processed cured meat itself, suggesting that another factor in nitrate-processed cured meat could interact with, or worsen, the effects of dietary nitrate alone", the team stated.
Among people hospitalized for psychiatric disorders, people who ate cured meat, which included salami and various forms of dried meat sticks and jerky, had a almost 3.5 higher likelihood of having been admitted for mania, compared to people in the control group, who did not have psychiatric conditions. The study was conducted on both humans and rats and the researchers found that the rats exhibited hyperactivity, similar to the mania in humans.
The researchers then worked with a beef jerky company to create nitrate free dried beef and again a group of rats was split into two groups.
Nitrates used to cure the meats are to blame, according to experts at Johns Hopkins University School of Medicine in Baltimore.
So the researchers tried testing rats, feeding them beef jerky loaded with nitrates every other day. These animals also demonstrated changes to hippocampal pathways in the brain that have been implicated in human bipolar disorder, as well as alterations to their intestinal microbiota.
When the group analyzed the gut bacteria of the rats, they found that animals with nitrate in their diet had different bacteria in their intestines than the others.
"Our results suggest that nitrated cured meat could be one environmental player in mediating mania", she said.