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DEAR DR. ROACH: In a recent column, you OK'd stevia, which I had heard could negatively impact our microbiomes. I am borderline prediabetic, and I had stopped using stevia accordingly. However, I hate unsweetened coffee. Can you comment on stevia's impact on our microbiomes in your column? -- M.M.

ANSWER: I wish I could give you an answer that everyone would agree with, but the literature is conflicting. I found a well-done trial from 2024 showing that there were no significant changes in the microbiome (a term for the whole complex array of bacteria and other tiny life forms in our intestines) among volunteers taking five drops of stevia twice daily for 12 weeks.

Another study (from before the trial) showed increased diversity in a laboratory model, which is generally a good thing. Finally, a 2022 analysis of all trials found no evidence of harm to the microbiome. Based on this, I think it unlikely that stevia has a serious adverse effect on the microbiome.

Multiple studies have found that sugar has adverse effects on the microbiome, so if your main concerns are diabetes and your microbiome, the evidence at the present time supports stevia rather than sugar in your coffee.

DEAR DR. ROACH: Our adult daughter was recently diagnosed with COVID psychosis. Evidently, it is so rare that many people, including medical personnel, have never heard of it. She is being held in a mental facility where she is in a manic state most of the time and very psychotic. She is finally taking her medicine, so she seems to be returning back to herself.

Do you have any information on this condition? Is it curable? Will she ever be able to return to her normal existence? They are wanting to release her, but we have yet to talk to any doctor or nurse who can just explain what the prognosis is. -- H.M.

ANSWER: Because so many people were diagnosed with COVID, there have been many reports of conditions that occurred after the infection. However, it can be hard to determine whether these happened by chance or whether they were due to the infection.

Well-designed studies to determine whether the risk of an outcome is higher after an infection have been done for many conditions, and there are quite a few conditions that a person is clearly at a higher risk for after a bout of COVID-19. These are sometimes called "long COVID" symptoms. However, it isn't completely clear whether psychosis is related to COVID, although I think it is likely.

Common symptoms of psychosis include hallucinations (often auditory); delusions (fixed, false beliefs); disorganized speech (often tangential to the point where it's hard to keep track of what they are saying); and disorganized behavior, especially an inability to keep oneself properly dressed and cleaned.

I did find a 2023 review of 57 cases of COVID psychosis, two-thirds of whom had never had any symptoms of psychiatric disease before their bout of COVID. (The authors noted that COVID isn't unique, and other infections such as influenza also have an increased risk of psychosis.) The average range of people with a diagnosis of COVID psychosis was the 40s.

COVID is known to affect many pathways in the brain through low oxygen levels, inflammation, and an enzyme called ACE2. It is reasonable to think that these changes could result in multiple psychiatric symptoms. As far as a prognosis, over 70% of the cases resulted in a complete recovery, but most people with this condition required antipsychotic drugs. (Though they were able to get off of the drugs.)

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.

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