Nitrate-cured meats - things like beef jerky or bacon - have been linked to extensive periods of hyperactivity, insomnia, and attention loss in people experiencing manic episodes.

Research conducted by Johns Hopkins University on patients receiving care for manic symptoms found they were over three times more likely to have ever eaten processed meat products than patients being treated for other psychiatric conditions, such as schizophrenia.

"We looked at a number of different dietary exposures and cured meat really stood out," says the study's lead author Robert Yolken.

"It wasn't just that people with mania have an abnormal diet."

The exact mechanism behind the link isn't yet clear, but a follow-up experiment on rats fed jerky with their plain old rat chow resulted in increased movement and altered signalling in their hippocampus.

Changes were also noted in the rats' gut microflora, hinting at a possible stepping stone between the nitrates in the meat and effects on their nervous system.

Taken all together, the results provide a strong suggestion that a diet rich in many varieties of ham, jerky or salami just might play a role in the development of mania-related conditions in at least some people.

Bipolar disorder is a chronic mental health condition characterised by dramatic swings in mood and energy levels, including mania. Episodes can last weeks, or even months, and can coincide with depression and psychosis.

The condition affects as many as one in 25 people at some time in their life, significantly impacting productivity and taking a serious toll on personal and community wellbeing.

Surprisingly little is known about the condition's causes. There are strong hints of a genetic predisposition, though as with most neurological conditions there's a lot more going on than a wonky gene or two.

Environmental factors that affect early development, from infections to maternal smoking, have been explored as possible explanations. Stress, head injuries, and preterm births are also considered potential risk factors.

Diet is yet another area attracting significant attention, with studies suggesting a westernised diet and higher glycemic loads might contribute to the development of symptoms.

For this study, the researchers used medical records to categorise more than 700 volunteer patients as having either mania, bipolar depression, a major depressive disorder, or schizophrenia.

They gave each patient a survey that asked questions such as, "Have you ever eaten locally procured dry cured meat"? and "Have you ever eaten undercooked fish such as rare tuna?"

Those in the mania category had an unusually high number of patients who'd consumed processed meats.

"Future work on this association could lead to dietary interventions to help reduce the risk of manic episodes in those who have bipolar disorder or who are otherwise vulnerable to mania," says Yolken.

The addition of nitrogen compounds in the form of sodium nitrite or potassium nitrate has been used to preserve meats for centuries, preventing decay, adding colour and reducing oxidation.

Nitrogen compounds in meat products have been linked with cancer in the past (never forget the great Bacongate of 2015 when the World Health Organization changed the carcinogen classification of processed meats).

But in this case it's the nitrogen compounds' influence on bacteria in our gut that could end up being the culprit. And this isn't the first time nitrates in processed meats have been found to affect our health via our personal microbes.

Variations in microflora were deemed responsible for an overzealous digestion of nitrates in the diets of people who experienced migraines, causing their blood vessels to dilate more than usual and cause intense pain.

Our brains and the bacteria in our guts have a complicated relationship, one we're still learning more about as we find connections between our bugs and our emotional state, the development of Parkinson's disease, and even risk of strokes.

So, it wouldn't be a total shocker if further research confirms manic symptoms in bipolar can be exacerbated or even caused by certain microflora reacting to nitrates in our meats.

None of this means you need to ditch the jerky entirely. But to those who experience manic episodes, this might be useful information to perhaps help make their issues a little less severe.

This research was published in Molecular Psychiatry.