Is career mismatch a cause of burnout?

The short answer is yes.

But it is complex.

Careers can start out as a good match and become less so over time ( secondary career mismatch)
And sometimes the career was never a good match right at the start ( primary career mismatch)

A match between person and post is sometimes assumed by individual and employer - only to become obviously not a match over  time.

And sometimes there is no real career mismatch at the bottom of burnout.... it just feels as if it is.

A career that matches a person well is a different issue to individual posts within that career that match well. For example a person can be well matched to a career in medicine but not well matched to being a GP.

The whole issue of matching oneself to a career or post and whether burnout is then more or less likely to arise is only part of a much bigger picture. That said - when assessing burnout we always look at career mismatch as a potential contributing factor.

The journey towards burnout is not anywhere near as linear as this sketch might at first suggest.
So unravelling burnout - the causes, the development, the ups and downs of why it has come about it - is a very convoluted process but can be made considerably easier with the right input at the right time.