THEY have always correlated 'spiritual weakness' with being 'mentally unbalanced'.
It used to be that the WT never admitted that someone who was active could ever be clinically depressed. (they were not putting Jehovah first or they wouldn't be depressed or so they indicated) and if you just had enough faith you would not need medication or assistance from mental health professionals. It was a big deal when they actually admitted that the elders were not qualified to handle all cases.
They will never admit that THEY are the ones unbalanced and in need of mental health assistance (my preference is a lobotomy for them) for all the spiritual abuses they heaped upon the willing sheep.