What type of workplace accommodations are departments required to make for a mentally unhealthy faculty member? We have a faculty member in my department who has mental health issues. These issues tend to flare up about three times a year, right at the beginning of the year, in January when grading is due and new teaching starts, and again at the end of the year when grading is due. In general these flair ups last about two weeks and are, to my understanding always accompanied by medical evidence that recommends a two week leave and a follow up evaluation after the two weeks. She is not the most mentally stable person at the best of times and I have no doubt that the additional stress from teaching and grading causes her additional issues. That said, her flare ups mean that her teaching generally gets cancelled and her grading gets reassigned. What type of accommodations does a department have to make for an individual who does not seem to be healthy enough, in this case mentally, to carry out core responsibilities and how does a department go about making those accommodations? I am interested in both legal and moral obligations and am located in the UK, to the extent that it matters.
I am only even vaguely qualified to speak on how this is ideally handled in the USA, so hopefully this will be of use at least as a starting point. I am not qualified to say anything about similarities between UK and US law on matters such as this - and I'm not a lawyer! I think this is a very important question though, and I hate to see it going without any kind of answer at all.
In the US, there are a few related but separate pieces of landmark legislation that guide workplace accommodations for &quot;serious medical conditions&quot; and &quot;disabilities&quot; (quoted because these have specific legal definitions).
First of all, the Family Medical Leave Act (FMLA):

The Family and Medical Leave Act (&quot;FMLA&quot;) provides certain employees
with up to 12 workweeks of unpaid, job-protected leave a year, and
requires group health benefits to be maintained during the leave as if
employees continued to work instead of taking leave
[...]
Leave Entitlement
A covered employer must grant an eligible employee up to a total of 12
workweeks of unpaid leave in a 12 month period for one or more of the
following reasons:
[...]

when the employee is unable to work because of a serious health condition.


There are lots of qualifying statements, but in US academia generally the FMLA applies.
FMLA TLDR;
Specifically, this means that having to take 4 weeks off a year due to any condition legally defined as a &quot;serious medical condition&quot; (related to a disability, chronic physical or mental illness - see the law specifically for the definition of these terms) is not a &quot;reasonably accommodation&quot; at all, but a legally mandated requirement. A person who takes up to 12-weeks a year of such leave has their job protected, end of story. If this is inconvenient, the legal response is: too bad - you are a big institution, you'll figure out how to make due.
In the USA, this is really a sufficient and complete answer without considering reasonable accommodations, because taking medically necessary time off isn't considered as such.
But let's go further, because more is morally and often legally required.
Get Proactive: Reasonable Accommodations, the Equal Employment Opportunity Commission (EEOC), and the Americans With Disability Act (ADA)
In the US, a qualifying employee has the the right to &quot;reasonable accommodations&quot;. OK - what the heck is reasonable? I'm a big fan of the Job Accommodations Network (JAN) materials, as they are much easier to read and understand than most other materials.

III.THE REASONABLE ACCOMMODATION OBLIGATION
3.1 Overview of Legal Obligations

An employer must provide a reasonable accommodation to the known physical or mental limitations of a qualified applicant or employee
with a disability unless it can show that the accommodation would
impose an undue hardship on the business.
Reasonable accommodation is any modification or adjustment to a job, an employment practice, or the work environment that makes it possible
for an individual with a disability to enjoy an equal employment
opportunity.
The obligation to provide a reasonable accommodation applies to all aspects of employment. This duty is ongoing and may arise any time
that a person's disability or job changes.
An employer cannot deny an employment opportunity to a qualified applicant or employee because of the need to provide reasonable
accommodation, unless it would cause an undue hardship.
An employer does not have to make an accommodation for an individual who is not otherwise qualified for a position.
Generally, it is the obligation of an individual with a disability to request a reasonable accommodation.
A qualified individual with a disability has the right to refuse an accommodation. However, if the individual cannot perform the essential
functions of the job without the accommodation, s/he may not be
qualified for the job.
If the cost of an accommodation would impose an undue hardship on the employer, the individual with a disability should be given the
option of providing the accommodation or paying that portion of the
cost which would constitute an undue hardship.


So, what is and isn't reasonable? According to JAN:


What accommodations are not considered reasonable?

Reasonable accommodation does not include removing essential job
functions, creating new jobs, and providing personal need items such
as eye glasses and mobility aids. Nothing in the ADA prohibits
employers from providing these types of accommodations; they simply
are not required accommodations.

What is an essential job function? There is no easy answer, but that same page quoted above provides an in-depth discussion, however I posit this reasonable rule of thumb: something is reasonable if it is not disproportionately costly, and especially if other people in a similar position have such an arrangement. If you aren't sure, get a proper Job Evaluation performed by a competent professional (your institution had better already have one on hand!).
Many professors have grad students perform a large amount of grading (with oversight and some supervision) and often use a proctor to deliver tests, for instance - so to insist that a standard way of working for other professors is not reasonable would strain the credulity of the average person (and likely any judges or review boards, should a complaint arise). On the other hand, utterly exempting a person from duties that fill a large portion of an employees work load is probably going too far.
The law in the US is often intentionally vague in this regard, for a very good reason! The goal is actively to encourage people to think of ways to craft jobs and requirements that allow anyone with a disability or chronic condition to be gainfully employed and contribute to their communities in the greatest way possible. If this means a little re-arranging or change, great - that is way cheaper than someone getting fired or having to take legal actions against an institution. With some vagueness and a &quot;reasonable person&quot; standard that is common in American law, this is hoped to actively encourage people to reach out a bit farther than they usually might to find a solution that works for everyone involved.
Proscriptive Moral Advice
As an institution/department, it is generally wise to recognize a pattern and reach out to solve an underlying problem. If a build-up of stress causes incapacitation and certain reliable intervals, maybe something can be arranged to reduce the stress during these times and avoid the worst flare ups entirely? When not possible, planning proactively can wonderfully mitigate the pain in the future; implicitly relying on no one getting ill or sick during high-stress times of the year is a masochistic assumption!
It is reasonable (and often advised) to seek out if a reasonable accommodation could be helpful and welcomed by someone with a serious condition or disability. A willingness to think creatively and to find a solution that everyone can be happy about is ideal.
If a huge glut of work at certain times of the years causes anxiety, can this workload be made more manageable and less all-at-once? Are department requirements/demands worsening things and creating a more difficult environment than necessary? Electronic grading systems/options, automated fill-in-the-bubble grading, Teaching Assistants to do some of the grading (when appropriate to the work), Proctors (such as by giving the tests in some classes so the professor can use that time for grading other tests/assignments instead), and staggered test schedules are widely used to varying degrees throughout the world and can be potentially helpful. Can other duties be rescheduled, such as certain evaluations, meetings, etc, to better even out the work flow?
It is possible that one person's illness can be used as a tool to improve everyone's work conditions and satisfaction, by allowing a &quot;suck it up and deal with it&quot; approach that was begrudgingly accepted to be challenged and overhauled. Empathy and compassion - understanding that someone would almost invariably be happy to not be ill - and realizing that the problems of having more work foisted on everyone when someone is ill is often the fault of the work system rather than on one well-intentioned individual, can make some amazing progress possible.