Lowercase Letter in Brackets [duplicate]

Please look at the following sentence with the bracketed lowercase letter.

“Doctor Rogers' thesis states that ‘[p]atients often display psychosomatic symptoms.’ ” Is the author decapitalizing the word "patients" that may have appeared in the original, and he or she is denoting this via use of the brackets around the letter "p"? In your opinion, did the original appear like this (see below) with the unnecessary capitalization of the word "patients"?

“Doctor Rogers' thesis states that ‘Patients often display psychosomatic symptoms.’ ”

Thank you.

No, in the thesis written by Dr. Rogers, the sentence probably read:

Patients often display psychosomatic symptoms.

or perhaps more probably, something along the lines of:

Patients often display psychosomatic symptoms when...

(The part about "Doctor Rogers' thesis states that..." was likely NOT in the thesis.)

So, when the author cites the thesis:

Doctor Rogers' thesis states that ‘[p]atients often display psychosomatic symptoms.’

it's shifted to lower-case p, since it's no longer at the start of the sentence, and put in [brackets], to indicate a difference from the original.