An ignorant and unkind statement. The brain of a depressed person fails to produce the right chemicals, much as type one diabetes is caused by the pancreas being unable to produce insulin.
A-Men, it's amazing how much some people think they know but in reality do not know.
Though you might like this:
“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.”
....Mark Twain