To quote -

> About 1 in 5 adults has a mental illness in any given year

This talks about people who may already have mental illness -

> Mental illness can begin at any age, from childhood through later adult years, but most cases begin earlier in life.

The OP is about new cases...

Take out a sketchpad, draw an exponential representing the # of COVID cases everyday, over 90 days. The area under that curve / 5 is the number of new mental illness patients added every 90 days. Now extrapolate that over the year, and add it to the 1/5 (Total population) number, and that's where it starts to sound alarming.

Commenters are mostly overlooking the bidirectional element in the study.

A psychiatric diagnosis in the previous year was associated with a higher incidence of COVID-19 diagnosis (relative risk 1·65, 95% CI 1·59–1·71; p<0·0001)

https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0...

Now THAT's interesting. Speculations about why? Are more anxious people more likely to get tested for covid? Depressed people more likely to not care about exposure?

I'm pretty sure anxiety affects the immune system (a quick search seems to confirm that), so that might play a part

Even the 1/5 general population has to develop it at some point. Sounds like covid patients are converging towards the normal after recovery, so I don't really see an issue here.

1/5 of the general population do not develop mental illnesses within 90 days of an arbitrary starting point, unless the mental illness is extremely short-lived.

Think of the difference this way:

If 1/100 people are currently experiencing a headache, then it's also reasonable to think that 1/100 people will experience a headache tomorrow.

But if 1/100 people have an amputation, it does not follow that 1/100 people will get an amputation tomorrow, or even in the next 90 days. If 1/100 people were always getting an amputation within 90 days of any arbitrary starting point, there would be many, many more amputees around.

Mental illness being something that may lasts months to years, this certainly seems to be closer to the amputation case than the headache case. That implies that getting Covid can, indeed, be said to increase your chance of developing mental illness.

No the OP is about newly diagnosed cases.

This is a major difference!

Care to elaborate?

It's e.g. not uncommon for people to go into some form of denial of their (new/worsens) mental illness, it they are simple not aware that a mental illness can have given effects.

This makes it super hard to differentiate between something causing mental illness and that something in some way making people being diagnosed with it.

E.g. the current works situation makes it much simpler for people to get depression and anxiety without being infected by Covid-19, but due to the circumstances if someone got a new (or worsens) mental illness and covid in 2020 it's likely that they will diagnosed the illness after having had covid even if it came from the world situation not the covid virus directly.

Example Unrelated to covid: I got diagnosed ~3years after it (slowly) started to mess up my life, but that was when it started to noticably affect my life. As far as I can tell before that I had it in a mild version for like and addition 7-10 years.

So the time where sunshine is diagnosed as mentally ill isn't necessary at all related to when that person got mentally ill.

Aren't COVID patients way more likely to receive medical care than other diseases, many of whom might self treat in order to avoid contracting COVID?

This helps a lot, thank you!

According to the article it was twice as likely as non-Covid patients.

And this year is not "a given year"

The research is on "anxiety and depression" which is increasing in non-COVID-19 patients this year.

90 days vs 1 year?

Yeah, agree, but how do we compare time slices over probability?

In a back-of-the-napkin, spherical-cow, way, it's not too hard.

20% chance it happens in a year means an 80% chance it doesn't. Let's assume (this is the spherical cow) each day has the same chance. We can find it by looking at the chance an adult doesn't get a mental illness in a year. Then, because that's the chance they won't get it every day, it's easier to figure out the daily chance of not getting one.

    0.8 = x^365
    x = 0.8^(1/365)
    x = 0.9993888346422956
    1 - x = 0.0006111653577044462

So, overall, adults have roughly a 0.061% chance each day of getting a mental illness.

Compared to the daily risk for this 90-day period

    0.8 = x^90
    x = 0.8^(1/90)
    x = 0.9993888346422956
    1 - x = 0.0024763016863216247 

So about 0.248% each day for the COVID patients. That's more than four times as high as for all adults.

Remember, this is spherical cow stuff. Numbers to use in other calculations need a more experienced statistical approach, I'm sure. But this at least tells us something's different.

As a sanity check the "half as high" background number sounds high?

edit: scratch my mistaken numbers - but people would normally (without covid) get many mental illnesses per lifetime?

That's tricky, agreed. One chance in 1000 every day adds up to a 30% chance in a year for instance.

And 1-in-5 every 90 days equals 4-in-5 over a year. If the risk doesn't change over time (if the covid effect is persistent for a year)

> (if the covid effect is persistent for a year)

I think that's the important bit. The article (at least) didn't indicate that the same standard applies at the 180, 270, or 360 day mark, so I don't think we can just say COVID patients roll the dice on mental illness 4x as often as the general population. If that's actually being implied, it's horrible.

I feel like you'd probably want to use a Poisson distribution for this, but I can't be bothered to work it out fully.